KNOT Offshore Partners (KNOP) 6-K 26 Aug 21 2021 Q2 Current report (foreign) Financial data

Document and Entity Information

Document and Entity Information	6 Months Ended
	Jun. 30, 2021
Document And Entity Information
Document Type	6-K
Entity Registrant Name	KNOT Offshore Partners LP
Entity Central Index Key	0001564180
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity File Number	001-35866
Entity Address, Address Line One	2 Queen’s Cross,
Entity Address, Postal Zip Code	AB15 4YB
Entity Address, City or Town	Aberdeen, Aberdeenshire
Entity Address, Country	GB
Current Fiscal Year End Date	--12-31
Amendment Flag	false

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating revenues: (Notes 3, 4 and 13)
Time charter and bareboat revenues	$ 66,513	$ 70,250	$ 132,111	$ 137,476
Loss of hire insurance recoveries (Note 5)	4,397		10,279
Other income	27	9	28	607
Total revenues	70,937	70,259	142,418	138,083
Operating expenses: (Note 13)
Vessel operating expenses	17,394	13,112	35,954	28,746
Depreciation	23,831	22,451	47,515	44,824
Write-down (Note 19)	29,421		29,421
General and administrative expenses	1,492	1,337	3,113	2,724
Total operating expenses	72,138	36,900	116,003	76,294
Operating income (loss)	(1,201)	33,359	26,415	61,789
Finance income (expense):
Interest income		3		121
Interest expense (Note 6)	(6,804)	(8,512)	(14,176)	(18,974)
Other finance expense (Note 6)	(250)	(199)	(409)	(307)
Realized and unrealized gain (loss) on derivative instruments (Note 7)	(2,265)	(3,092)	5,746	(26,782)
Net gain (loss) on foreign currency transactions	(144)	127	(96)	(297)
Total finance expense	(9,463)	(11,673)	(8,935)	(46,239)
Income (loss) before income taxes	(10,664)	21,686	17,480	15,550
Income tax benefit (Note 9)	(261)	(3)	(264)	(6)
Net income (loss)	(10,925)	21,683	17,216	15,544
Series A Preferred unitholders' interest in net income	1,759	1,800	3,559	3,600
General Partner's interest in net income	(233)	368	253	221
Limited Partners' interest in net income	$ (12,451)	$ 19,515	$ 13,404	$ 11,723
Earnings per unit (Basic): (Note 15)
General Partner unit (basic)	$ (0.38)	$ 0.60	$ 0.41	$ 0.36
Earnings per unit (Diluted): (Note 15)
General Partner unit (basic)	(0.38)	0.60	0.41	0.36
Common Units
Earnings per unit (Basic): (Note 15)
Common unit (basic)	(0.38)	0.60	0.41	0.36
Earnings per unit (Diluted): (Note 15)
Common unit (diluted)	$ (0.38)	$ 0.58	$ 0.41	$ 0.36

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Condensed Consolidated Statements of Comprehensive Income
Net income (loss)	$ (10,925)	$ 21,683	$ 17,216	$ 15,544
Comprehensive income (loss)	$ (10,925)	$ 21,683	$ 17,216	$ 15,544

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands		Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents (Note 8)		$ 51,589	$ 52,583
Amounts due from related parties (Note 13)		1,762	5,726
Inventories		3,264	2,652
Other current assets (Note 18)		14,381	5,511
Total current assets		70,996	66,472
Long-term assets:
Vessels, net of accumulated depreciation and impairment (Notes 8, 10 and 19)		1,642,026	1,708,786
Right-of-use assets (Note 4)		3,061	1,490
Intangible assets, net (Note 11)		378	681
Derivative assets (Notes 7 and 8)		168
Accrued income		2,164	2,867
Total long term assets		1,647,797	1,713,824
Total assets		1,718,793	1,780,296
Current liabilities:
Trade accounts payable (Note 13)		3,804	3,848
Accrued expenses		5,866	5,380
Current portion of long-term debt (Notes 8 and 12)		351,370	184,188
Current lease liabilities (Note 4)		641	652
Current portion of derivative liabilities (Notes 7 and 8)		9,984	10,695
Income taxes payable		276	86
Current portion of contract liabilities (Note 11)		1,518	1,518
Prepaid charter		7,821	5,424
Amount due to related parties (Note 13)		3,450	2,140
Total current liabilities		384,730	213,931
Long-term liabilities:
Long-term debt (Notes 8 and 12)		646,348	846,157
Lease liabilities (Note 4)		2,419	838
Derivative liabilities (Notes 7 and 8)		8,495	19,358
Contract liabilities (Note 11)		1,410	2,168
Deferred tax liabilities (Note 9)		294	295
Total long-term liabilities		658,966	868,816
Total liabilities		1,043,696	1,082,747
Commitments and contingencies (Note 14)
Series A Convertible Preferred Units (1)	[1]	84,367	89,264
Partners' capital:
Common unitholders		580,248	597,390
General partner interest		10,482	10,895
Total partners' capital		590,730	608,285
Total liabilities and equity		$ 1,718,793	$ 1,780,296
[1]	On May 27, 2021, Tortoise Direct Opportunities Fund LP, the holder of 416,677 of the Partnership’s Series A Convertible Preferred Units, sold 208,333 of its Series A Preferred Units to KNOT and converted 208,334 Series A Preferred Units to 215,292 common units based on a conversion rate of 1.0334 .

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical)	May 27, 2021shares	Jun. 30, 2021shares
Shares converted		(208,334)
Common Units
Shares converted		215,292
Tortoise Direct Opportunities Fund LP | Common Units
Shares converted	215,292
Conversion rate	1.0334
Series A Convertible Preferred Units | Tortoise Direct Opportunities Fund LP
Shares held	416,677
Shares sold	208,333
Shares converted	208,334

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Changes in Partners' Capital - USD ($) $ in Thousands		General Partner Units	Common Units	Total
Beginning balance at Dec. 31, 2019		$ 11,155	$ 611,241	$ 622,396
Net income (loss)		221	11,723	11,944
Cash distributions		(666)	(35,402)	(36,068)
Ending balance at Jun. 30, 2020		10,710	587,562	598,272
Convertible preferred units, beginning balance at Dec. 31, 2019				89,264
Net income				3,600
Cash distributions				(3,600)
Convertible preferred units, ending balance at Jun. 30, 2020				89,264
Beginning balance at Mar. 31, 2020		10,675	585,748	596,423
Net income (loss)		368	19,515	19,883
Cash distributions		(333)	(17,701)	(18,034)
Ending balance at Jun. 30, 2020		10,710	587,562	598,272
Convertible preferred units, beginning balance at Mar. 31, 2020				89,264
Net income				1,800
Cash distributions				(1,800)
Convertible preferred units, ending balance at Jun. 30, 2020				89,264
Beginning balance at Dec. 31, 2020		10,895	597,390	608,285
Net income (loss)		253	13,404	13,657
Cash distributions		(666)	(35,402)	(36,068)
Conversion of preferred units to common units	[1]		4,856	4,856
Ending balance at Jun. 30, 2021		10,482	580,248	590,730
Convertible preferred units, beginning balance at Dec. 31, 2020	[2]			89,264
Conversion of preferred units to common units	[1]			(4,856)
Net income				3,559
Cash distributions				(3,600)
Convertible preferred units, ending balance at Jun. 30, 2021	[2]			84,367
Beginning balance at Mar. 31, 2021		11,048	605,544	616,592
Net income (loss)		(233)	(12,451)	(12,684)
Cash distributions		(333)	(17,701)	(18,034)
Conversion of preferred units to common units	[1]		4,856	4,856
Ending balance at Jun. 30, 2021		$ 10,482	$ 580,248	590,730
Convertible preferred units, beginning balance at Mar. 31, 2021				89,264
Conversion of preferred units to common units	[1]			(4,856)
Net income				1,759
Cash distributions				(1,800)
Convertible preferred units, ending balance at Jun. 30, 2021	[2]			$ 84,367
[1]	On May 27, 2021, Tortoise Direct Opportunities Fund LP, the holder of 416,677 of the Partnership’s Series A Convertible Preferred Units, sold 208,333 of its Series A Preferred Units to KNOT and converted 208,334 Series A Preferred Units to 215,292 common units based on a conversion rate of 1.0334 .
[2]	On May 27, 2021, Tortoise Direct Opportunities Fund LP, the holder of 416,677 of the Partnership’s Series A Convertible Preferred Units, sold 208,333 of its Series A Preferred Units to KNOT and converted 208,334 Series A Preferred Units to 215,292 common units based on a conversion rate of 1.0334 .

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Changes in Partners' Capital (Parenthetical)	May 27, 2021shares	Jun. 30, 2021shares
May 27, 2021: Conversion of Series A Preferred Units		(208,334)
Common Units
May 27, 2021: Conversion of Series A Preferred Units		215,292
Tortoise Direct Opportunities Fund LP | Common Units
May 27, 2021: Conversion of Series A Preferred Units	215,292
Conversion rate	1.0334
Tortoise Direct Opportunities Fund LP | Series A Convertible Preferred Units
Shares held	416,677
Shares sold	208,333
May 27, 2021: Conversion of Series A Preferred Units	208,334

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
OPERATING ACTIVITIES
Net income	$ (10,925)	$ 21,683	$ 17,216	$ 15,544
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation	23,831	22,451	47,515	44,824	$ 89,743
Write-down related to vessel	29,421		29,421
Amortization of contract intangibles / liabilities			(456)	(456)
Amortization of deferred debt issuance cost	656	626	1,758	1,262
Drydocking expenditure			(3,428)	(2,666)
Income tax expense	261	3	264	6
Income taxes paid			(74)	(78)
Interest expenses			12,418	18,974
Interest paid			(12,571)	(18,888)
Unrealized (gain) loss on derivative instruments			(11,742)	26,685
Unrealized (gain) loss on foreign currency transactions			27	(56)
Changes in operating assets and liabilities:
Decrease (increase) in amounts due from related parties			3,964	959
Decrease (increase) in inventories			(613)	50
Decrease (increase) in other current assets			(8,929)	(699)
Decrease (increase) in accrued revenue			703	551
Increase (decrease) in trade accounts payable			(8)	(198)
Increase (decrease) in accrued expenses			640	(1,947)
Increase (decrease) prepaid charter			2,399	(3,116)
Increase (decrease) in amounts due to related parties			1,310	38
Net cash provided by operating activities			79,814	80,789
INVESTING ACTIVITIES
Net cash used in investing activities			(6,748)	(216)
FINANCING ACTIVITIES
Proceeds from long-term debt			99,300
Repayment of long-term debt			(132,208)	(42,973)
Payment of debt issuance cost			(1,478)	(13)
Cash distribution			(39,668)	(39,668)
Net cash used in financing activities			(74,054)	(82,654)
Effect of exchange rate changes on cash			(6)	(8)
Net increase (decrease) in cash and cash equivalents			(994)	(2,089)
Cash and cash equivalents at the beginning of the period			52,583	43,525	43,525
Cash and cash equivalents at the end of the period	$ 51,589	$ 41,436	51,589	41,436	$ 52,583
Property, Plant and Equipment, Excluding Acquired Vessels
INVESTING ACTIVITIES
Disposals (additions) to vessel and equipment			$ (6,748)	$ (216)

Description of Business

Description of Business	6 Months Ended
	Jun. 30, 2021
Description of Business
Description of Business	1) Description of Business KNOT Offshore Partners LP (the “Partnership”) was formed as a limited partnership under the laws of the Republic of the Marshall Islands. The Partnership was formed for the purpose of acquiring 100% ownership interests in four shuttle tankers owned by Knutsen NYK Offshore Tankers AS (“KNOT”) in connection with the Partnership’s initial public offering of its common units (the “IPO”), which was completed on April 15, 2013. As of June 30, 2021, the Partnership had a fleet of seventeen shuttle tankers, the Windsor Knutsen Bodil Knutsen Recife Knutsen Fortaleza Knutsen Carmen Knutsen, Hilda Knutsen, Torill Knutsen Dan Cisne Dan Sabia, Ingrid Knutsen Raquel Knutsen, Tordis Knutsen, Vigdis Knutsen, Lena Knutsen Brasil Knutsen Anna Knutsen Tove Knutsen The consolidated financial statements have been prepared assuming that the Partnership will continue as a going concern. The Partnership expects that its primary future sources of funds will be available cash, cash from operations, borrowings under any new loan agreements and the proceeds of any equity financings. The Partnership believes that these sources of funds (assuming the current rates earned from existing charters) will be sufficient to cover operational cash outflows and ongoing obligations under the Partnership’s financing commitments to pay loan interest and make scheduled loan repayments and to make distributions on its outstanding units. Accordingly, as of August 26, 2021, the Partnership believes that its current resources, including the undrawn portion of its revolving credit facilities of $50 million, are sufficient to meet working capital requirements for its current business for at least the next twelve months.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2) Summary of Significant Accounting Policies (a) Basis of Preparation The accompanying unaudited condensed consolidated interim financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the U.S. Securities and Exchange Commission (the “SEC”) for interim financial information. In the opinion of management of the Partnership, all adjustments considered necessary for a fair presentation, which are of normal recurring nature, have been included. All intercompany balances and transactions are eliminated. The unaudited condensed consolidated financial statements do not include all the disclosures and information required for a complete set of annual financial statements; and, therefore, these unaudited condensed consolidated financial statements should be read in conjunction with the Partnership’s audited consolidated financial statements for the year ended December 31, 2020, which are included in the Partnership’s Annual Report on Form 20-F (the “2020 20-F”). Vessels and Equipment Historically, the useful life of the Partnership’s vessels and equipment was assessed as 25 years commencing from the date the vessel and equipment were delivered from the shipyard. As of June 30, 2021, the Partnership has considered factors related to the ongoing use of the vessels and equipment, gradual shifts in market conditions and other long-term factors associated with the global oil and maritime transportation industries and based on this has reassessed the useful life as being 23 years. This change in estimate will be applied prospectively from July 1, 2021 and impacts the entire fleet of shuttle tanker vessels. The change in estimate did however not impact income, net income nor earnings per share basic and diluted for the three and six months ended June 30, 2021. (b) Significant Accounting Policies The accounting policies adopted in the preparation of the unaudited condensed consolidated interim financial statements are consistent with those followed in the preparation of the Partnership’s audited consolidated financial statements for the year ended December 31, 2020, as contained in the Partnership’s 2020 20-F. (c) Recent Accounting Pronouncements Adoption of new accounting standards No new accounting standards have recently been adopted. Accounting pronouncements not yet adopted In March 2020, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2020-04 Reference Rate Reform (Topic 848), Facilitation of the Effects of Reference Rate Reform on Financial Reporting. The update provides temporary optional expedients and exceptions to the guidance in US GAAP on contract modifications and hedge accounting, to ease the financial reporting burdens related to the expected market transition from the London Interbank Offered Rate (LIBOR) and other interbank offered rates to alternative reference rates. For all types of hedging relationships, the guidance allows an entity to change the reference rate and other critical terms related to reference rate reform without having to dedesignate the relationship. The guidance is effective upon issuance through December 31, 2022. Although the Partnership does not apply hedge accounting, the Partnership has debt and interest rate swaps that reference LIBOR. The Partnership is evaluating the impact of the guidance on the consolidated financial statements. Other recently issued accounting pronouncements are not expected to materially impact the Partnership.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2021
Segment Information
Segment Information	3) Segment Information The Partnership has not presented segment information as it considers its operations to occur in one reportable segment, the shuttle tanker market. As of June 30, 2021 and 2020, the Partnership’s fleet consisted of seventeen vessels and sixteen vessels, respectively, and operated under time charters and bareboat charters. Under the time charters and bareboat charters, the charterer, not the Partnership, controls the choice of which trading areas the applicable Vessel will serve. Accordingly, the Partnership’s management, including the chief operating decision makers, does not evaluate performance according to geographical region. The following table presents time charter and bareboat revenues and percentages of revenues for material customers that accounted for more than 10% of the Partnership’s consolidated revenues during the three and six months ended June 30, 2021 and 2020. All of these customers are subsidiaries of major international oil companies. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ (U.S. Dollars in thousands) 2021 2020 2021 2020 ​ Eni Trading and Shipping S.p.A. ​ $ 10,915 16 % $ 10,953 16 % $ 21,748 16 % $ 22,088 16 % Fronape International Company, a subsidiary of Petrobras Transporte S.A. ​ 11,249 17 % 11,249 16 % 22,378 17 % 22,498 16 % Repsol Sinopec Brasil, S.A., a subsidiary of Repsol Sinopec Brasil, B.V. ​ 9,282 14 % 9,285 13 % 18,075 14 % 15,178 11 % Brazil Shipping I Limited, a subsidiary of Royal Dutch Shell ​ 16,168 24 % 20,512 29 % 32,156 24 % 41,236 30 % Galp Sinopec Brasil Services B.V. ​ 8,881 13 % 8,881 13 % 17,665 13 % 17,763 13 % ​ The Partnership has financial assets that expose it to credit risk arising from possible default by a counterparty. The Partnership considers its counterparties to be creditworthy banking and financial institutions and does not expect any significant loss to result from non-performance by such counterparties. The maximum loss due to credit risk that the Partnership would incur if counterparties failed completely to perform would be the carrying value of cash and cash equivalents, and derivative assets. The Partnership, in the normal course of business, does not demand collateral from its counterparties.

