iSun (ISUNQ) 8-K Regulation FD Disclosure

Exhibit 99.1

 Nasdaq: ISUN www.isunenergy.com    Q3 2021 

 This presentation contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of1995. These forward-looking statements include, but are not limited to, statements about (i) iSun’s plans, objectives, expectations and intentions and other statements contained in this presentation that are not historical facts; and (ii) other statements identified by words such as “expects” “anticipates,” “intends,” “plans,” “believes,” “seeks,” “estimates,” “targets,” “projects,” or words of similar meaning generally intended to identify forward-looking statements. These forward- looking statements are based upon the current beliefs and expectations of the respective management of iSun and are inherently subject to significant business, economic and competitive uncertainties and contingencies, many of which are beyond the control of iSun. In addition, these forward-looking statements are subject to assumptions with respect to future business strategies and decisions that are subject to change. Actual results may differ materially from the anticipated results discussed in these forward-looking statements because of possible uncertainties. 

 US Solar Market  “The electrification of almost everything is coming, and we’re just not ready for it.”Wall Street Journal, May 21, 2021  By 2031, the U.S. must install more solar annually than has what been installed cumulatively through 2020.1 Automotive electrification and a retreat from coal and fossil fuels further compounds the need to accelerate the adoption of renewable energy, particularly solar.$22.9BSolar Market in 20252  $147BEV Sales in 20283  $0  GM’s non-EV sales in 203541: https://www.seia.org/solar-industry-research-data2: https://linchpinseo.com/trends-solar-energy-industry/3: https://www.grandviewresearch.com/industry-analysis/north-america-electric-vehicles-market4: https://www.nytimes.com/2021/01/28/business/gm-zero-emission-vehicles.html 

 History repeats itself  https://www.modernpowersystems.com/features/featureamory-lovins-and-the-soft-path-40-years-on-5652985/      Spot the car  Spot the horse  1900Easter: NYC 5th Ave  Source: US National Archives  Source: George Grantham Bain Collection  1913Easter: NYC 5th Ave 

 Why iSunFor 50 years, iSun has enabled the important transitions of our world by accelerating the adoption of proven, technological innovations that improve our lives.  “Today, iSun believes that clean, renewable, solar energy is the most important investment we can make. We are driven to use our capabilities to accelerate the transition from dirty to clean energy.”Jeffrey PeckCEO & Chairman of the Board      1972Company founded and rooted in large, complex electrical construction projects in innovative markets.        1979Built IBM’s clean rooms for silicon chip fabrication        1984Added data and telecommunication installation services      2009Added solar installation services, first in Industrial, Commercial, then Residential and Utility segments.      2019Listed on Nasdaq as PECK via SPAC to execute its growth planSuccessfully deSPACed and trading as ISUN      2021Fully integrated platform solar EPC; servicing Residential, Commercial,Industrial, Utility and EV markets 

 Positioned to AccelerateiSun has unmatched experience and capabilities to develop and construct solar projects across all solar market sectors and expects that electric vehicle adoption will be a gateway to accelerating the renewable energy transition in each solar market sector.  RESIDENTIAL SOLAREV purchases with at-home charging promotes residential solar + storageinstallation and other smart home energy upgrades  COMMERCIAL SOLAREV fleet and workplace charging adoption by businesses promotessolar projects at work and at employee homes to future-proofs costs  UTILITY SOLARIncreased local electricity demand promotes the need for utility scale solarprojects and infrastructure upgrades to meet demand  INDUSTRIAL & MUNICIPAL SOLARIncreased adoption, demand charges and infrastructure electrification results in resilient microgrid and community solar projects   

   Capabilities Add ValueiSun is the only publicly listed Solar Engineering, Procurement and Construction (EPC) contractor with capabilities across the entire solar scale continuum, including solar EV charging.  RESIDENTIAL SOLARSolar, storage, service, smart home  COMMERCIAL SOLARSolar, electrical, data,O&M services  UTILITY SOLARSolar Development and Construction Services  INDUSTRIAL & MUNICIPAL SOLARSolar, smart city, microgrid, community solar 

           Connections Accelerate GrowthiSun’s ability to connect the optimal attributes from one market sector into other market sectors is a key value proposition that accelerates growth across all market sectors.  Owning the residential customer relationship offers multiple sales opportunities over yearslowering overall customer acquisition costsmaximizing lifetime customer revenue  Resell, Upsell, and Cross-sell to and from residential, commercial and industrial customers increases revenue without added marketing cost  Utility scale economies for purchasing can be leveraged across industrial, commercial and residential projects  EV charging is a conversation starter, a necessary value-add across all market sectors and a visual representation of values 