Operating Leases

Operating Leases	6 Months Ended
	Jun. 30, 2021
Operating Leases
Operating Leases	4) Operating Leases Revenues The Partnership's primary source of revenues is chartering its shuttle tankers to its customers. The Partnership uses two types of contracts, time charter contracts and bareboat charter contracts. The Partnership's time-charter contracts include both a lease component, consisting of the bareboat element of the contract, and non-lease component, consisting of operation of the Vessel for the customers, which includes providing the crewing and other services related to the Vessel's operations, the cost of which is included in the daily hire rate, except when off hire. The following table presents the Partnership's revenues by time charter and bareboat charters and other revenues for the three and six months ended June 30, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (U.S. Dollars in thousands) 2021 2020 2021 2020 Time charter revenues (service element included) ​ $ 55,264 ​ $ 59,001 ​ $ 109,733 ​ $ 114,978 Bareboat revenues ​ ​ 11,249 ​ ​ 11,249 ​ ​ 22,378 ​ ​ 22,498 Other revenues (loss of hire insurance recoveries and other income) ​ 4,424 ​ 9 ​ 10,307 ​ 607 Total revenues ​ $ 70,937 ​ $ 70,259 ​ $ 142,418 ​ $ 138,083 ​ As of June 30, 2021, the minimum contractual future revenues to be received from time charters and bareboat charters during the next five years and thereafter are as follows (including service element of the time charter, but excluding unexercised customer option periods): ​ ​ ​ ​ ​ (U.S. Dollars in thousands) ​ ​ 2021 (excluding the six months ended June 30, 2021) ​ $ 131,436 2022 ​ ​ 184,259 2023 ​ ​ 99,805 2024 ​ ​ 102,560 2025 ​ ​ 76,916 2026 and thereafter ​ ​ 46,775 Total $ 641,751 ​ The minimum contractual future revenues should not be construed to reflect total charter hire revenues for any of the years. Minimum contractual future revenues are calculated based on certain assumptions such as operating days per year. In addition, minimum contractual future revenues presented in the table above have not been reduced by estimated off-hire time for periodic maintenance. The amounts may vary given unscheduled future events such as vessel maintenance. The Partnership’s fleet as of June 30, 2021 consisted of: ● the Fortaleza Knutsen , a shuttle tanker built in 2011 that is currently operating under a bareboat charter that expires in March 2023 with Fronape International Company, a subsidiary of Petrobras Transporte S.A. (“Transpetro”); ● the Recife Knutsen , a shuttle tanker built in 2011 that is currently operating under a bareboat charter that expires in August 2023 with Transpetro; ● the Bodil Knutsen , a shuttle tanker built in 2011 that is currently operating under a time charter with Knutsen Shuttle Tankers Pool AS, a subsidiary of KNOT, for an initial three-month period commencing on May 13, 2021 and then on a rolling one-month basis, possibly for the remainder of 2021. The vessel is expected to undergo installation of a VOC recovery plant in the third or fourth quarter of 2021 and will commence on a new time charter contract with a major oil company in the fourth quarter of 2023 or the first quarter of 2024 ; ● the Windsor Knutsen , a conventional oil tanker built in 2007 and retrofitted to a shuttle tanker in 2011. The Windsor Knutsen has been idle since December 2020, other than for a short-term voyage of seven days. The vessel is expected to operate under a one-year time charter contract (with owner's option to substitute, and with charterer's options to extend the charter by one one-year period and then one six-month period) with a major oil company. The charter is expected to commence in September 2021. The signing of this contract remains outstanding pending a number of final details which are expected to be resolved shortly; ● the Carmen Knutsen , a shuttle tanker built in 2013 that is currently operating under a time charter that expires in January 2023 , with Repsol Sinopec Brasil, B.V. a subsidiary of Repsol Sinopec Brasil, S.A. (“Repsol”), with options to extend until January 2026 ; ● the Hilda Knutsen , a shuttle tanker built in 2013 that is currently operating under a time charter that expires in August 2022 with Eni Trading and Shipping S.p.A. (“ENI”), with options to extend until August 2025 ; ● the Torill Knutsen , a shuttle tanker built in 2013 that is currently operating under a time charter that expires in November 2022 with ENI, with options to extend until November 2024 ; ● the Dan Cisne , a shuttle tanker built in 2011 that is currently operating under a bareboat charter that expires in September 2023 with Transpetro; ● the Dan Sabia , a shuttle tanker built in 2012 that is currently operating under a bareboat charter that expires in January 2024 with Transpetro; ● the Ingrid Knutsen , a shuttle tanker built in 2013 that is currently operating under a time charter that expires in February 2024 with Vår Energi Marine AS, a Norwegian subsidiary of Vår Energi AS, with options to extend until February 2029 ; ● the Raquel Knutsen , a shuttle tanker built in 2015 that is currently operating under a time charter that expires in June 2025 with Repsol, with options to extend until June 2030 ; ● the Tordis Knutsen , a shuttle tanker built in 2016 that is currently operating under a time charter that expires in January 2022 , with a subsidiary of Shell. The vessel will commence on a new 3 -year time charter contract with a major oil company in 2023 ; ● the Vigdis Knutsen , a shuttle tanker built in 2017 that is currently operating under a time charter that expires in the second quarter of 2022 with a subsidiary of Shell. The vessel will commence on a new 3 -year time charter contract with a major oil company in 2023 ; ● the Lena Knutsen , a shuttle tanker built in 2017 that is currently operating under a time charter that expires in the third quarter of 2022 with a subsidiary of Shell. The vessel will commence on a new 3 -year time charter contract with a major oil company in 2023 ; ● the Brasil Knutsen , a shuttle tanker built in 2013 that is currently operating under a time charter that expires in September 2022 with Galp Sinopec Brazil Services B.V. (“Galp”), with options to extend until September 2028 ; and ● the Anna Knutsen , a shuttle tanker built in 2017 that is currently operating under a time charter that expires in March 2022 with Galp, with options to extend until March 2028 . ● the Tove Knutsen , a shuttle tanker built in 2020 that is currently operating under a time charter that expires in October 2027 with Equinor, with options to extend until October 2040 . Lease obligations The Partnership does not have any material leased assets but has some leased equipment on operational leases on the various ships operating on time charter contracts. As of June 30, 2021, the right-of-use asset and lease liability for operating leases A maturity analysis of the Partnership’s lease liabilities from leased-in equipment as of June 30, 2021 is as follows: ​ ​ ​ ​ ​ (U.S. Dollars in thousands) ​ 2021 (excluding the six months ended June 30, 2021) ​ $ 352 2022 ​ 703 2023 ​ 703 2024 ​ 703 2025 ​ ​ 703 2026 and thereafter ​ ​ 59 Total ​ $ 3,223 Less imputed interest ​ 163 Carrying value of operating lease liabilities ​ $ 3,060 ​

Insurance Proceeds

Insurance Proceeds	6 Months Ended
	Jun. 30, 2021
Insurance Proceeds
Insurance Proceeds	5) Insurance proceeds Windsor Knutsen In December 2020, the Windsor Knutsen 14 million, respectively, for loss of hire proceeds which were recorded as a component of total revenues since day rates are recovered under the terms of the policy. In addition, for the three and six months ended June 30, 2021, the Partnership recorded $2.5 million and $4.1 million, respectively, for recoveries up to the amount of loss under hull and machinery insurance for repairs as a result of the engine block damage to the Windsor Knutsen. Tove Knutsen In March 2021, the Tove Knutsen million, respectively, for loss of hire proceeds which were recorded as a component of total revenues since day rates are recovered under the terms of the policy. In addition, for the three and six months ended June 30, 2021, the Partnership recorded $0.3 million and $0.5 million respectively, for recoveries up to the amount of loss under hull and machinery insurance for repairs to controllable pitch propeller on the Tove Knutsen. million which is classified under vessel operating expense. Bodil Knutsen In April 2021, the Bodil Knutsen

Other Finance Expenses

Other Finance Expenses	6 Months Ended
	Jun. 30, 2021
Other Finance Expenses
Other Finance Expenses	6) Other Finance Expenses (a) Interest Expense The following table presents the components of interest cost as reported in the consolidated statements of operations for the three and six months ended June 30, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, (U.S. Dollars in thousands) 2021 2020 2021 2020 Interest expense ​ $ 6,148 ​ $ 7,886 ​ $ 12,418 ​ $ 17,712 Amortization of debt issuance cost and fair value of debt assumed ​ 656 ​ 626 ​ 1,758 ​ 1,262 Total interest cost ​ $ 6,804 ​ $ 8,512 ​ $ 14,176 ​ $ 18,974 ​ (b) Other Finance Expense The following table presents the components of other finance expense for three and six months ended June 30, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, (U.S. Dollars in thousands) 2021 2020 2021 2020 Bank fees, charges ​ $ 132 ​ $ 137 ​ $ 215 ​ $ 184 Commitment fees ​ 118 62 ​ 194 ​ 123 Total other finance expense ​ $ 250 $ 199 ​ $ 409 ​ $ 307 ​

Derivative Instruments

Derivative Instruments	6 Months Ended
	Jun. 30, 2021
Derivative Instruments
Derivative Instruments	7) Derivative Instruments The unaudited condensed consolidated interim financial statements include the results of interest rate swap contracts to manage the Partnership’s exposure related to changes in interest rates on its variable rate debt instruments and the results of foreign exchange forward contracts to manage its exposure related to changes in currency exchange rates on its operating expenses, mainly crew expenses, in currency other than the U.S. Dollar and on its contract obligations. The Partnership does not apply hedge accounting for derivative instruments. The Partnership does not speculate using derivative instruments. By using derivative financial instruments to economically hedge exposures to changes in interest rates, the Partnership exposes itself to credit risk and market risk. Derivative instruments that economically hedge exposures are used for risk management purposes, but these instruments are not designated as hedges for accounting purposes. Credit risk is the failure of the counterparty to perform under the terms of the derivative instrument. When the fair value of a derivative instrument is positive, the counterparty owes the Partnership, which creates credit risk for the Partnership. When the fair value of a derivative instrument is negative, the Partnership owes the counterparty, and, therefore, the Partnership is not exposed to the counterparty’s credit risk in those circumstances. The Partnership minimizes counterparty credit risk in derivative instruments by entering into transactions with major banking and financial institutions. The derivative instruments entered into by the Partnership do not contain credit risk-related contingent features. The Partnership has not entered into master netting agreements with the counterparties to its derivative financial instrument contracts. Market risk is the adverse effect on the value of a derivative instrument that results from a change in interest rates, currency exchange rates or commodity prices. The market risk associated with interest rate contracts is managed by establishing and monitoring parameters that limit the types and degree of market risk that may be undertaken. The Partnership assesses interest rate risk by monitoring changes in interest rate exposures that may adversely impact expected future cash flows and by evaluating economical hedging opportunities. The Partnership has historically used variable interest rate mortgage debt to finance its vessels. The variable interest rate mortgage debt obligations expose the Partnership to variability in interest payments due to changes in interest rates. The Partnership believes that it is prudent to limit the variability of a portion of its interest payments. To meet this objective, the Partnership has entered into London Interbank Offered Rate (“LIBOR”)-based interest rate swap contracts to manage fluctuations in cash flows resulting from changes in the benchmark interest rate of LIBOR. These swaps change the variable rate cash flow exposure on the mortgage debt obligations to fixed cash flows. Under the terms of the interest rate swap contracts, the Partnership receives LIBOR-based variable interest rate payments and makes fixed interest rate payments, thereby creating the equivalent of fixed rate debt for the notional amount of its debt hedged. As of June 30, 2021 and December 31, 2020, the total notional amount of the Partnership’s outstanding interest rate swap contracts that were entered into in order to hedge outstanding or forecasted debt obligations were $472.6 million and $516.2 million, respectively. As of June 30, 2021 and December 31, 2020, the carrying amount of the interest rate swaps contracts was a net liability of $18.3 million and $30.1 million, respectively. See Note 8—Fair Value Measurements. Changes in the fair value of interest rate swap contracts are reported in realized and unrealized gain (loss) on derivative instruments in the same period in which the related interest affects earnings. The Partnership and its subsidiaries utilize the U.S. Dollar as their functional and reporting currency, because all of their revenues and the majority of their expenditures, including the majority of their investments in vessels and their financing transactions, are denominated in U.S. Dollars. Payment obligations in currencies other than the U.S. Dollar, and in particular operating expenses in NOK, expose the Partnership to variability in currency exchange rates. The Partnership believes that it is prudent to limit the variability of a portion of its currency exchange exposure. To meet this objective, the Partnership entered into foreign exchange forward contracts to manage fluctuations in cash flows resulting from changes in the exchange rates towards the U.S. Dollar. The agreements change the variable exchange rate to fixed exchange rates at agreed dates The following table presents the realized and unrealized gains and losses that are recognized in earnings as net gain (loss) on derivative instruments for the three and six months ended June 30, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, (U.S. Dollars in thousands) 2021 2020 2021 2020 Realized gain (loss): ​ ​ ​ ​ ​ Interest rate swap contracts ​ $ (2,087) ​ $ (191) ​ $ (5,996) ​ $ 12 Foreign exchange forward contracts ​ — ​ (109) ​ — ​ (109) Total realized gain (loss): ​ (2,087) ​ (300) ​ (5,996) ​ (97) Unrealized gain (loss): ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ (178) ​ (3,457) ​ 11,742 ​ (26,438) Foreign exchange forward contracts ​ — ​ 665 ​ — ​ (247) Total unrealized gain (loss): ​ (178) ​ (2,792) ​ 11,742 ​ (26,685) Total realized and unrealized gain (loss) on derivative instruments: ​ $ (2,265) ​ $ (3,092) ​ $ 5,746 ​ $ (26,782) ​

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2021
Fair Value Measurements
Fair Value Measurements	8) Fair Value Measurements (a) Fair Value of Financial Instruments The following table presents the carrying amounts and estimated fair values of the Partnership’s assets and liabilities that are measured at fair value on a recurring and non-recurring basis as of June 30, 2021 and December 31, 2020. Fair value is defined as the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ December 31, 2020 ​ Carrying Fair Carrying Fair (U.S. Dollars in thousands) Amount Value Amount Value Recurring: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Financial assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 51,589 ​ $ 51,589 ​ $ 52,583 ​ $ 52,583 Non-current derivative assets: ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 168 ​ 168 ​ — ​ — Financial liabilities: ​ ​ ​ ​ ​ ​ ​ ​ Current derivative liabilities: ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 9,984 ​ 9,984 ​ 10,695 ​ 10,695 Non-current derivative liabilities: ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 8,495 ​ 8,495 ​ 19,358 ​ 19,358 Long-term debt, current and non-current ​ 1,003,211 ​ 1,003,211 ​ 1,036,118 ​ 1,036,118 Non-Recurring: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Non-current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vessel ​ ​ 48,156 ​ ​ 48,156 ​ ​ — ​ ​ — ​ The carrying amounts shown in the table above are included in the consolidated balance sheets under the indicated captions. Carrying amount of long-term debt, current and non-current, above excludes capitalized debt issuance cost of $5.5 million and $5.8 million as of June 30, 2021 and December 31, 2020 , respectively. The carrying value of trade accounts receivable, trade accounts payable and receivables/payables to owners and affiliates approximate their fair value. The fair values of the financial instruments shown in the above table as of June 30, 2021 and December 31, 2020 represent the amounts that would be received to sell those assets or that would be paid to transfer those liabilities in an orderly transaction between market participants at that date. Those fair value measurements maximize the use of observable inputs. However, in situations where there is little, if any, market activity for the asset or liability at the measurement date, the fair value measurement reflects the Partnership’s own judgment about the assumptions that market participants would use in pricing the asset or liability. Those judgments are developed by the Partnership based on the best information available in the circumstances, including expected cash flows, appropriately risk-adjusted discount rates and available observable and unobservable inputs. The following methods and assumptions were used to estimate the fair value of each class of financial instruments: ● Cash and cash equivalents and restricted cash : The fair value of the Partnership’s cash balances approximates the carrying amounts due to the current nature of the amounts. As of June 30, 2021 and December 31, 2020 there is no restricted cash. ● Interest rate swap contracts : The fair value of interest rate swap contracts is determined using an income approach using the following significant inputs: (1) the term of the swap contract (weighted average of 3.8 years and 4.3 years, as of June 30, 2021 and December 31, 2020 , respectively), (2) the notional amount of the swap contract (ranging from $6.2 million to $38.8 million as of June 30,2021 and ranging from $7.0 million to $40.1 million as of December 31, 2020), discount rates interpolated based on relevant LIBOR swap curves; and (3) the rate on the fixed leg of the swap contract (rates ranging from 0.71% to 2.90% as of June 30, 2021 and from 0.71% to 2.90% as of December 31, 2020). ● Long-term debt : With respect to long-term debt measurements, the Partnership uses market interest rates and adjusts for risks, such as its own credit risk. In determining an appropriate spread to reflect its credit standing, the Partnership considered interest rates currently offered to KNOT for similar debt instruments of comparable maturities by KNOT’s and the Partnership’s bankers as well as other banks that regularly compete to provide financing to the Partnership. ● Vessel : In estimating fair value the Partnership considers factors related to vessel age, expected residual value, ongoing use of the vessels and equipment, shifts in market conditions and other impacting factors associated with the global oil and maritime transportation industries. This exercise in the second quarter of 2021 resulted in a write-down in respect of the Windsor Knutsen using a discounted cash flow approach. The Partnership determined the discounted cash flows for the Windsor Knutsen using projected future redeployment opportunities and estimated residual value, discounted at an estimated market participant rate of 6.38% . The projected future redeployment opportunities take into consideration the Partnership’s projected time-charter rates that could be contracted in future periods. In establishing these estimates, the Partnership considered the specific attributes of this Vessel, current and future potential discussions with potential customers, and available redeployment opportunities. (b) Fair Value Hierarchy The following table presents the placement in the fair value hierarchy of assets and liabilities that are measured at fair value on a recurring basis (including items that are required to be measured at fair value or for which fair value is required to be disclosed) as of June 30, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements ​ ​ ​ ​ at Reporting Date Using ​ ​ ​ ​ ​ Quoted Price ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ in Active ​ Significant ​ ​ ​ ​ ​ Carrying ​ Markets for ​ Other ​ Significant ​ ​ Value ​ Identical ​ Observable ​ Unobservable ​ ​ June 30, ​ Assets ​ Inputs ​ Inputs (U.S. Dollars in thousands) 2021 (Level 1) (Level 2) (Level 3) Recurring: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Financial assets: ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 51,589 ​ $ 51,589 ​ $ — ​ $ — Current derivative assets: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 168 ​ — ​ 168 ​ — Financial liabilities: ​ ​ ​ ​ ​ ​ ​ Non-current derivative liabilities: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 9,984 ​ — ​ 9,984 ​ — Non-current derivative liabilities: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 8,495 ​ — ​ 8,495 ​ — Long-term debt, current and non-current ​ 1,003,211 ​ — ​ 1,003,211 ​ — Non-Recurring: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Non-current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vessel ​ ​ 48,156 ​ ​ — ​ ​ — ​ ​ 48,156 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements ​ ​ ​ ​ at Reporting Date Using ​ ​ ​ ​ ​ Quoted Price ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ in Active ​ Significant ​ ​ ​ ​ ​ Carrying ​ Markets for ​ Other ​ Significant ​ ​ Value ​ Identical ​ Observable ​ Unobservable ​ ​ December 31, ​ Assets ​ Inputs ​ Inputs (U.S. Dollars in thousands) 2020 (Level 1) (Level 2) (Level 3) Financial assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 52,583 ​ $ 52,583 ​ $ — ​ $ — Current derivative assets: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ — ​ — ​ — ​ — Foreign exchange forward contracts ​ — ​ — ​ — ​ — Non-current derivative assets: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ — ​ — ​ — ​ — Financial liabilities: ​ ​ ​ ​ ​ ​ ​ Current derivative liabilities: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 10,695 ​ — ​ 10,695 ​ — Non-current derivative liabilities: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 19,358 ​ — ​ 19,358 ​ — Long-term debt, current and non-current ​ 1,036,118 ​ — ​ 1,036,118 ​ — ​ The Partnership’s accounting policy is to recognize transfers between levels of the fair value hierarchy on the date of the event or change in circumstances that caused the transfer. There were no transfers into or out of Level 1 and Level 2 as of June 30, 2021 and December 31, 2020 . As of June 30, 2021, one non-recurring asset was recognized as Level 3. The following table provide information about the valuation techniques and significant unobservable inputs used in the valuation of Level 3 assets measured at fair value on a non-recurring basis as of June 30, 2021. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Significant ​ ​ ​ Fair ​ ​ ​ unobservable ​ ​ (U.S. Dollars in thousands) ​ Value ​ Valuation technique ​ inputs: ​ WACC (1) Non-Recurring: ​ ​ Non-current assets: ​ ​ Windsor Knutsen ​ $ 48,156 Discounted cash flow Discount rate 6.38 % ​ (1) WACC is defined as weighted average cost of capital

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2021
Income Taxes
Income Taxes	9) Income Taxes Components of Current and Deferred Tax Expense After the reorganization of the Partnership’s predecessor’s activities into the new group structure in February 2013, all profit from continuing operations in Norway is taxable within the tonnage tax regime. The consequence of the reorganization is a one-time entrance tax into the Norwegian tonnage tax regime due to the Partnership’s acquisition of the shares in the subsidiary that owns the Fortaleza Knutsen Recife Knutsen The total amount of the entrance tax was estimated to be $3.0 million, which was recognized in the three months ended March 31, 2013. At September 30, 2017 the Partnership acquired the shares in the subsidiary that owns the Lena Knutsen The taxes payable, mainly related to the entrance tax, are calculated based on the Norwegian corporate tax rate of 22% for 2021 and 2020, and the deferred tax liabilities, also mainly related to the entrance tax, are calculated based on a tax rate of 22% effective as from January 1, 2021 and January 1, 2020, respectively. $0.1 million of the entrance tax was paid both during the first quarter of 2021 and 2020. As of June 30, 2021 and December 31, 2020, UK income tax is presented as income taxes payable, while $0.3 million and $0.3 million is presented as non-current deferred taxes payable, respectively. Significant components of current and deferred income tax expense attributable to income from continuing operations for the three and six months ended June 30, 2021 and 2020 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ (U.S. Dollars in thousands) 2021 2020 2021 2020 Income before income taxes ​ $ (10,664) ​ $ 21,686 ​ $ 17,480 ​ $ 15,550 ​ Income tax (expense) ​ ​ (261) ​ ​ (3) ​ ​ (264) ​ ​ (6) ​ Effective tax rate ​ $ 2 % $ 0 % $ (2) % $ 0 % ​ Income tax expenses for the three and six months ended June 30, 2021 and 2020 consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ (U.S. Dollars in thousands) ​ 2021 ​ 2020 ​ 2021 ​ 2020 ​ Income tax benefit (expense) - Norwegian tonnage tax $ (258) $ — $ (258) $ — ​ Income tax benefit (expense) - UK ​ ​ (3) ​ ​ (3) ​ ​ (6) ​ ​ (6) ​ Income tax benefit (expense) $ (261) $ (3) $ (264) $ (6) ​ Effective tax rate ​ ​ 2 % ​ 0 % ​ (2) % ​ 0 % ​ The Partnership records a valuation allowance for deferred tax assets when it is more likely than not that some of or all of the benefit from the deferred tax assets will not be realized. In assessing the realizability of deferred tax assets, which relates to financial loss carry forwards and other deferred tax assets within the tonnage tax regime, the Partnership considers whether it is more-likely-than-not that some portion or all of the deferred tax assets will not be realized taking into account all the positive and negative evidence available. As of June 30, 2021 and December 31, 2020 there are no deferred tax assets recognized.

Vessels and Equipment

Vessels and Equipment	6 Months Ended
	Jun. 30, 2021
Vessels and Equipment
Vessels and Equipment	10) Vessels and Equipment As of June 30, 2021 and December 2020, Vessels with a book value of $1,642 million and $1,709 million, respectively, are pledged as security held as a guarantee for the Partnership’s long-term debt. See Note 12—Long-term debt. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vessels & ​ Accumulated ​ ​ Accumulated write ​ ​ ​ (U.S. Dollars in thousands) equipment ​ depreciation ​ down ​ Net Vessels Vessels, December 31, 2019 ​ $ 2,129,012 $ (451,524) $ — $ 1,677,488 Additions ​ 115,277 ​ — ​ ​ — ​ 115,277 Drydock costs ​ 5,764 ​ — ​ ​ — ​ 5,764 Disposals ​ — ​ — ​ ​ — ​ — Depreciation for the year ​ — ​ (89,743) ​ ​ — ​ (89,743) Vessels, December 31, 2020 ​ $ 2,250,053 ​ $ (541,267) ​ $ — ​ $ 1,708,786 Additions (1) ​ 6,748 ​ — ​ ​ — ​ 6,748 Drydock costs ​ 3,428 ​ — ​ ​ — ​ 3,428 Disposals ​ (2,641) ​ 2,641 ​ ​ — ​ — Depreciation and write down for the period (2) ​ — ​ (47,515) ​ ​ (29,421) ​ (76,936) Vessels, June 30, 2021 ​ $ 2,257,588 ​ $ (586,141) ​ $ (29,421) ​ $ 1,642,026 ​ (1) During the scheduled second renewal survey drydocking of the Bodil Knutsen a ballast water treatment system was installed on the vessel. ​ (2) The carrying value of the Windsor Knutsen was written down to its estimated fair value as of June 30, 2021, see Note 19 - Write-down of long-lived assets. ​ Drydocking activity for the year ended June 30, 2021 and December 31, 2020 is summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ (U.S. Dollars in thousands) At June 30, 2021 At December 31, 2020 Balance at the beginning of the year ​ $ 17,106 ​ $ 18,523 Costs incurred for dry docking ​ 3,428 ​ 2,724 Costs allocated to drydocking as part of acquisition of asset ​ — ​ 3,040 Drydock amortization ​ (3,948) ​ (7,181) Balance at the end of the year ​ $ 16,586 ​ $ 17,106 ​

Intangible Assets

Intangible Assets	6 Months Ended
	Jun. 30, 2021
Intangible Assets
Intangible Assets	11) Intangible Assets and Contract Liabilities (a) Intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Above market ​ Above market ​ ​ ​ ​ time charter time charter Total (U.S. Dollars in thousands) ​ Tordis Knutsen ​ Vigdis Knutsen ​ intangibles Intangibles, December 31, 2019 ​ $ 608 ​ $ 678 ​ $ 1,286 Amortization for the year ​ (303) ​ (302) ​ (605) Intangibles, December 31, 2020 ​ $ 305 ​ $ 376 ​ $ 681 Amortization for the period ​ (152) ​ (151) ​ (303) Intangibles, June 30, 2021 ​ $ 153 ​ $ 225 ​ $ 378 ​ The intangible for the above-market value of the time charter contract associated with the Tordis Knutsen Vigdis Knutsen ​ The estimated future amortization of intangible assets at June 30, 2021 is as follows: ​ ​ ​ ​ ​ (U.S. Dollars in thousands) ​ Remainder of 2021 ​ 303 2022 ​ 75 Total ​ $ 378 ​ (b) Contract Liabilities The unfavorable contractual rights for charters associated with Fortaleza Knutsen Recife Knutsen Fortaleza Knutsen Recife Knutsen Fortaleza Knutsen Recife Knutsen ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortization for ​ Amortization for ​ ​ ​ Balance of ​ the year ended ​ Balance of ​ the six Months ​ Balance of ​ ​ December 31, ​ December 31, ​ December 31, ​ ended June 30, ​ June 30, (U.S. Dollars in thousands) ​ 2019 ​ 2020 ​ 2020 ​ 2021 ​ 2021 Contract liabilities: ​ ​ ​ ​ ​ Unfavourable contract rights ​ $ (5,203) ​ $ 1,517 ​ $ (3,686) ​ $ 758 ​ $ (2,928) Total amortization income ​ ​ $ 1,517 ​ ​ $ 758 ​ ​ Accumulated amortization for contract liabilities was $15.3 million and $14.5 million as of June 30, 2021 and December 31, 2020, respectively. The amortization of contract liabilities that is classified under time charter and bareboat revenues for the next five years is expected to be as follows: ​ ​ ​ ​ ​ (U.S. Dollars in thousands) ​ Remainder of 2021 ​ 759 2022 ​ 1,518 2023 ​ 651 2024 ​ — 2025 ​ — 2026 ​ — Total ​ $ 2,928 ​

Long-Term Debt

Long-Term Debt	6 Months Ended
	Jun. 30, 2021
Long-Term Debt
Long-Term Debt	12) Long-Term Debt As of June 30, 2021 and December 31, 2020, the Partnership had the following debt amounts outstanding: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, (U.S. Dollars in thousands) Vessel 2021 2020 $320 million loan facility ​ Windsor Knutsen, Bodil Knutsen, Carmen Knutsen, Fortaleza Knutsen, Recife Knutsen, Ingrid Knutsen ​ $ 237,190 ​ $ 252,245 $55 million revolving credit facility ​ ​ ​ 5,000 ​ 34,279 Hilda loan facility Hilda Knutsen ​ 75,385 ​ 78,462 Torill loan facility Torill Knutsen ​ 78,333 ​ 81,667 $172.5 million loan facility Dan Cisne, Dan Sabia ​ 52,140 ​ 58,340 Raquel loan facility Raquel Knutsen ​ — ​ 52,725 Tordis loan facility Tordis Knutsen ​ 73,341 ​ 75,871 Vigdis loan facility Vigdis Knutsen ​ 74,606 ​ 77,136 Lena loan facility Lena Knutsen ​ 73,500 ​ 75,950 Brasil loan facility Brasil Knutsen ​ 47,855 ​ 50,997 Anna loan facility Anna Knutsen ​ 60,157 ​ 62,196 Tove loan facility ​ Tove Knutsen ​ ​ 84,066 ​ ​ 86,250 $25 million revolving credit facility with NTT ​ 25,000 ​ 25,000 $25 million revolving credit facility with Shinsei ​ ​ ​ ​ 25,000 ​ ​ 25,000 Raquel Sale & Leaseback ​ Raquel Knutsen ​ ​ 91,638 ​ ​ — Total long-term debt ​ $ 1,003,211 ​ $ 1,036,118 Less: current installments ​ 353,643 ​ 186,723 Less: unamortized deferred loan issuance costs ​ 2,273 ​ 2,535 Current portion of long-term debt ​ 351,370 ​ 184,188 Amounts due after one year ​ 649,568 ​ 849,395 Less: unamortized deferred loan issuance costs ​ 3,220 ​ 3,238 Long-term debt, less current installments, and unamortized deferred loan issuance costs ​ $ 646,348 ​ $ 846,157 ​ The Partnership’s outstanding debt of $1,003.2 million as of June 30, 2021 is repayable as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (U.S. Dollars in thousands) ​ Sale & Leaseback Period repayment Balloon repayment Total Remainder of 2021 $ 2,433 ​ $ 43,142 $ 70,811 ​ $ 116,386 2022 ​ 4,960 ​ ​ 70,348 ​ 236,509 ​ ​ 311,817 2023 ​ 5,177 ​ ​ 54,672 ​ 230,906 ​ ​ 290,755 2024 ​ 5,418 ​ ​ 13,011 ​ 123,393 ​ ​ 141,822 2025 ​ 5,640 ​ ​ 3,276 ​ 65,506 ​ ​ 74,422 2026 and thereafter ​ 68,009 ​ ​ — ​ — ​ ​ 68,009 Total ​ $ 91,637 ​ $ 184,449 ​ $ 727,125 ​ $ 1,003,211 ​ As of June 30, 2021, the interest rates on the Partnership’s loan agreements were LIBOR plus a fixed margin ranging from 1.75% to 2.40%. On June 30, 2021, the Partnership’s subsidiary, KNOT Shuttle Tankers AS, which owns all of the Partnership’s vessel-owning entities, extended the maturity of its $25 million unsecured revolving facility with NTT Finance Corporation on unchanged terms. The extended facility matures in August 2023.

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2021
Related Party Transactions
Related Party Transactions	13) Related Party Transactions (a) Related Parties Net income (expense) from related parties included in the unaudited condensed consolidated statements of operations for the three and six months ended June 30, 2021 and 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, (U.S. Dollars in thousands) 2021 2020 2021 ​ 2020 Statements of operations: ​ ​ ​ ​ ​ ​ ​ ​ Time charter and bareboat revenues: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Time charter income from KNOT (1) ​ $ 1,866 ​ $ 105 ​ $ 1,866 ​ $ 4,883 Operating expenses: ​ ​ ​ ​ ​ ​ ​ ​ Vessel operating expenses (2) ​ ​ 5,000 ​ ​ 4,392 ​ ​ 7,752 ​ ​ 6,856 Technical and operational management fee from KNOT to Vessels (3) ​ 2,106 ​ 1,703 ​ 4,214 ​ 3,406 Operating expenses from other related parties (4) ​ ​ 172 ​ ​ 66 ​ ​ 299 ​ ​ 229 General and administrative expenses: ​ ​ ​ ​ ​ ​ ​ ​ Administration fee from KNOT Management (5) ​ 379 ​ 244 ​ 666 ​ 474 Administration fee from KOAS (5) ​ 201 ​ 165 ​ 395 ​ 323 Administration fee from KOAS UK (5) ​ 19 ​ 31 ​ 37 ​ 61 Administration and management fee from KNOT (6) ​ 20 ​ 40 ​ 29 ​ 85 Total income (expenses) ​ $ (6,031) ​ $ (6,536) ​ $ (11,526) ​ $ (6,551) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ At June 30, ​ At December 31, (U.S. Dollars in thousands) 2021 2020 Balance Sheet: ​ ​ Vessels: ​ ​ Drydocking supervision fee from KNOT (7) ​ $ 134 ​ $ 47 Total ​ $ 134 ​ $ 47 (1) Time charter income from KNOT: On December 17, 2018, the Partnership's subsidiary that owns the Windsor Knutsen and Royal Dutch Shell ("Shell") agreed to suspend the vessel's time charter contract. The suspension period commenced March 4, 2019 and ended April 5, 2020, when the vessel was redelivered to Shell. During the suspension period, the Windsor Knutsen operated under a time charter contract with Knutsen Shuttle Tankers Pool AS on the same terms as the existing time charter contract with Shell. After completing its drydock in the second quarter of 2021, the Bodil Knutsen has operated under a time charter with Knutsen Shuttle Tankers Pool AS for an initial three-month period commencing on May 13, 2021 and then on a rolling one-month basis. (2) Vessel operating expenses: KNOT Management or KNOT Management Denmark provides technical and operational management of the vessels on time charter including crewing and crew training services. (3) Technical and operational management fee, from KNOT Management or KNOT Management Denmark to Vessels : KNOT Management or KNOT Management Denmark provides technical and operational management of the vessels on time charter including crewing, purchasing, maintenance and other operational service. In addition, there is also a charge for 24-hour emergency response services provided by KNOT Management for all vessels managed by KNOT Management. (4) Operating expenses from other related parties : Simsea Real Operations AS, a company jointly owned by the Partnership’s Chairman of the Board, Trygve Seglem, and by other third-party shipping companies in Haugesund, provides simulation, operational training assessment and other certified maritime courses for seafarers. The cost is course fees for seafarers. Knutsen OAS Crewing AS, a subsidiary of TSSI, provides administrative services related to East European crew on vessels operating on time charter contracts. The cost is a fixed fee per month per East European crew onboard the vessel. (5) Administration fee from KNOT Management, Knutsen OAS Shipping AS (“KOAS”) and Knutsen OAS (UK) Ltd. (“KOAS UK”) : Administration costs include compensation and benefits of KNOT Management’s management and administrative staff as well as other general and administration expenses. Some benefits are also provided by KOAS and KOAS UK . Net administration costs are total administration cost plus a 5% margin, reduced for the total fees for services delivered by the administration staffs and the estimated shareholder costs for KNOT that have not been allocated. As such, the level of net administration costs as a basis for the allocation can vary from year to year based on the administration and financing services offered by KNOT to all the vessels in its fleet each year. KNOT Management also charges each subsidiary a fixed annual fee for the preparation of the statutory financial statement. (6) Administration and management fee from KNOT Management and KNOT Management Denmark : For bareboat charters, the shipowner is not responsible for providing crewing or other operational services and the customer is responsible for all vessel operating expenses and voyage expenses. However, each of the vessels under bareboat charters is subject to a management and administration agreement with either KNOT Management or KNOT Management Denmark, pursuant to which these companies provide general monitoring services for the vessels in exchange for an annual fee. (7) Drydocking supervision fee from KNOT and KOAS : KNOT and KOAS provide supervision and hire out service personnel during drydocking of the vessels. The fee is calculated as a daily fixed fee. (b) Transactions with Management and Directors See the footnotes to Note 13(a)—Related Party Transactions for a discussion of transactions with management and directors included in the consolidated statements of operations. (c) Amounts Due from (to) Related Parties Balances with related parties consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ At June 30, ​ At December 31, (U.S. Dollars in thousands) 2021 2020 Balance Sheet: ​ ​ Trading balances due from KOAS ​ $ 55 ​ $ 170 Trading balances due from KNOT and affiliates (1) ​ 1,707 ​ 5,556 Amount due from related parties ​ $ 1,762 ​ $ 5,726 Trading balances due to KOAS ​ $ 2,489 ​ $ 1,596 Trading balances due to KNOT and affiliates ​ 961 ​ 544 Amount due to related parties ​ $ 3,450 ​ $ 2,140 ​ (1) On December 31, 2020, the Partnership's wholly owned subsidiary, KNOT Shuttle Tankers AS, acquired KNOT's 100% interest in KNOT Shuttle Tankers 34 AS ("KNOT 34"), the company that owns and operates the Tove Knutsen Trading balances due from KNOT and affiliates as of December 31, 2020 includes the post-closing settlement amount of $3.6 million related to the acquisition of the Tove Knutsen. ​ Amounts due from (to) related parties are unsecured and intended to be settled in the ordinary course of business. The majority of these related party transactions relate to vessel management and other fees due to KNOT, KNOT Management, KOAS UK and KOAS. (d) Trade accounts payable Trade accounts payable to related parties are included in total trade accounts payable in the balance sheet. The balances to related parties consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ At June 30, ​ At December 31, (U.S. Dollars in thousands) 2021 2020 Balance Sheet: ​ ​ ​ ​ Trading balances due to KOAS ​ $ 920 ​ $ 1,304 Trading balances due to KNOT and affiliates ​ 522 ​ 902 Trade accounts payables to related parties ​ $ 1,442 ​ $ 2,206 ​ Trading balances from KNOT and affiliates are included in other current assets in the balance sheet. The balances from related parties consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ At June 30, At December 31, (U.S. Dollars in thousands) ​ 2021 ​ 2020 Balance Sheet: ​ ​ Trading balances due from KNOT and affiliates $ 893 ​ $ 1,697 Trading balances due from KOAS ​ 353 ​ 450 Other current assets from related parties ​ $ 1,246 ​ $ 2,147 ​

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies
Commitments and Contingencies	14) Commitments and Contingencies Assets Pledged As of June 30, 2021 and December 31, 2020, Vessels with a book value of $1,642 million and $1,709 million, respectively, were pledged as security held as guarantee for the Partnership’s long-term debt and interest rate swap obligations. See Note 7—Derivative Instruments, Note 10 - Vessels and Equipment and Note 12—Long-Term Debt. Claims and Legal Proceedings Under the Partnership's time charters, claims to reduce the hire rate payments can be made if the Vessel does not perform to certain specifications in the agreements. No accrual for possible claim was recorded for the period ended June 30, 2021 and the year ended December 31, 2020. From time to time, the Partnership is involved in various claims and legal actions arising in the ordinary course of business. In the opinion of management, the ultimate disposition of these matters will not have a material adverse effect on the consolidated financial position, results of operations or cash flows. Insurance The Partnership maintains insurance on all the Vessels to insure against marine and war risks, which include damage to or total loss of the Vessels, subject to deductible amounts that average $0.15 million per Vessel, and loss of hire. Under the loss of hire policies, the insurer will pay a compensation for the lost hire rate agreed in respect of each Vessel for each day, in excess of 14 deductible days, for the time that the Vessel is out of service as a result of damage, for a maximum of 180 days. In addition, the Partnership maintains protection and indemnity insurance, which covers third-party legal liabilities arising in connection with the Vessels’ activities, including, among other things, the injury or death of third-party persons, loss or damage to cargo, claims arising from collisions with other vessels and other damage to other third-party property, including pollution arising from oil or other substances. This insurance is unlimited, except for pollution, which is limited to $1 billion per vessel per incident. The protection and indemnity insurance is maintained through a protection and indemnity association, and as a member of the association, the Partnership may be required to pay amounts above budgeted premiums if the member claims exceed association reserves, subject to certain reinsured amounts. If the Partnership experiences multiple claims each with individual deductibles, losses due to risks that are not insured or claims for insured risks that are not paid, it could have a material adverse effect on the Partnership’s results of operations and financial condition. Windsor Knutsen In December 2020, the Windsor Knutsen million, respectively, for loss of hire proceeds which were recorded as a component of total revenues since day rates are recovered under the terms of the policy. In addition, for the three and six months ended June 30, 2021, the Partnership recorded $2.5 million and $4.1 million, respectively, for recoveries up to the amount of loss under hull and machinery insurance for repairs as a result of the engine block damage to the Windsor Knutsen. Tove Knutsen In March 2021, the Tove Knutsen million, respectively, for loss of hire proceeds which were recorded as a component of total revenues since day rates are recovered under the terms of the policy. In addition, for the three and six months ended June 30, 2021, the Partnership recorded $0.3 million and $0.5 million respectively, for recoveries up to the amount of loss under hull and machinery insurance for repairs as a result of the leakage from the controllable pitch propeller to the Tove Knutsen. Bodil Knutsen In April 2021, the Bodil Knutsen

Earnings per Unit and Cash Dist

Earnings per Unit and Cash Distributions	6 Months Ended
	Jun. 30, 2021
Earnings per Unit and Cash Distributions
Earnings per Unit and Cash Distributions	15) Earnings per Unit and Cash Distributions The calculations of basic and diluted earnings per unit (1) are presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, (U.S. Dollars in thousands, except per unit data) 2021 2020 2021 2020 Net income (loss) ​ $ (10,925) ​ $ 21,683 ​ $ 17,216 ​ $ 15,544 Less: Series A Preferred unitholders’ interest in net income ​ ​ 1,759 ​ ​ 1,800 ​ ​ 3,559 ​ ​ 3,600 Net income attributable to the unitholders of KNOT Offshore Partners LP ​ ​ (12,684) ​ ​ 19,883 ​ ​ 13,657 ​ ​ 11,944 Less: Distributions (2) ​ ​ 18,150 ​ ​ 18,034 ​ ​ 36,184 ​ ​ 36,068 Under (over) distributed earnings ​ ​ (30,834) ​ ​ 1,849 ​ ​ (22,527) ​ ​ (24,124) Under (over) distributed earnings attributable to: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common unitholders (3) ​ ​ (30,268) ​ ​ 1,815 ​ ​ (22,114) ​ ​ (23,679) General Partner ​ ​ (566) ​ ​ 34 ​ ​ (413) ​ ​ (445) Weighted average units outstanding (basic) (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Common unitholders ​ ​ 32,782 ​ ​ 32,694 ​ ​ 32,738 ​ ​ 32,694 General Partner ​ ​ 615 ​ ​ 615 ​ ​ 615 ​ ​ 615 Weighted average units outstanding (diluted) (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common unitholders (4) ​ ​ 36,619 ​ ​ 36,596 ​ ​ 36,594 ​ ​ 36,648 General Partner ​ ​ 615 ​ ​ 615 ​ ​ 615 ​ ​ 615 Earnings per unit (basic) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common unitholders ​ $ (0.38) ​ $ 0.60 ​ $ 0.41 ​ $ 0.36 General Partner ​ ​ (0.38) ​ ​ 0.60 ​ ​ 0.41 ​ ​ 0.36 Earnings per unit (diluted): ​ ​ ​ ​ ​ ​ ​ ​ ​ Common unitholders (4) ​ $ (0.38) ​ $ 0.58 ​ $ 0.41 ​ $ 0.36 General Partner ​ ​ (0.38) ​ ​ 0.60 ​ ​ 0.41 ​ ​ 0.36 Cash distributions declared and paid in the period per unit (5) ​ ​ 0.52 ​ ​ 0.52 ​ ​ 1.04 ​ ​ 1.04 Subsequent event: Cash distributions declared and paid per unit relating to the period (6) ​ ​ 0.52 ​ ​ 0.52 ​ ​ 1.04 ​ ​ 1.04 (1) Earnings per unit have been calculated in accordance with the cash distribution provisions set forth in the Partnership Agreement. (2) This refers to distributions made or to be made in relation to the period irrespective of the declaration and payment dates and based on the number of units outstanding at the record date. This includes cash distributions to the IDR holder (KNOT) for the three months ended June 30, 2021 and 2020 of $0.7 million and for the six months ended June 30, 2021 and 2020 of $1.4 million. (3) This includes the net income attributable to the IDR holder. The net income attributable to IDRs for the three months ended June 30, 2021 and 2020 was $0.7 million and for the six months ended June 30, 2021 and 2020 was $1.4 . (4) Diluted weighted average units outstanding and earnings per unit diluted for the three and six months ended June 30, 2021 and 2020 does not reflect any potential common shares relating to the convertible preferred units since the assumed issuance of any additional shares would be anti-dilutive. (5) Refers to cash distributions declared and paid during the period. (6) Refers to cash distributions declared and paid subsequent to the period end. On May 27, 2021, Tortoise Direct Opportunities Fund LP, the holder of 416,677 of the Partnership’s Series A Convertible Preferred Units, sold 208,333 of its Series A Preferred Units to KNOT and converted 208,334 Series A Preferred Units to 215,292 common units based on a conversion rate of 1.0334. As of June 30, 2021, 73.7% of the Partnership’s total number of common units outstanding representing limited partner interests were held by the public (in the form of 24,251,518 common units) and 26.0% of such units were held directly by KNOT (in the form of 8,567,500 common units). In addition, KNOT, through its ownership of the General Partner, held a 1.83% general partner interest (in the form of 615,117 general partner units) and a 0.3% limited partner interest (in the form of 90,368 common units). KNOT also holds 208,333 Series A Preferred Units. Earnings per unit – basic is determined by dividing net income, after deducting the amount of net income attributable to the Series A Preferred Units and the distribution paid or to be made in relation to the period, by the weighted-average number of units outstanding during the applicable period. The computation of limited partners’ interest in net income per common unit – diluted assumes the issuance of common units for all potentially dilutive securities consisting of 3,541,666 Series A Preferred Units. Consequently, the net income attributable to limited partners’ interest is exclusive of any distributions on the Series A Preferred Units. In addition, the weighted average number of common units outstanding has been increased assuming the Series A Preferred Units have been converted to common units using the if-converted method. The computation of limited partners’ interest in net income per common unit – diluted does not assume the issuance of Series A Preferred Units if the effect would be anti-dilutive. The General Partner’s and common unitholders’ interest in net income was calculated as if all net income was distributed according to the terms of the Partnership Agreement, regardless of whether those earnings would or could be distributed. The Partnership Agreement does not provide for the distribution of net income. Rather, it provides for the distribution of available cash, which is a contractually defined term that generally means all cash on hand at the end of each quarter less the amount of cash reserves established by the Board to provide for the proper conduct of the Partnership’s business, including reserves for maintenance and replacement capital expenditures, anticipated credit needs and capital requirements and any accumulated distributions on, or redemptions of, the Series A Preferred Units. In addition, KNOT, as the initial holder of all IDRs, has the right, at the time when it has received incentive distributions at the highest level to which it is entitled (48.0% for each of the prior four consecutive fiscal quarters), to reset the initial cash target distribution levels at higher levels based on the distribution at the time of the exercise of the reset election. Unlike available cash, net income is affected by non-cash items, such as depreciation and amortization, unrealized gains and losses on derivative instruments and unrealized foreign currency gains and losses.

Acquisitions

Acquisitions	6 Months Ended
	Jun. 30, 2021
Acquisitions
Acquisitions	16) Acquisitions In December 2020, the Partnership acquired from KNOT equity interests in the subsidiary which owns and operates the Tove Knutsen. The Board and the Conflicts Committee approved the purchase price for the transaction. The Conflicts Committee retained a financial advisor to assist with its evaluation of the transaction. The detail of the transaction are as follows: ​ ​ ​ ​ ​ ​ Final ​ ​ Tove Knutsen ​ ​ December 31, (U.S. Dollars in thousands) ​ 2020 Purchase consideration (1) ​ $ 21,898 Less: Fair value of net assets acquired: ​ Vessels and equipment (2) ​ 117,978 Intangibles: Above market time charter ​ — Cash ​ 804 Inventories ​ 136 Derivatives assets (liabilities) ​ (3,537) Others current assets ​ 270 Amounts due from related parties ​ — Long-term debt ​ (93,139) Long-term debt from related parties ​ — Deferred debt issuane ​ 769 Trade accounts payable ​ (430) Accrued expenses ​ (622) Amounts due to related parties ​ ​ (331) Subtotal ​ ​ 21,898 Difference between the purchase price and fair value of net assets acquired ​ $ — (1) The purchase consideration comprises the following: ​ ​ ​ ​ ​ ​ Final ​ ​ ToveKnutsen ​ ​ December 31, (U.S. Dollars in thousands) ​ 2020 Cash consideration paid to KNOT (from KNOP) ​ $ 25,430 Purchase price adjustments ​ (3,596) Acquisition-related costs ​ 64 Purchase price ​ $ 21,898 (2) Vessel and Equipment includes allocations to dry docking (in thousands) of $3,040 . ​

Unit Activity

Unit Activity	6 Months Ended
	Jun. 30, 2021
Unit Activity
Unit Activity	17) Unit Activity The following table shows the movement in number of common units, general partner units and Series A Preferred Units from December 31, 2020 until June 30, 2021. ​ ​ ​ ​ ​ ​ ​ (in units) Common Units General Partner Units Convertible Preferred Units December 31, 2020 32,694,094 615,117 3,750,000 May 27, 2021: Conversion of Series A Preferred Units 215,292 — (208,334) June 30, 2021 32,909,386 615,117 3,541,666 ​ On May 27, 2021 Tortoise Direct Opportunities Fund LP, the holder of 416,677 of the Partnership’s Series A Convertible Preferred Units sold 208,333 of its Series A Preferred Units to KNOT and converted 208,334 Series A Preferred Units to 215,292 common units based on with a Series A conversion rate of 1.0334.

Trade Accounts Receivable and O

Trade Accounts Receivable and Other Current Assets	6 Months Ended
	Jun. 30, 2021
Trade Accounts Receivable and Other Current Assets
Trade Accounts Receivable and Other Current Assets	18) Trade Accounts Receivable and Other Current Assets (a) Trade Accounts Receivable Trade accounts receivables are presented net of provisions for expected credit loss. As of June 30, 2021 and December 31, 2020, there were no provision for expected credit loss. (b) Other Current Assets The following table presents other currents assets of June 30, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ (U.S. Dollars in thousands) At June 30, 2021 At December 31, 2020 Insurance claims for recoveries ​ 7,477 ​ — Refund of value added tax ​ 1,762 ​ 1,429 Prepaid expenses ​ 1,392 ​ 1,050 Other receivables ​ 3,750 ​ 3,032 Total other current assets ​ $ 14,381 ​ $ 5,511 ​

Write-Down of Long-Lived Assets

Write-Down of Long-Lived Assets	6 Months Ended
	Jun. 30, 2021
Write-Down of Long-Lived Assets
Write-Down of Long-Lived Assets	19) Write-Down of Long-Lived Assets The carrying value of the Partnership’s fleet is regularly assessed as events or changes in circumstances may indicate that a vessel’s net carrying value exceeds the net undiscounted cash flows expected to be generated over its remaining useful life, and in such situation the carrying amount of the vessel is reduced to its estimated fair value. The Partnership considers factors related to vessel age, expected residual value, ongoing use of the vessels and equipment, shifts in market conditions and other impacting factors associated with the global oil and maritime transportation industries. This exercise in the second quarter of 2021 resulted in a write-down in respect of the Windsor Knutsen Windsor Knutsen Windsor Knutsen

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2021
Subsequent Events
Subsequent Events	20) Subsequent Events The Partnership has evaluated subsequent events from the balance sheet date through August 26, 2021, the date at which the unaudited condensed consolidated interim financial statements were available to be issued, and determined that there are no other items to disclose, except as follows: On August 12, 2021, the Partnership paid a quarterly cash distribution of $0.52 per common unit with respect to the quarter ended June 30, 2021 to all common unitholders of record on July 29, 2021. On August 12, 2021, the Partnership paid a cash distribution to holders of Series A Convertible Preferred Units (“Series A Preferred Units”) with respect to the quarter ended June 30, 2021 in an aggregate amount equal to $1.7 million. On August 25, 2021 the Partnership’s subsidiaries that own the Tordis Knutsen Vigdis Knutsen Lena Knutsen Anna Knutsen Brasil Knutsen on the vessels. The senior secured credit facilities will refinance the previously existing term loans related to these vessels which were due to mature between November 2021 and July 2022. Closing of the senior secured credit facility is anticipated to occur in September 2021. On August 26, 2021, the Partnership entered into a sales agreement with B. Riley Securities, Inc. (the “Agent”). Under the terms of the at the market sales agreement, the Partnership may offer and sell up to $100 million of common units under the ATM program (the “ATM program”), from time to time, through the Agent. The Partnership intends to use the net proceeds of any sales of common units for general partnership purposes, which may include, among other things, the repayment of indebtedness or the funding of acquisitions or other capital expenditures. After the balance sheet date, there continues to be significant macroeconomic uncertainty as a result of the Coronavirus (COVID-19) outbreak. The scale and duration of this development remains uncertain and could materially impact the Partnership's earnings and cash flow.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Summary of Significant Accounting Policies
Basis of Preparation	(a) Basis of Preparation The accompanying unaudited condensed consolidated interim financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the U.S. Securities and Exchange Commission (the “SEC”) for interim financial information. In the opinion of management of the Partnership, all adjustments considered necessary for a fair presentation, which are of normal recurring nature, have been included. All intercompany balances and transactions are eliminated. The unaudited condensed consolidated financial statements do not include all the disclosures and information required for a complete set of annual financial statements; and, therefore, these unaudited condensed consolidated financial statements should be read in conjunction with the Partnership’s audited consolidated financial statements for the year ended December 31, 2020, which are included in the Partnership’s Annual Report on Form 20-F (the “2020 20-F”).
Significant Accounting Policies	(b) Significant Accounting Policies The accounting policies adopted in the preparation of the unaudited condensed consolidated interim financial statements are consistent with those followed in the preparation of the Partnership’s audited consolidated financial statements for the year ended December 31, 2020, as contained in the Partnership’s 2020 20-F.
Vessels and Equipment	Vessels and Equipment Historically, the useful life of the Partnership’s vessels and equipment was assessed as 25 years commencing from the date the vessel and equipment were delivered from the shipyard. As of June 30, 2021, the Partnership has considered factors related to the ongoing use of the vessels and equipment, gradual shifts in market conditions and other long-term factors associated with the global oil and maritime transportation industries and based on this has reassessed the useful life as being 23 years. This change in estimate will be applied prospectively from July 1, 2021 and impacts the entire fleet of shuttle tanker vessels. The change in estimate did however not impact income, net income nor earnings per share basic and diluted for the three and six months ended June 30, 2021.
Recent Accounting Pronouncements	(c) Recent Accounting Pronouncements Adoption of new accounting standards No new accounting standards have recently been adopted. Accounting pronouncements not yet adopted In March 2020, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2020-04 Reference Rate Reform (Topic 848), Facilitation of the Effects of Reference Rate Reform on Financial Reporting. The update provides temporary optional expedients and exceptions to the guidance in US GAAP on contract modifications and hedge accounting, to ease the financial reporting burdens related to the expected market transition from the London Interbank Offered Rate (LIBOR) and other interbank offered rates to alternative reference rates. For all types of hedging relationships, the guidance allows an entity to change the reference rate and other critical terms related to reference rate reform without having to dedesignate the relationship. The guidance is effective upon issuance through December 31, 2022. Although the Partnership does not apply hedge accounting, the Partnership has debt and interest rate swaps that reference LIBOR. The Partnership is evaluating the impact of the guidance on the consolidated financial statements. Other recently issued accounting pronouncements are not expected to materially impact the Partnership.

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2021
Segment Information
Schedule consolidated revenues and percentages of revenues for customers	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ (U.S. Dollars in thousands) 2021 2020 2021 2020 ​ Eni Trading and Shipping S.p.A. ​ $ 10,915 16 % $ 10,953 16 % $ 21,748 16 % $ 22,088 16 % Fronape International Company, a subsidiary of Petrobras Transporte S.A. ​ 11,249 17 % 11,249 16 % 22,378 17 % 22,498 16 % Repsol Sinopec Brasil, S.A., a subsidiary of Repsol Sinopec Brasil, B.V. ​ 9,282 14 % 9,285 13 % 18,075 14 % 15,178 11 % Brazil Shipping I Limited, a subsidiary of Royal Dutch Shell ​ 16,168 24 % 20,512 29 % 32,156 24 % 41,236 30 % Galp Sinopec Brasil Services B.V. ​ 8,881 13 % 8,881 13 % 17,665 13 % 17,763 13 %

Operating Leases (Tables)

Operating Leases (Tables)	6 Months Ended
	Jun. 30, 2021
Operating Leases
Schedule of Partnership's revenues by time charter and bareboat charters and other revenues	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (U.S. Dollars in thousands) 2021 2020 2021 2020 Time charter revenues (service element included) ​ $ 55,264 ​ $ 59,001 ​ $ 109,733 ​ $ 114,978 Bareboat revenues ​ ​ 11,249 ​ ​ 11,249 ​ ​ 22,378 ​ ​ 22,498 Other revenues (loss of hire insurance recoveries and other income) ​ 4,424 ​ 9 ​ 10,307 ​ 607 Total revenues ​ $ 70,937 ​ $ 70,259 ​ $ 142,418 ​ $ 138,083
Schedule of minimum contractual future revenues	​ ​ ​ ​ ​ (U.S. Dollars in thousands) ​ ​ 2021 (excluding the six months ended June 30, 2021) ​ $ 131,436 2022 ​ ​ 184,259 2023 ​ ​ 99,805 2024 ​ ​ 102,560 2025 ​ ​ 76,916 2026 and thereafter ​ ​ 46,775 Total $ 641,751
Schedule of maturity analysis of partnership's lease liabilities	A maturity analysis of the Partnership’s lease liabilities from leased-in equipment as of June 30, 2021 is as follows: ​ ​ ​ ​ ​ (U.S. Dollars in thousands) ​ 2021 (excluding the six months ended June 30, 2021) ​ $ 352 2022 ​ 703 2023 ​ 703 2024 ​ 703 2025 ​ ​ 703 2026 and thereafter ​ ​ 59 Total ​ $ 3,223 Less imputed interest ​ 163 Carrying value of operating lease liabilities ​ $ 3,060

Other Finance Expenses (Tables)

Other Finance Expenses (Tables)	6 Months Ended
	Jun. 30, 2021
Other Finance Expenses
Schedule of components of interest cost	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, (U.S. Dollars in thousands) 2021 2020 2021 2020 Interest expense ​ $ 6,148 ​ $ 7,886 ​ $ 12,418 ​ $ 17,712 Amortization of debt issuance cost and fair value of debt assumed ​ 656 ​ 626 ​ 1,758 ​ 1,262 Total interest cost ​ $ 6,804 ​ $ 8,512 ​ $ 14,176 ​ $ 18,974
Schedule of components of other finance expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, (U.S. Dollars in thousands) 2021 2020 2021 2020 Bank fees, charges ​ $ 132 ​ $ 137 ​ $ 215 ​ $ 184 Commitment fees ​ 118 62 ​ 194 ​ 123 Total other finance expense ​ $ 250 $ 199 ​ $ 409 ​ $ 307

Derivative Instruments (Tables)

Derivative Instruments (Tables)	6 Months Ended
	Jun. 30, 2021
Derivative Instruments
Schedule of realized and unrealized gains and losses recognized in earnings	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, (U.S. Dollars in thousands) 2021 2020 2021 2020 Realized gain (loss): ​ ​ ​ ​ ​ Interest rate swap contracts ​ $ (2,087) ​ $ (191) ​ $ (5,996) ​ $ 12 Foreign exchange forward contracts ​ — ​ (109) ​ — ​ (109) Total realized gain (loss): ​ (2,087) ​ (300) ​ (5,996) ​ (97) Unrealized gain (loss): ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ (178) ​ (3,457) ​ 11,742 ​ (26,438) Foreign exchange forward contracts ​ — ​ 665 ​ — ​ (247) Total unrealized gain (loss): ​ (178) ​ (2,792) ​ 11,742 ​ (26,685) Total realized and unrealized gain (loss) on derivative instruments: ​ $ (2,265) ​ $ (3,092) ​ $ 5,746 ​ $ (26,782)

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Measurements
Carrying amounts and estimated fair values of financial instruments	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ December 31, 2020 ​ Carrying Fair Carrying Fair (U.S. Dollars in thousands) Amount Value Amount Value Recurring: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Financial assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 51,589 ​ $ 51,589 ​ $ 52,583 ​ $ 52,583 Non-current derivative assets: ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 168 ​ 168 ​ — ​ — Financial liabilities: ​ ​ ​ ​ ​ ​ ​ ​ Current derivative liabilities: ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 9,984 ​ 9,984 ​ 10,695 ​ 10,695 Non-current derivative liabilities: ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 8,495 ​ 8,495 ​ 19,358 ​ 19,358 Long-term debt, current and non-current ​ 1,003,211 ​ 1,003,211 ​ 1,036,118 ​ 1,036,118 Non-Recurring: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Non-current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vessel ​ ​ 48,156 ​ ​ 48,156 ​ ​ — ​ ​ —
Schedule of assets and liabilities measured at fair value on recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements ​ ​ ​ ​ at Reporting Date Using ​ ​ ​ ​ ​ Quoted Price ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ in Active ​ Significant ​ ​ ​ ​ ​ Carrying ​ Markets for ​ Other ​ Significant ​ ​ Value ​ Identical ​ Observable ​ Unobservable ​ ​ June 30, ​ Assets ​ Inputs ​ Inputs (U.S. Dollars in thousands) 2021 (Level 1) (Level 2) (Level 3) Recurring: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Financial assets: ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 51,589 ​ $ 51,589 ​ $ — ​ $ — Current derivative assets: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 168 ​ — ​ 168 ​ — Financial liabilities: ​ ​ ​ ​ ​ ​ ​ Non-current derivative liabilities: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 9,984 ​ — ​ 9,984 ​ — Non-current derivative liabilities: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 8,495 ​ — ​ 8,495 ​ — Long-term debt, current and non-current ​ 1,003,211 ​ — ​ 1,003,211 ​ — Non-Recurring: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Non-current assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vessel ​ ​ 48,156 ​ ​ — ​ ​ — ​ ​ 48,156 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements ​ ​ ​ ​ at Reporting Date Using ​ ​ ​ ​ ​ Quoted Price ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ in Active ​ Significant ​ ​ ​ ​ ​ Carrying ​ Markets for ​ Other ​ Significant ​ ​ Value ​ Identical ​ Observable ​ Unobservable ​ ​ December 31, ​ Assets ​ Inputs ​ Inputs (U.S. Dollars in thousands) 2020 (Level 1) (Level 2) (Level 3) Financial assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 52,583 ​ $ 52,583 ​ $ — ​ $ — Current derivative assets: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ — ​ — ​ — ​ — Foreign exchange forward contracts ​ — ​ — ​ — ​ — Non-current derivative assets: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ — ​ — ​ — ​ — Financial liabilities: ​ ​ ​ ​ ​ ​ ​ Current derivative liabilities: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 10,695 ​ — ​ 10,695 ​ — Non-current derivative liabilities: ​ ​ ​ ​ ​ ​ ​ Interest rate swap contracts ​ 19,358 ​ — ​ 19,358 ​ — Long-term debt, current and non-current ​ 1,036,118 ​ — ​ 1,036,118 ​ — ​
Schedule of valuation techniques and significant unobservable inputs used in the valuation of Level 3 assets measured at fair value on a non-recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Significant ​ ​ ​ Fair ​ ​ ​ unobservable ​ ​ (U.S. Dollars in thousands) ​ Value ​ Valuation technique ​ inputs: ​ WACC (1) Non-Recurring: ​ ​ Non-current assets: ​ ​ Windsor Knutsen ​ $ 48,156 Discounted cash flow Discount rate 6.38 %

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2021
Income Taxes
Significant Components of Current and Deferred Income Tax Expense Attributable to Income from Continuing Operations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ (U.S. Dollars in thousands) 2021 2020 2021 2020 Income before income taxes ​ $ (10,664) ​ $ 21,686 ​ $ 17,480 ​ $ 15,550 ​ Income tax (expense) ​ ​ (261) ​ ​ (3) ​ ​ (264) ​ ​ (6) ​ Effective tax rate ​ $ 2 % $ 0 % $ (2) % $ 0 %
Summary of Taxation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ (U.S. Dollars in thousands) ​ 2021 ​ 2020 ​ 2021 ​ 2020 ​ Income tax benefit (expense) - Norwegian tonnage tax $ (258) $ — $ (258) $ — ​ Income tax benefit (expense) - UK ​ ​ (3) ​ ​ (3) ​ ​ (6) ​ ​ (6) ​ Income tax benefit (expense) $ (261) $ (3) $ (264) $ (6) ​ Effective tax rate ​ ​ 2 % ​ 0 % ​ (2) % ​ 0 %

Vessels and Equipment (Tables)

Vessels and Equipment (Tables)	6 Months Ended
	Jun. 30, 2021
Vessels and Equipment
Schedule of vessels and equipment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vessels & ​ Accumulated ​ ​ Accumulated write ​ ​ ​ (U.S. Dollars in thousands) equipment ​ depreciation ​ down ​ Net Vessels Vessels, December 31, 2019 ​ $ 2,129,012 $ (451,524) $ — $ 1,677,488 Additions ​ 115,277 ​ — ​ ​ — ​ 115,277 Drydock costs ​ 5,764 ​ — ​ ​ — ​ 5,764 Disposals ​ — ​ — ​ ​ — ​ — Depreciation for the year ​ — ​ (89,743) ​ ​ — ​ (89,743) Vessels, December 31, 2020 ​ $ 2,250,053 ​ $ (541,267) ​ $ — ​ $ 1,708,786 Additions (1) ​ 6,748 ​ — ​ ​ — ​ 6,748 Drydock costs ​ 3,428 ​ — ​ ​ — ​ 3,428 Disposals ​ (2,641) ​ 2,641 ​ ​ — ​ — Depreciation and write down for the period (2) ​ — ​ (47,515) ​ ​ (29,421) ​ (76,936) Vessels, June 30, 2021 ​ $ 2,257,588 ​ $ (586,141) ​ $ (29,421) ​ $ 1,642,026
Schedule of drydocking activity	​ ​ ​ ​ ​ ​ ​ ​ (U.S. Dollars in thousands) At June 30, 2021 At December 31, 2020 Balance at the beginning of the year ​ $ 17,106 ​ $ 18,523 Costs incurred for dry docking ​ 3,428 ​ 2,724 Costs allocated to drydocking as part of acquisition of asset ​ — ​ 3,040 Drydock amortization ​ (3,948) ​ (7,181) Balance at the end of the year ​ $ 16,586 ​ $ 17,106

Intangible Assets (Tables)

Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2021
Intangible Assets
Schedule of intangible assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Above market ​ Above market ​ ​ ​ ​ time charter time charter Total (U.S. Dollars in thousands) ​ Tordis Knutsen ​ Vigdis Knutsen ​ intangibles Intangibles, December 31, 2019 ​ $ 608 ​ $ 678 ​ $ 1,286 Amortization for the year ​ (303) ​ (302) ​ (605) Intangibles, December 31, 2020 ​ $ 305 ​ $ 376 ​ $ 681 Amortization for the period ​ (152) ​ (151) ​ (303) Intangibles, June 30, 2021 ​ $ 153 ​ $ 225 ​ $ 378
Summary of estimated future amortization of intangible assets	​ ​ ​ ​ ​ (U.S. Dollars in thousands) ​ Remainder of 2021 ​ 303 2022 ​ 75 Total ​ $ 378
Schedule of contract liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortization for ​ Amortization for ​ ​ ​ Balance of ​ the year ended ​ Balance of ​ the six Months ​ Balance of ​ ​ December 31, ​ December 31, ​ December 31, ​ ended June 30, ​ June 30, (U.S. Dollars in thousands) ​ 2019 ​ 2020 ​ 2020 ​ 2021 ​ 2021 Contract liabilities: ​ ​ ​ ​ ​ Unfavourable contract rights ​ $ (5,203) ​ $ 1,517 ​ $ (3,686) ​ $ 758 ​ $ (2,928) Total amortization income ​ ​ $ 1,517 ​ ​ $ 758 ​
Schedule of expected amortization of contract liabilities	​ ​ ​ ​ ​ (U.S. Dollars in thousands) ​ Remainder of 2021 ​ 759 2022 ​ 1,518 2023 ​ 651 2024 ​ — 2025 ​ — 2026 ​ — Total ​ $ 2,928

Long-Term Debt (Tables)

Long-Term Debt (Tables)	6 Months Ended
	Jun. 30, 2021
Long-Term Debt
Schedule of long-term debt	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, (U.S. Dollars in thousands) Vessel 2021 2020 $320 million loan facility ​ Windsor Knutsen, Bodil Knutsen, Carmen Knutsen, Fortaleza Knutsen, Recife Knutsen, Ingrid Knutsen ​ $ 237,190 ​ $ 252,245 $55 million revolving credit facility ​ ​ ​ 5,000 ​ 34,279 Hilda loan facility Hilda Knutsen ​ 75,385 ​ 78,462 Torill loan facility Torill Knutsen ​ 78,333 ​ 81,667 $172.5 million loan facility Dan Cisne, Dan Sabia ​ 52,140 ​ 58,340 Raquel loan facility Raquel Knutsen ​ — ​ 52,725 Tordis loan facility Tordis Knutsen ​ 73,341 ​ 75,871 Vigdis loan facility Vigdis Knutsen ​ 74,606 ​ 77,136 Lena loan facility Lena Knutsen ​ 73,500 ​ 75,950 Brasil loan facility Brasil Knutsen ​ 47,855 ​ 50,997 Anna loan facility Anna Knutsen ​ 60,157 ​ 62,196 Tove loan facility ​ Tove Knutsen ​ ​ 84,066 ​ ​ 86,250 $25 million revolving credit facility with NTT ​ 25,000 ​ 25,000 $25 million revolving credit facility with Shinsei ​ ​ ​ ​ 25,000 ​ ​ 25,000 Raquel Sale & Leaseback ​ Raquel Knutsen ​ ​ 91,638 ​ ​ — Total long-term debt ​ $ 1,003,211 ​ $ 1,036,118 Less: current installments ​ 353,643 ​ 186,723 Less: unamortized deferred loan issuance costs ​ 2,273 ​ 2,535 Current portion of long-term debt ​ 351,370 ​ 184,188 Amounts due after one year ​ 649,568 ​ 849,395 Less: unamortized deferred loan issuance costs ​ 3,220 ​ 3,238 Long-term debt, less current installments, and unamortized deferred loan issuance costs ​ $ 646,348 ​ $ 846,157
Schedule of partnership's outstanding debt repayable	The Partnership’s outstanding debt of $1,003.2 million as of June 30, 2021 is repayable as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (U.S. Dollars in thousands) ​ Sale & Leaseback Period repayment Balloon repayment Total Remainder of 2021 $ 2,433 ​ $ 43,142 $ 70,811 ​ $ 116,386 2022 ​ 4,960 ​ ​ 70,348 ​ 236,509 ​ ​ 311,817 2023 ​ 5,177 ​ ​ 54,672 ​ 230,906 ​ ​ 290,755 2024 ​ 5,418 ​ ​ 13,011 ​ 123,393 ​ ​ 141,822 2025 ​ 5,640 ​ ​ 3,276 ​ 65,506 ​ ​ 74,422 2026 and thereafter ​ 68,009 ​ ​ — ​ — ​ ​ 68,009 Total ​ $ 91,637 ​ $ 184,449 ​ $ 727,125 ​ $ 1,003,211

Related Party Transactions (Tab

Related Party Transactions (Tables)	6 Months Ended
	Jun. 30, 2021
Related Party Transactions
Schedule of Related Party Costs and Expenses	Net income (expense) from related parties included in the unaudited condensed consolidated statements of operations for the three and six months ended June 30, 2021 and 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, (U.S. Dollars in thousands) 2021 2020 2021 ​ 2020 Statements of operations: ​ ​ ​ ​ ​ ​ ​ ​ Time charter and bareboat revenues: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Time charter income from KNOT (1) ​ $ 1,866 ​ $ 105 ​ $ 1,866 ​ $ 4,883 Operating expenses: ​ ​ ​ ​ ​ ​ ​ ​ Vessel operating expenses (2) ​ ​ 5,000 ​ ​ 4,392 ​ ​ 7,752 ​ ​ 6,856 Technical and operational management fee from KNOT to Vessels (3) ​ 2,106 ​ 1,703 ​ 4,214 ​ 3,406 Operating expenses from other related parties (4) ​ ​ 172 ​ ​ 66 ​ ​ 299 ​ ​ 229 General and administrative expenses: ​ ​ ​ ​ ​ ​ ​ ​ Administration fee from KNOT Management (5) ​ 379 ​ 244 ​ 666 ​ 474 Administration fee from KOAS (5) ​ 201 ​ 165 ​ 395 ​ 323 Administration fee from KOAS UK (5) ​ 19 ​ 31 ​ 37 ​ 61 Administration and management fee from KNOT (6) ​ 20 ​ 40 ​ 29 ​ 85 Total income (expenses) ​ $ (6,031) ​ $ (6,536) ​ $ (11,526) ​ $ (6,551) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ At June 30, ​ At December 31, (U.S. Dollars in thousands) 2021 2020 Balance Sheet: ​ ​ Vessels: ​ ​ Drydocking supervision fee from KNOT (7) ​ $ 134 ​ $ 47 Total ​ $ 134 ​ $ 47 (1) Time charter income from KNOT: On December 17, 2018, the Partnership's subsidiary that owns the Windsor Knutsen and Royal Dutch Shell ("Shell") agreed to suspend the vessel's time charter contract. The suspension period commenced March 4, 2019 and ended April 5, 2020, when the vessel was redelivered to Shell. During the suspension period, the Windsor Knutsen operated under a time charter contract with Knutsen Shuttle Tankers Pool AS on the same terms as the existing time charter contract with Shell. After completing its drydock in the second quarter of 2021, the Bodil Knutsen has operated under a time charter with Knutsen Shuttle Tankers Pool AS for an initial three-month period commencing on May 13, 2021 and then on a rolling one-month basis. (2) Vessel operating expenses: KNOT Management or KNOT Management Denmark provides technical and operational management of the vessels on time charter including crewing and crew training services. (3) Technical and operational management fee, from KNOT Management or KNOT Management Denmark to Vessels : KNOT Management or KNOT Management Denmark provides technical and operational management of the vessels on time charter including crewing, purchasing, maintenance and other operational service. In addition, there is also a charge for 24-hour emergency response services provided by KNOT Management for all vessels managed by KNOT Management. (4) Operating expenses from other related parties : Simsea Real Operations AS, a company jointly owned by the Partnership’s Chairman of the Board, Trygve Seglem, and by other third-party shipping companies in Haugesund, provides simulation, operational training assessment and other certified maritime courses for seafarers. The cost is course fees for seafarers. Knutsen OAS Crewing AS, a subsidiary of TSSI, provides administrative services related to East European crew on vessels operating on time charter contracts. The cost is a fixed fee per month per East European crew onboard the vessel. (5) Administration fee from KNOT Management, Knutsen OAS Shipping AS (“KOAS”) and Knutsen OAS (UK) Ltd. (“KOAS UK”) : Administration costs include compensation and benefits of KNOT Management’s management and administrative staff as well as other general and administration expenses. Some benefits are also provided by KOAS and KOAS UK . Net administration costs are total administration cost plus a 5% margin, reduced for the total fees for services delivered by the administration staffs and the estimated shareholder costs for KNOT that have not been allocated. As such, the level of net administration costs as a basis for the allocation can vary from year to year based on the administration and financing services offered by KNOT to all the vessels in its fleet each year. KNOT Management also charges each subsidiary a fixed annual fee for the preparation of the statutory financial statement. (6) Administration and management fee from KNOT Management and KNOT Management Denmark : For bareboat charters, the shipowner is not responsible for providing crewing or other operational services and the customer is responsible for all vessel operating expenses and voyage expenses. However, each of the vessels under bareboat charters is subject to a management and administration agreement with either KNOT Management or KNOT Management Denmark, pursuant to which these companies provide general monitoring services for the vessels in exchange for an annual fee. (7) Drydocking supervision fee from KNOT and KOAS : KNOT and KOAS provide supervision and hire out service personnel during drydocking of the vessels. The fee is calculated as a daily fixed fee.
Schedule of amounts due from and due to related parties	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ At June 30, ​ At December 31, (U.S. Dollars in thousands) 2021 2020 Balance Sheet: ​ ​ Trading balances due from KOAS ​ $ 55 ​ $ 170 Trading balances due from KNOT and affiliates (1) ​ 1,707 ​ 5,556 Amount due from related parties ​ $ 1,762 ​ $ 5,726 Trading balances due to KOAS ​ $ 2,489 ​ $ 1,596 Trading balances due to KNOT and affiliates ​ 961 ​ 544 Amount due to related parties ​ $ 3,450 ​ $ 2,140 ​ (1) On December 31, 2020, the Partnership's wholly owned subsidiary, KNOT Shuttle Tankers AS, acquired KNOT's 100% interest in KNOT Shuttle Tankers 34 AS ("KNOT 34"), the company that owns and operates the Tove Knutsen Trading balances due from KNOT and affiliates as of December 31, 2020 includes the post-closing settlement amount of $3.6 million related to the acquisition of the Tove Knutsen. ​
Schedule of other current asset balances from related parties	​ ​ ​ ​ ​ ​ ​ ​ ​ At June 30, At December 31, (U.S. Dollars in thousands) ​ 2021 ​ 2020 Balance Sheet: ​ ​ Trading balances due from KNOT and affiliates $ 893 ​ $ 1,697 Trading balances due from KOAS ​ 353 ​ 450 Other current assets from related parties ​ $ 1,246 ​ $ 2,147
Schedule of Trade Accounts Payable to Related Parties	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ At June 30, ​ At December 31, (U.S. Dollars in thousands) 2021 2020 Balance Sheet: ​ ​ ​ ​ Trading balances due to KOAS ​ $ 920 ​ $ 1,304 Trading balances due to KNOT and affiliates ​ 522 ​ 902 Trade accounts payables to related parties ​ $ 1,442 ​ $ 2,206

Earnings per Unit and Cash Di_2

Earnings per Unit and Cash Distributions (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings per Unit and Cash Distributions
Schedule of calculations of basic and diluted earnings per unit	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, (U.S. Dollars in thousands, except per unit data) 2021 2020 2021 2020 Net income (loss) ​ $ (10,925) ​ $ 21,683 ​ $ 17,216 ​ $ 15,544 Less: Series A Preferred unitholders’ interest in net income ​ ​ 1,759 ​ ​ 1,800 ​ ​ 3,559 ​ ​ 3,600 Net income attributable to the unitholders of KNOT Offshore Partners LP ​ ​ (12,684) ​ ​ 19,883 ​ ​ 13,657 ​ ​ 11,944 Less: Distributions (2) ​ ​ 18,150 ​ ​ 18,034 ​ ​ 36,184 ​ ​ 36,068 Under (over) distributed earnings ​ ​ (30,834) ​ ​ 1,849 ​ ​ (22,527) ​ ​ (24,124) Under (over) distributed earnings attributable to: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common unitholders (3) ​ ​ (30,268) ​ ​ 1,815 ​ ​ (22,114) ​ ​ (23,679) General Partner ​ ​ (566) ​ ​ 34 ​ ​ (413) ​ ​ (445) Weighted average units outstanding (basic) (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Common unitholders ​ ​ 32,782 ​ ​ 32,694 ​ ​ 32,738 ​ ​ 32,694 General Partner ​ ​ 615 ​ ​ 615 ​ ​ 615 ​ ​ 615 Weighted average units outstanding (diluted) (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common unitholders (4) ​ ​ 36,619 ​ ​ 36,596 ​ ​ 36,594 ​ ​ 36,648 General Partner ​ ​ 615 ​ ​ 615 ​ ​ 615 ​ ​ 615 Earnings per unit (basic) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common unitholders ​ $ (0.38) ​ $ 0.60 ​ $ 0.41 ​ $ 0.36 General Partner ​ ​ (0.38) ​ ​ 0.60 ​ ​ 0.41 ​ ​ 0.36 Earnings per unit (diluted): ​ ​ ​ ​ ​ ​ ​ ​ ​ Common unitholders (4) ​ $ (0.38) ​ $ 0.58 ​ $ 0.41 ​ $ 0.36 General Partner ​ ​ (0.38) ​ ​ 0.60 ​ ​ 0.41 ​ ​ 0.36 Cash distributions declared and paid in the period per unit (5) ​ ​ 0.52 ​ ​ 0.52 ​ ​ 1.04 ​ ​ 1.04 Subsequent event: Cash distributions declared and paid per unit relating to the period (6) ​ ​ 0.52 ​ ​ 0.52 ​ ​ 1.04 ​ ​ 1.04 (1) Earnings per unit have been calculated in accordance with the cash distribution provisions set forth in the Partnership Agreement. (2) This refers to distributions made or to be made in relation to the period irrespective of the declaration and payment dates and based on the number of units outstanding at the record date. This includes cash distributions to the IDR holder (KNOT) for the three months ended June 30, 2021 and 2020 of $0.7 million and for the six months ended June 30, 2021 and 2020 of $1.4 million. (3) This includes the net income attributable to the IDR holder. The net income attributable to IDRs for the three months ended June 30, 2021 and 2020 was $0.7 million and for the six months ended June 30, 2021 and 2020 was $1.4 . (4) Diluted weighted average units outstanding and earnings per unit diluted for the three and six months ended June 30, 2021 and 2020 does not reflect any potential common shares relating to the convertible preferred units since the assumed issuance of any additional shares would be anti-dilutive. (5) Refers to cash distributions declared and paid during the period. (6) Refers to cash distributions declared and paid subsequent to the period end. On May 27, 2021, Tortoise Direct Opportunities Fund LP, the holder of 416,677 of the Partnership’s Series A Convertible Preferred Units, sold 208,333 of its Series A Preferred Units to KNOT and converted 208,334 Series A Preferred Units to 215,292 common units based on a conversion rate of 1.0334.

Acquisitions (Tables)

Acquisitions (Tables)	6 Months Ended
	Jun. 30, 2021
Acquisitions
Schedule of purchase price for the transaction	​ ​ ​ ​ ​ ​ Final ​ ​ Tove Knutsen ​ ​ December 31, (U.S. Dollars in thousands) ​ 2020 Purchase consideration (1) ​ $ 21,898 Less: Fair value of net assets acquired: ​ Vessels and equipment (2) ​ 117,978 Intangibles: Above market time charter ​ — Cash ​ 804 Inventories ​ 136 Derivatives assets (liabilities) ​ (3,537) Others current assets ​ 270 Amounts due from related parties ​ — Long-term debt ​ (93,139) Long-term debt from related parties ​ — Deferred debt issuane ​ 769 Trade accounts payable ​ (430) Accrued expenses ​ (622) Amounts due to related parties ​ ​ (331) Subtotal ​ ​ 21,898 Difference between the purchase price and fair value of net assets acquired ​ $ — (1) The purchase consideration comprises the following: ​ ​ ​ ​ ​ ​ Final ​ ​ ToveKnutsen ​ ​ December 31, (U.S. Dollars in thousands) ​ 2020 Cash consideration paid to KNOT (from KNOP) ​ $ 25,430 Purchase price adjustments ​ (3,596) Acquisition-related costs ​ 64 Purchase price ​ $ 21,898 (2) Vessel and Equipment includes allocations to dry docking (in thousands) of $3,040 .

Unit activity (Tables)

Unit activity (Tables)	6 Months Ended
	Jun. 30, 2021
Unit Activity
Schedule of movement in number of common units, general partner units and Series A Preferred Units	The following table shows the movement in number of common units, general partner units and Series A Preferred Units from December 31, 2020 until June 30, 2021. ​ ​ ​ ​ ​ ​ ​ (in units) Common Units General Partner Units Convertible Preferred Units December 31, 2020 32,694,094 615,117 3,750,000 May 27, 2021: Conversion of Series A Preferred Units 215,292 — (208,334) June 30, 2021 32,909,386 615,117 3,541,666 ​

Trade Accounts Receivable and_2

Trade Accounts Receivable and Other Current Assets (Tables)	6 Months Ended
	Jun. 30, 2021
Trade Accounts Receivable and Other Current Assets
Schedule of Other Current Assets	​ ​ ​ ​ ​ ​ ​ ​ (U.S. Dollars in thousands) At June 30, 2021 At December 31, 2020 Insurance claims for recoveries ​ 7,477 ​ — Refund of value added tax ​ 1,762 ​ 1,429 Prepaid expenses ​ 1,392 ​ 1,050 Other receivables ​ 3,750 ​ 3,032 Total other current assets ​ $ 14,381 ​ $ 5,511

Description of Business (Detail

Description of Business (Details) $ in Millions	1 Months Ended
	Apr. 30, 2013item	Aug. 26, 2021USD ($)	Jun. 30, 2021item	Dec. 31, 2020item
Description of Business
Ownership interest in shuttle tankers acquired at formation (as a percent)	100.00%
Number of shuttle tankers acquired at formation	4
Number of operating vessels			17	16
Undrawn portion of revolving credit facilities | $		$ 50

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details)	6 Months Ended
	Jun. 30, 2021
Vessels and Equipment
Asset's estimated useful life	25 years
Change in Accounting Method Accounted for as Change in Estimate [Member]
Vessels and Equipment
Asset's estimated useful life	23 years

Segment Information (Details)

Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021USD ($)item	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)segmentitem	Jun. 30, 2020USD ($)	Dec. 31, 2020item
Segment Information
Revenues	$ 70,937	$ 70,259	$ 142,418	$ 138,083
Number Of Vessels | item	17		17		16
Number of reportable segments | segment			1
Eni Trading and Shipping S.p.A.
Segment Information
Revenues	$ 10,915	10,953	$ 21,748	22,088
Fronape International Company, a subsidiary of Petrobras Transporte S.A.
Segment Information
Revenues	11,249	11,249	22,378	22,498
Repsol Sinopec Brasil, S.A., a subsidiary of Repsol Sinopec Brasil, B.V.
Segment Information
Revenues	9,282	9,285	18,075	15,178
Brazil Shipping I Limited, a subsidiary of Royal Dutch Shell
Segment Information
Revenues	16,168	20,512	32,156	41,236
Galp Sinopec Brasil Services B.V.
Segment Information
Revenues	$ 8,881	$ 8,881	$ 17,665	$ 17,763
Revenues [Member] | Eni Trading and Shipping S.p.A. | Customer Concentration Risk [Member]
Segment Information
Benchmark percentage of revenues and combined revenues concentration	16.00%	16.00%	16.00%	16.00%
Revenues [Member] | Fronape International Company, a subsidiary of Petrobras Transporte S.A. | Customer Concentration Risk [Member]
Segment Information
Benchmark percentage of revenues and combined revenues concentration	17.00%	16.00%	17.00%	16.00%
Revenues [Member] | Repsol Sinopec Brasil, S.A., a subsidiary of Repsol Sinopec Brasil, B.V. | Customer Concentration Risk [Member]
Segment Information
Benchmark percentage of revenues and combined revenues concentration	14.00%	13.00%	14.00%	11.00%
Revenues [Member] | Brazil Shipping I Limited, a subsidiary of Royal Dutch Shell | Customer Concentration Risk [Member]
Segment Information
Benchmark percentage of revenues and combined revenues concentration	24.00%	29.00%	24.00%	30.00%
Revenues [Member] | Galp Sinopec Brasil Services B.V. | Customer Concentration Risk [Member]
Segment Information
Benchmark percentage of revenues and combined revenues concentration	13.00%	13.00%	13.00%	13.00%
Minimum [Member] | Revenues [Member] | Customer Concentration Risk [Member]
Segment Information
Benchmark percentage of revenues and combined revenues concentration	10.00%	10.00%	10.00%	10.00%

Operating Leases (Details)

Operating Leases (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating Leases
Revenue from contract with customers	$ 66,513	$ 70,250	$ 132,111	$ 137,476
Other revenues (loss of hire insurance recoveries and other income)	4,424	9	10,307	607
Total revenues	70,937	70,259	142,418	138,083
Time charter revenues (service element included)
Operating Leases
Revenue from contract with customers	55,264	59,001	109,733	114,978
Bareboat revenues
Operating Leases
Revenue from contract with customers	$ 11,249	$ 11,249	$ 22,378	$ 22,498

Operating Leases - Minimum Cont

Operating Leases - Minimum Contractual Future Revenues (Details) $ in Thousands	Jun. 30, 2021USD ($)
Minimum contractual future revenues
2021 (excluding the six months ended June 30, 2021)	$ 131,436
2022	184,259
2023	99,805
2024	102,560
2025	76,916
2026 and thereafter	46,775
Total	$ 641,751

Operating Leases - Additional I

Operating Leases - Additional Information (Details)	6 Months Ended
	Jun. 30, 2021
Fortaleza Knutsen
Operating Leases
Current bareboat charter expiration year	2023
Recife Knutsen
Operating Leases
Current bareboat charter expiration year	2023
Bodil Knutsen
Operating Leases
Time charter expiration year under options to extend	2024
Carmen Knutsen
Operating Leases
Current time charter expiration year	2023
Time charter expiration year under options to extend	2026
Hilda Knutsen
Operating Leases
Current time charter expiration year	2022
Time charter expiration year under options to extend	2025
Torill Knutsen [Member]
Operating Leases
Current time charter expiration year	2022
Time charter expiration year under options to extend	2024
Dan Cisne [Member]
Operating Leases
Current bareboat charter expiration year	2023
Dan Sabia [Member]
Operating Leases
Current bareboat charter expiration year	2024
Ingrid Knutsen [Member]
Operating Leases
Current time charter expiration year	2024
Time charter expiration year under options to extend	2029
Raquel Knutsen
Operating Leases
Current time charter expiration year	2025
Time charter expiration year under options to extend	2030
Tordis Knutsen [Member]
Operating Leases
Fixed term of contract	3 years
Current time charter expiration year	2022
Time charter expiration year under options to extend	2023
Vigdis Knutsen [Member]
Operating Leases
Fixed term of contract	3 years
Current time charter expiration year	2022
Time charter expiration year under options to extend	2023
Lena Knutsen [Member]
Operating Leases
Fixed term of contract	3 years
Current time charter expiration year	2022
Time charter expiration year under options to extend	2023
Brasil Knutsen [Member]
Operating Leases
Current time charter expiration year	2022
Time charter expiration year under options to extend	2028
Anna Knutsen [Member]
Operating Leases
Current time charter expiration year	2022
Time charter expiration year under options to extend	2028
Tove Knutsens [Member]
Operating Leases
Current time charter expiration year	2027
Time charter expiration year under options to extend	2040

Operating Leases - Lease obliga

Operating Leases - Lease obligations (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Operating Leases
Right-of-use asset	$ 3,061	$ 3,061	$ 1,490
Lease liability	$ 3,060	$ 3,060
Weighted average discount rate (as a percent)	2.30%	2.30%
Weighted average remaining lease term	4 years 7 months 6 days	4 years 7 months 6 days
Operating lease payments	$ 200	$ 300
Partnership's lease liabilities from leased-in equipment
2021 (excluding the six months ended June 30, 2021)	352	352
2022	703	703
2023	703	703
2024	703	703
2025	703	703
2026 and thereafter	59	59
Total	3,223	3,223
Less imputed interest	163	163
Carrying value of operating lease liabilities	$ 3,060	$ 3,060

Insurance Proceeds (Details)

Insurance Proceeds (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Dec. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Insurance Proceeds
Deductible period under business interruption insurance				14 days
Loss of hire insurance payments recorded as a component of total revenues		$ 4,397		$ 10,279
Net vessel operating expense		17,394	$ 13,112	35,954	$ 28,746
Windsor Knutsen
Insurance Proceeds
Deductible period under business interruption insurance	14 days
Loss of hire insurance payments recorded as a component of total revenues		3,700		8,700
Recoveries for repairs		2,500		4,100
Claimed insurance recoveries including vessel operating expense		4,000		4,000
Net vessel operating expense				100
Windsor Knutsen | Maximum [Member]
Insurance Proceeds
Deductible period under business interruption insurance	180 days
Tove Knutsen
Insurance Proceeds
Loss of hire insurance payments recorded as a component of total revenues		700		1,500
Recoveries for repairs		300		500
Claimed insurance recoveries including vessel operating expense		400		400
Net vessel operating expense				100
Bodil Knutsen
Insurance Proceeds
Recoveries for repairs		$ 500		500
Claimed insurance recoveries including vessel operating expense				300
Net vessel operating expense				$ 200

Other Finance Expenses - Compon

Other Finance Expenses - Components Interest Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Other Finance Expenses
Interest expense	$ 6,148	$ 7,886	$ 12,418	$ 17,712
Amortization of debt issuance cost and fair value of debt assumed	656	626	1,758	1,262
Total interest cost	$ 6,804	$ 8,512	$ 14,176	$ 18,974

Other Finance Expenses - Comp_2

Other Finance Expenses - Components of other finance expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Other Finance Expenses
Bank fees, charges	$ 132	$ 137	$ 215	$ 184
Commitment fees	118	62	194	123
Total other finance expense	$ 250	$ 199	$ 409	$ 307

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Details) - Interest rate swap contracts [Member] - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Derivative Instruments
Carrying amount of derivative liabilities	$ 18.3	$ 30.1
Notional amount	$ 472.6	$ 516.2

Derivative Instruments - Realiz

Derivative Instruments - Realized and Unrealized Gains and Losses Recognized in Earnings (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net gain (loss) on derivative instruments
Realized gain (loss)	$ (2,087)	$ (300)	$ (5,996)	$ (97)
Unrealized gain (loss)	(178)	(2,792)	11,742	(26,685)
Total realized and unrealized gain (loss) on derivative instruments	(2,265)	(3,092)	5,746	(26,782)
Interest rate swap contracts [Member]
Net gain (loss) on derivative instruments
Realized gain (loss)	(2,087)	(191)	(5,996)	12
Unrealized gain (loss)	$ (178)	(3,457)	$ 11,742	(26,438)
Foreign exchange forward contracts [Member]
Net gain (loss) on derivative instruments
Realized gain (loss)		(109)		(109)
Unrealized gain (loss)		$ 665		$ (247)

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Partnership 's Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Financial assets:
Non-current derivative assets	$ 168
Financial liabilities:
Current derivative liabilities	9,984	$ 10,695
Non-current derivative liabilities	8,495	19,358
Vessel	1,642,026	1,708,786	$ 1,677,488
Carrying Amount [Member]
Financial assets:
Cash and cash equivalents	51,589	52,583
Financial liabilities:
Long-term debt, current and non-current	1,003,211	1,036,118
Carrying Amount [Member] | Non-Recurring
Financial liabilities:
Vessel	48,156
Carrying Amount [Member] | Interest rate swap contracts [Member]
Financial assets:
Non-current derivative assets	168
Financial liabilities:
Current derivative liabilities	9,984	10,695
Non-current derivative liabilities	8,495	19,358
Fair Value [Member]
Financial assets:
Cash and cash equivalents	51,589	52,583
Financial liabilities:
Long-term debt, current and non-current	1,003,211	1,036,118
Fair Value [Member] | Non-Recurring
Financial liabilities:
Vessel	48,156
Fair Value [Member] | Interest rate swap contracts [Member]
Financial assets:
Non-current derivative assets	168
Financial liabilities:
Current derivative liabilities	9,984	10,695
Non-current derivative liabilities	$ 8,495	$ 19,358

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Fair Value, assets and liabilities measured on recurring and nonrecurring basis
Deferred debt issuance cost	$ 5,500,000	$ 5,800,000
Restricted cash		$ 0	$ 0
Non-Recurring | Level 3 | Weighted Average [Member]
Fair Value, assets and liabilities measured on recurring and nonrecurring basis
Vessel, Measurement input	6.38
Interest rate swap contracts [Member]
Fair Value, assets and liabilities measured on recurring and nonrecurring basis
Weighted average remaining terms	3 years 9 months 18 days	4 years 3 months 18 days
Interest rate swap contracts [Member] | Minimum [Member]
Fair Value, assets and liabilities measured on recurring and nonrecurring basis
Notional amount per contract	$ 6,200,000	$ 7,000,000
Fixed interest rate	0.71%	0.71%
Interest rate swap contracts [Member] | Maximum [Member]
Fair Value, assets and liabilities measured on recurring and nonrecurring basis
Notional amount per contract	$ 38,800,000	$ 40,100,000
Fixed interest rate	2.90%	2.90%

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Financial assets:
Non-current derivative assets	$ 168
Financial liabilities:
Current derivative liabilities	9,984	$ 10,695
Non-current derivative liabilities	8,495	19,358
Vessel	1,642,026	1,708,786	$ 1,677,488
Carrying Amount [Member]
Financial assets:
Cash and cash equivalents	51,589	52,583
Financial liabilities:
Long-term debt, current and non-current	1,003,211	1,036,118
Fair Value [Member]
Financial assets:
Cash and cash equivalents	51,589	52,583
Financial liabilities:
Long-term debt, current and non-current	1,003,211	1,036,118
Interest rate swap contracts [Member] | Carrying Amount [Member]
Financial assets:
Current derivative assets	168
Non-current derivative assets	168
Financial liabilities:
Current derivative liabilities	9,984	10,695
Non-current derivative liabilities	8,495	19,358
Interest rate swap contracts [Member] | Fair Value [Member]
Financial assets:
Non-current derivative assets	168
Financial liabilities:
Current derivative liabilities	9,984	10,695
Non-current derivative liabilities	8,495	19,358
Non-Recurring | Carrying Amount [Member]
Financial liabilities:
Vessel	48,156
Non-Recurring | Fair Value [Member]
Financial liabilities:
Vessel	48,156
Quoted Price in Active Markets for Identical Assets (Level 1) [Member] | Fair Value [Member]
Financial assets:
Cash and cash equivalents	51,589	52,583
Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member]
Financial liabilities:
Long-term debt, current and non-current	1,003,211	1,036,118
Significant Other Observable Inputs (Level 2) [Member] | Interest rate swap contracts [Member] | Fair Value [Member]
Financial assets:
Current derivative assets	168
Financial liabilities:
Current derivative liabilities	9,984	10,695
Non-current derivative liabilities	8,495	$ 19,358
Level 3 | Non-Recurring | Fair Value [Member]
Financial liabilities:
Vessel	$ 48,156

Fair Value Measurements - Fai_2

Fair Value Measurements - Fair Value transfers into or out of Level 1, Level 2 or Level 3 (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Fair Value Measurements
Transfers amount Fair value assets level 1 to level 2	$ 0	$ 0
Transfers amount Fair value assets level 2 to level 1	0	0
Transfers amount Fair value liabilities level 1 to level 2	0	0
Transfers amount Fair value liabilities level 2 to level 1	0	0
Transfers amount Fair value assets level 3 to level 1	0	0
Transfers amount Fair value liabilities level 3 to level 1	0	0
Transfers amount Fair value liabilities level 3 to level 2	$ 0	$ 0

Fair Value Measurements - Valua

Fair Value Measurements - Valuation of Level 3 assets measured at fair value on a non-recurring basis (Details) - Non-Recurring - Level 3	Jun. 30, 2021USD ($)
Weighted Average [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Vessel, Measurement input	6.38
Windsor Knutsen
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	$ 48,156
Windsor Knutsen | Weighted Average [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Vessel, Measurement input	6.38

Income Taxes - Significant Comp

Income Taxes - Significant Components of Current and Deferred Income Tax Expense Attributable to Income from Continuing Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Taxes
Income before income taxes	$ (10,664)	$ 21,686	$ 17,480	$ 15,550
Income tax benefit (expense)	$ 261	$ 3	$ 264	$ 6
Effective tax rate	2.00%	0.00%	(2.00%)	0.00%

Income Taxes - Additional infor

Income Taxes - Additional information (Details) - USD ($) $ in Thousands	Jan. 01, 2020	Mar. 31, 2021	Mar. 31, 2020	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2017	Mar. 31, 2013
Income Taxes
Entrance tax								$ 3,000
Entrance tax, annual decline in gain				20.00%
Ordinary income tax rate					22.00%	22.00%
Income tax rate, deferred tax liabilities	22.00%				22.00%
Entrance tax payable, current		$ 100	$ 100
Entrance tax payable, non current				$ 300		$ 300
Entrance tax payable related to acquisition							$ 100
Deferred tax assets recognized				$ 0		$ 0

Income Taxes - Summary of Taxat

Income Taxes - Summary of Taxation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Tax Rate Reconciliation
Income tax benefit (expense)	$ (261)	$ (3)	$ (264)	$ (6)
Effective tax rate	2.00%	0.00%	(2.00%)	0.00%
Norwegian Tonnage Tax Regime [Member]
Income Tax Rate Reconciliation
Income tax benefit (expense)	$ (258)		$ (258)
UK tax
Income Tax Rate Reconciliation
Income tax benefit (expense)	$ (3)	$ (3)	$ (6)	$ (6)

Vessels and Equipment - Pledged

Vessels and Equipment - Pledged Assets (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Vessels and Equipment
Book value of assets pledged as security for long-term debt	$ 1,642	$ 1,709

Vessels and Equipment - Long-Te

Vessels and Equipment - Long-Term Debt (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Vessels & equipment - Activity
Vessels and equipment, beginning balance			$ 2,250,053	$ 2,129,012	$ 2,129,012
Additions			6,748		115,277
Drydock costs			3,428		5,764
Disposals			(2,641)
Vessels and equipment, ending balance	$ 2,257,588		2,257,588		2,250,053
Accumulated depreciation - Activity
Accumulated depreciation, beginning balance			(541,267)	(451,524)	(451,524)
Accumulated depreciation, disposals			2,641
Depreciation for the period	(23,831)	$ (22,451)	(47,515)	(44,824)	(89,743)
Accumulated depreciation, ending balance	(586,141)		(586,141)		(541,267)
Accumulated write down - Activity
Depreciation and write down for the period	(29,421)		(29,421)
Accumulated write down, ending balance	(29,421)		(29,421)
Net Vessels - Activity
Net vessel, beginning balance			1,708,786	$ 1,677,488	1,677,488
Additions			6,748		115,277
Drydock costs			3,428		5,764
Depreciation and write down for the period			(76,936)		(89,743)
Net vessel, ending balance	$ 1,642,026		$ 1,642,026		$ 1,708,786

Vessels and Equipment - Drydock

Vessels and Equipment - Drydocking Activity (Details) - Vessels & Equipment - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Movement in Capitalized Drydocking Costs [Roll Forward]
Balance at the beginning of the year	$ 17,106	$ 18,523
Costs incurred for drydocking	3,428	2,724
Costs allocated to drydocking as part of acquisition of asset		3,040
Drydock amortization	(3,948)	(7,181)
Balance at the end of the year	$ 16,586	$ 17,106

Intangible Assets and Contract

Intangible Assets and Contract Liabilities - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Intangible Assets
Intangibles assets, beginning balance	$ 681	$ 1,286
Amortization for the year	(303)	(605)
Intangibles assets, ending balance	378	681
Above Market Value Of Time Charter [Member] | Tordis Knutsen [Member]
Intangible Assets
Intangibles assets, beginning balance	305	608
Amortization for the year	(152)	(303)
Intangibles assets, ending balance	153	305
Above Market Value Of Time Charter [Member] | Vigdis Knutsen [Member]
Intangible Assets
Intangibles assets, beginning balance	376	678
Amortization for the year	(151)	(302)
Intangibles assets, ending balance	$ 225	$ 376

Intangible Assets and Contrac_2

Intangible Assets and Contract Liabilities - Additional information (Details) - USD ($) $ in Millions	1 Months Ended		6 Months Ended
	Aug. 31, 2011	Mar. 31, 2011	Jun. 30, 2021	Dec. 31, 2020
Intangible Assets
Accumulated amortization for contract liabilities			$ 15.3	$ 14.5
Recife Knutsen
Intangible Assets
Period for amortization of unfavorable contractual rights	12 years
Fortaleza Knutsen
Intangible Assets
Period for amortization of unfavorable contractual rights		12 years
Tordis Knutsen [Member] | Above Market Value Of Time Charter [Member]
Intangible Assets
Remaining term of the contract			4 years 9 months 18 days
Vigdis Knutsen [Member] | Above Market Value Of Time Charter [Member]
Intangible Assets
Remaining term of the contract			4 years 10 months 24 days

Intangible Assets and Contrac_3

Intangible Assets and Contract Liabilities - Summary of Estimated Future Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Estimated future amortization of intangible assets
Remainder of 2021	$ 303
2022	75
Total	$ 378	$ 681	$ 1,286

Intangible Assets and Contrac_4

Intangible Assets and Contract Liabilities - Schedule of Contract Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Contract liabilities:
Unfavorable contract rights, Beginning Balance	$ (3,686)	$ (5,203)
Amortization income	758	1,517
Unfavorable contract rights, Ending Balance	$ (2,928)	$ (3,686)

Intangible Assets and Contrac_5

Intangible Assets and Contract Liabilities - Amortization of Contract Liabilities Classified Under Time Charter and Bareboat Revenues (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Amortization of contract liabilities
Remainder of 2021	$ 759
2022	1,518
2023	651
Total	$ 2,928	$ 3,686	$ 5,203

Long-Term Debt - Components (De

Long-Term Debt - Components (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Long-Term Debt
Long-term debt	$ 1,003,211	$ 1,036,118
Less: current installments	353,643	186,723
Less: unamortized deferred loan issuance costs	2,273	2,535
Current portion of long-term debt	351,370	184,188
Amounts due after one year	649,568	849,395
Less: unamortized deferred loan issuance costs	3,220	3,238
Long-term debt, less current installments, and unamortized deferred loan issuance costs	646,348	846,157
$320 million loan facility
Long-Term Debt
Long-term debt	237,190	252,245
Debt instrument face amount	320,000	320,000
$55 million revolving credit facility
Long-Term Debt
Long-term debt	5,000	34,279
Debt instrument face amount	55,000	55,000
Hilda Loan Facility [Member]
Long-Term Debt
Long-term debt	75,385	78,462
Torill Loan Facility [Member]
Long-Term Debt
Long-term debt	78,333	81,667
$172.5 million loan facility
Long-Term Debt
Long-term debt	52,140	58,340
Debt instrument face amount	172,500	172,500
Raquel Loan Facility [Member]
Long-Term Debt
Long-term debt		52,725
Tordis Loan Facility [Member]
Long-Term Debt
Long-term debt	73,341	75,871
Vigdis Loan Facility [Member]
Long-Term Debt
Long-term debt	74,606	77,136
Lena Loan Facility [Member]
Long-Term Debt
Long-term debt	73,500	75,950
Brasil Loan Facility [Member]
Long-Term Debt
Long-term debt	47,855	50,997
Anna loan facility
Long-Term Debt
Long-term debt	60,157	62,196
Tove loan facility
Long-Term Debt
Long-term debt	84,066	86,250
$25 million revolving credit facility
Long-Term Debt
Debt instrument face amount	25,000
$25 million revolving credit facility | NTT
Long-Term Debt
Long-term debt	25,000	25,000
Debt instrument face amount	25,000	25,000
$25 million revolving credit facility | Shinsei
Long-Term Debt
Long-term debt	25,000	25,000
Debt instrument face amount	25,000	$ 25,000
Raquel Sale & Leaseback
Long-Term Debt
Long-term debt	$ 91,638

Long-Term Debt - Summary of Par

Long-Term Debt - Summary of Partnership's Outstanding Debt Repayable (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument, Redemption [Line Items]
Remaining 2021	$ 116,386
2022	311,817
2023	290,755
2024	141,822
2025	74,422
2026 and thereafter	68,009
Total	1,003,211	$ 1,036,118
Sale & Leaseback
Debt Instrument, Redemption [Line Items]
Remaining 2021	2,433
2022	4,960
2023	5,177
2024	5,418
2025	5,640
2026 and thereafter	68,009
Total	91,637
Periodic repayment
Debt Instrument, Redemption [Line Items]
Remaining 2021	43,142
2022	70,348
2023	54,672
2024	13,011
2025	3,276
Total	184,449
Balloon repayment
Debt Instrument, Redemption [Line Items]
Remaining 2021	70,811
2022	236,509
2023	230,906
2024	123,393
2025	65,506
Total	$ 727,125

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Details) $ in Millions	6 Months Ended
	Jun. 30, 2021USD ($)
Long-Term Debt
Outstanding debt	$ 1,003.2
Partnership's loan agreements | London Interbank Offered Rate (LIBOR) | Minimum [Member]
Long-Term Debt
Long-term debt, fixed margin percentage	1.75%
Partnership's loan agreements | London Interbank Offered Rate (LIBOR) | Maximum [Member]
Long-Term Debt
Long-term debt, fixed margin percentage	2.40%
$25 million revolving credit facility
Long-Term Debt
Debt instrument face amount	$ 25

Related Party Transactions - Re

Related Party Transactions - Related Party Costs and Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Related Party Transaction
Operating expenses from other related parties	$ 172	$ 66	$ 299	$ 229
Total expenses	(6,031)	(6,536)	(11,526)	(6,551)
KNOT Management
Related Party Transaction
Administration fee	379	244	666	474
KOAS [Member]
Related Party Transaction
Administration fee	201	165	$ 395	323
Margin rate on administration cost			5.00%
KOAS UK [Member]
Related Party Transaction
Administration fee	19	31	$ 37	61
Margin rate on administration cost			5.00%
KNOT [Member]
Related Party Transaction
Time charter income from KNOT	1,866	105	$ 1,866	4,883
Vessel operating expenses	5,000	4,392	7,752	6,856
Technical and operational management fee from KNOT to Vessels	2,106	1,703	4,214	3,406
Administration fee	$ 20	$ 40	$ 29	$ 85

Related Party Transactions - Sc

Related Party Transactions - Schedule of Dues Payables to Related Party (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Related Party Transaction
Drydocking supervision fee	$ 134	$ 47
KNOT [Member]
Related Party Transaction
Drydocking supervision fee	$ 134	$ 47

Related Party Transactions - Am

Related Party Transactions - Amounts Due from and Due to Related Parties (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Jun. 30, 2021
Related Party Transaction
Amount due from related parties	$ 5,726	$ 1,762
Amount due to related parties	$ (2,140)	(3,450)
Acquisitions from KNOT | Tove Knutsen
Related Party Transaction
Percentage of interest acquired	100.00%
KOAS [Member]
Related Party Transaction
Amount due from related parties	$ 170	55
Amount due to related parties	(1,596)	(2,489)
KNOT and affiliates
Related Party Transaction
Amount due from related parties	5,556	1,707
Amount due to related parties	(544)	$ (961)
KNOT and affiliates | Vigdis Knutsen [Member]
Related Party Transaction
Amount due from related parties	$ 3,600

Related Party Transactions - Tr

Related Party Transactions - Trade Accounts Payable (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Related Party Transaction
Trade accounts payables to related parties	$ 1,442	$ 2,206
KOAS [Member]
Related Party Transaction
Trade accounts payables to related parties	920	1,304
KNOT and affiliates
Related Party Transaction
Trade accounts payables to related parties	$ 522	$ 902

Related Party Transactions - Ot

Related Party Transactions - Other current assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Related Party Transaction [Line Items]
Other current assets from related parties	$ 1,246	$ 2,147
KOAS [Member]
Related Party Transaction [Line Items]
Trading balances	353	450
KNOT and affiliates
Related Party Transaction [Line Items]
Trading balances	$ 893	$ 1,697

Commitments and Contingencies -

Commitments and Contingencies - Assets Pledged, Claims and Legal Proceedings (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Commitments and Contingencies
Book value of assets pledged as security for long-term debt and interest rate swap obligations	$ 1,642,000,000	$ 1,709,000,000
Accrued claim	$ 0	$ 0

Commitments and Contingencies_2

Commitments and Contingencies - Insurance (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Dec. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Insurance Proceeds
Insurance coverage deductible amount per vessel		$ 150		$ 150
Deductible period under business interruption insurance				14 days
Period of coverage under business interruption insurance				180 days
Limit of protection and indemnity insurance for pollution, per vessel per incident		1,000,000		$ 1,000,000
Loss of hire insurance payments recorded as a component of total revenues		4,397		10,279
Net vessel operating expense		17,394	$ 13,112	35,954	$ 28,746
Windsor Knutsen
Insurance Proceeds
Deductible period under business interruption insurance	14 days
Recoveries for repairs		2,500		4,100
Loss of hire insurance payments recorded as a component of total revenues		3,700		8,700
Claimed insurance recoveries including vessel operating expense		4,000		4,000
Net vessel operating expense				100
Tove Knutsen
Insurance Proceeds
Recoveries for repairs		300		500
Loss of hire insurance payments recorded as a component of total revenues		700		1,500
Claimed insurance recoveries including vessel operating expense		400		400
Net vessel operating expense				100
Bodil Knutsen
Insurance Proceeds
Recoveries for repairs		$ 500		500
Claimed insurance recoveries including vessel operating expense				300
Net vessel operating expense				$ 200

Earnings per Unit and Cash Di_3

Earnings per Unit and Cash Distributions - Calculations of Basic and Diluted Earnings per Unit (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings per Unit and Cash Distributions
Net income (loss)	$ (10,925)	$ 21,683	$ 17,216	$ 15,544
Series A Preferred unitholders' interest in net income	1,759	1,800	3,559	3,600
Net income attributable to the unitholders of KNOT Offshore Partners LP	(12,684)	19,883	13,657	11,944
Less: Distributions	18,150	18,034	36,184	36,068
Under (over) distributed earnings	$ (30,834)	$ 1,849	$ (22,527)	$ (24,124)
Weighted average units outstanding (basic):
General Partner	615	615	615	615
Weighted average units outstanding (diluted):
General Partner	615	615	615	615
Earnings per unit (basic):
General Partner	$ (0.38)	$ 0.60	$ 0.41	$ 0.36
Earnings per unit (diluted):
General Partner	(0.38)	0.60	0.41	0.36
Cash distributions declared and paid in the period per unit	0.52	0.52	1.04	1.04
Subsequent event: Cash distributions declared and paid per unit relating to the period	$ 0.52	$ 0.52	$ 1.04	$ 1.04
Common Units
Earnings per Unit and Cash Distributions
Net income attributable to the unitholders of KNOT Offshore Partners LP	$ (12,451)	$ 19,515	$ 13,404	$ 11,723
Weighted average units outstanding (basic):
Weighted average units outstanding, basic	32,782	32,694	32,738	32,694
Weighted average units outstanding (diluted):
Weighted average units outstanding, diluted	36,619	36,596	36,594	36,648
Earnings per unit (basic):
Earnings per unit (basic)	$ (0.38)	$ 0.60	$ 0.41	$ 0.36
Earnings per unit (diluted):
Earnings per unit (diluted)	$ (0.38)	$ 0.58	$ 0.41	$ 0.36
Limited Partner [Member] | Common Units
Earnings per Unit and Cash Distributions
Under (over) distributed earnings	$ (30,268)	$ 1,815	$ (22,114)	$ (23,679)
General Partner Units
Earnings per Unit and Cash Distributions
Net income attributable to the unitholders of KNOT Offshore Partners LP	(233)	368	253	221
Under (over) distributed earnings	(566)	34	(413)	(445)
IDR Holders
Earnings per Unit and Cash Distributions
Net income (loss)	700	700	1,400	1,400
Less: Distributions	$ 700	$ 700	$ 1,400	$ 1,400

Earnings per Unit and Cash Di_4

Earnings per Unit and Cash Distributions - Additional Information (Details)	May 27, 2021shares	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2021shares
Distribution Made to Limited Partner
May 27, 2021: Conversion of Series A Preferred Units						(208,334)
Series A Preferred Stock
Distribution Made to Limited Partner
Potentially dilutive preferred units						3,541,666
IDR Holders | Maximum [Member]
Distribution Made to Limited Partner
Required percentage of operating surplus distribution		48.00%	48.00%	48.00%	48.00%
Common Units
Distribution Made to Limited Partner
May 27, 2021: Conversion of Series A Preferred Units						215,292
Common Units | Public
Distribution Made to Limited Partner
Number of common units and subordinated units outstanding						24,251,518
Common Units | KNOT [Member]
Distribution Made to Limited Partner
Number of common units and subordinated units outstanding						8,567,500
Tortoise Direct Opportunities Fund LP | Series A Preferred Stock
Distribution Made to Limited Partner
Shares held	416,677
Shares sold	208,333
May 27, 2021: Conversion of Series A Preferred Units	208,334
Tortoise Direct Opportunities Fund LP | Common Units
Distribution Made to Limited Partner
May 27, 2021: Conversion of Series A Preferred Units	215,292
Conversion rate	1.0334
Public | Partnership [Member]
Distribution Made to Limited Partner
Percentage of limited partner interest						73.70%
KNOT [Member] | Common Units | Series A Preferred Stock
Distribution Made to Limited Partner
May 27, 2021: Conversion of Series A Preferred Units						208,333
KNOT [Member] | Partnership [Member]
Distribution Made to Limited Partner
Percentage of limited partner interest						26.00%
KNOT [Member] | KNOT [Member]
Distribution Made to Limited Partner
Number of general partner units outstanding						615,117
KNOT [Member] | Common Units | KNOT [Member]
Distribution Made to Limited Partner
Number of common units and subordinated units outstanding						90,368
KNOT [Member] | Partnership [Member]
Distribution Made to Limited Partner
Percentage of limited partner interest						0.30%
Percentage of general partner interest						1.83%

Acquisitions - Purchase Price A

Acquisitions - Purchase Price Allocation (Details) - Tove Knutsen $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Acquisitions
Purchase consideration	$ 21,898
Less: Fair value of net assets acquired:
Vessels and equipment	117,978
Cash	804
Inventories	136
Derivatives assets (liabilities)	(3,537)
Others current assets	270
Long-term debt	(93,139)
Deferred debt issuance	769
Trade accounts payable	(430)
Accrued expenses	(622)
Amounts due to related parties	(331)
Subtotal	$ 21,898

Acquisitions - Purchase Conside

Acquisitions - Purchase Consideration (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Acquisitions
Allocation to drydocking included in property, plant and equipment	$ 3,040
Tove Knutsen
Acquisitions
Cash consideration paid to KNOT (from KNOP)	25,430
Purchase price adjustments	(3,596)
Acquisition-related costs	64
Purchase price	$ 21,898

Unit activity (Details)

Unit activity (Details)	May 27, 2021shares	Jun. 30, 2021shares
Limited Partners' Capital Account [Line Items]
May 27, 2021: Conversion of Series A Preferred Units		(208,334)
Convertible Preferred Units, Beginning balance		3,750,000
Convertible Preferred Units, End balance		3,541,666
General Partner Units
Limited Partners' Capital Account [Line Items]
Units, Beginning balance		615,117
Units, Ending balance		615,117
Common Units
Limited Partners' Capital Account [Line Items]
Units, Beginning balance		32,694,094
May 27, 2021: Conversion of Series A Preferred Units		215,292
Units, Ending balance		32,909,386
Tortoise Direct Opportunities Fund LP | Common Units
Limited Partners' Capital Account [Line Items]
May 27, 2021: Conversion of Series A Preferred Units	215,292
Conversion rate	1.0334
Tortoise Direct Opportunities Fund LP | Series A Convertible Preferred Units
Limited Partners' Capital Account [Line Items]
May 27, 2021: Conversion of Series A Preferred Units	208,334
Shares held	416,677
Shares sold	208,333

Trade Accounts Receivable and_3

Trade Accounts Receivable and Other Current Assets - Trade Accounts Receivable (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Trade Accounts Receivable and Other Current Assets
Provision for Doubtful Accounts	$ 0	$ 0

Trade Accounts Receivable and_4

Trade Accounts Receivable and Other Current Assets - Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Trade Accounts Receivable and Other Current Assets
Insurance claims for recoveries	$ 7,477
Refund of value added tax	1,762	$ 1,429
Prepaid expenses	1,392	1,050
Other receivables	3,750	3,032
Total other current assets	$ 14,381	$ 5,511

Write-Down of Long-Lived Asse_2

Write-Down of Long-Lived Assets (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021
Write-Down of Long-Lived Assets
Write-down related to vessel	$ 29,421	$ 29,421

Subsequent Events (Details)

Subsequent Events (Details) - Subsequent Event $ / shares in Units, $ in Millions	Aug. 26, 2021USD ($)	Aug. 25, 2021USD ($)installment	Aug. 12, 2021USD ($)$ / shares
Subsequent Events
Cash distributions paid in the period per unit | $ / shares			$ 0.52
$345 senior secured credit facility
Subsequent Events
Debt instrument face amount		$ 345
Number of quarterly installments | installment		20
Balloon payment to be paid		$ 219
$345 senior secured credit facility | London Interbank Offered Rate (LIBOR)
Subsequent Events
Interest margin percentage		2.05%
Series A Preferred Unit [Member]
Subsequent Events
Cash distributions			$ 1.7
Common Units | ATM
Subsequent Events
Issuance of common stock units	$ 100