 Growth Strategy  iSun’s three-pronged growth strategy leverages the multiple connections across market sectors and de-risks the entry into new markets – any one market sector opens the door to other market sectors    2021Presence  States with existing projects under contract provide rationale for near- term expansion in these states and into neighboring regions  2022Opportunities  States with significant project opportunities(e.g. Hartsel, CO 100MW)provide rationale for future expansion contingent on project milestones  Expansion Options  States where new opportunities may provide a rational for expansion for any or all market segments    States with existing solar EV charging presence that may provide rationale for market expansion      Organic GrowthExpand relationships with customers for solar EPC opportunities across theEastern United States and other markets      M&A and Strategic InvestmentsAcquisitions of electrical and solar EPC companies; investment in companies that increase EPC pipeline opportunities      Solar Energy Asset OwnershipInvest in solar energy assets to provide recurring revenue and cash flow to offset operating costs for margin enhancement  Solar Power World 2020 Ranking1st Solar Contractor in VT3rd C&I EPC Contractor in USA 22nd EPC Contractor in USA 38th Solar Contractor in USA 

 Growth TacticsiSun takes a rational approach to growth with its three-pronged strategy in each market sector.    Organic Growth    M&A and Strategic Investments    Solar Energy Asset Ownership  >Super-regional: East Coast expansion>Outbound sales and marketing + referrals for low customer acquisition cost and maximum lifetime customer revenue from upsell, resell, and cross-sell opportunities.  >Platform roll-up targeting $5-50M revenue + profitable, outstanding operators, local brand, high growth market, customer retention, services include solar, storage, community programs, O&M, other  >Opportunities to finance residential/commercial solar leases (PPA+/- asset ownership), and solar loans  >Opportunistic expansion across the Northeast and other states based onreferrals and existing customers or fromnew opportunities created by outbound sales activities of the residential, commercial, utility or solar EV charging business  >Targeting $1-10M revenue + profitable electrical contractors with licensed electricians but without solar experience, geographically located in areas of existing or planned solar EPC contracts.  >Seeking Pre-NTP, NTP, or post-COD projects with minimum 12% unlevered IRR.>On Balance sheet up to 30MW or until recurring cashflow pays for iSun OpEx  >Unconstrained geographically but prioritized by paid development services contract location.>Outbound sales and marketing to developers, utilities, and asset owners>Preference to “build-operate-transfer”projects directly for utilities  >In-sourced staffing minimizes OpEx>Subcontracted construction labor>No active M&A program  >Finance partnerships provide off- balance sheet project finance to fund EPC contracts and/or minority solar asset ownership. (e.g. Fusion Renewable andGreenSeed Investors / Solar Project Partners)    Residential SolarCommercial Solar    Industrial & Municipal Solar    Utility Solar 

 Residential & CommercialiSun has installed nearly 3,000 residential solar projects since 2012 and is executing a platform roll-up strategy to create a market leader; iSun Residential.  2021 M&A Targets$75MResidential & Commercial Revenue from Targets75MWTotal Residential Systems Installed by Targets7,500Total Residential Customers Served by Targets  $5-50M revenue + profitableEast Coast USAResidential and CommercialOutstanding operatorsStrong local brand reputationUltra-high-touch, long-term customer relationshipsLow-cost customer acquisitionServices include solar, storage,community programs, O&M, other  East Coast M&A Target Profile 

 iSun Residential project examples 

 iSun Commercial project examples 

 Industrial & MunicipaliSun has served its industrial and municipal solar, data and electric EPC customers for decades by consistently delivering value and results for large, complex projects.  $40MEst. iSun, Inc. Revenue Solar, Data, Electric200MWTotal iSun, Inc. Solar Systems Installed$76.8MCurrent Backlog            solar  dataelectric  Referral Network M&A Target Profile 2021 Goals  $1-10M revenue + profitableElectrical contractors withlicensed electricians but without solar experienceGeographically located in areas of existing or planned solar EPC contracts  Revenue mix 

 iSun Industrial & Municipal project examples 

 UtilityiSun Utility delivers solar development and construction services to asset owners and developers, and also targets “build-operate-transfer” projects directly for utilities  $69BUtility project opportunity  213MWTotal Utility Systems Installed via OCS Acquisition5GW  Projects under reviewiSun Utility can originate land, rapidly diligence project sites, vet technical feasibility, execute internal engineering packages on a turnkey basis and run project finance processes… then build it  Internal ProjectsAcceleration and cost reduction of iSun owned-operated assets (Ex: community solar projects in synergy with iSun Residential)  Third Party ServicesSupport third parties early in the project lifecycle and gain captive rights to EPC (Ex: $120 million Fusion Bishop Portfolio)  EPC ContractsReduce costs and move projects more quickly through pipeline, offer added value to clients by in-sourcing engineering (Ex: New Hampshire GSSG Portfolio)  iSun Utility Takes Projects from Land Control to Ready for Construction 

 Utility Case Study<30 days after launch, iSun Utility closed agreements on 118 megawatt Bishop Portfolio, financed by Israeli public companies Alon Gas and Modiin; portfolio originally developed by Fusion Renewables  iSun Utility selected for both development and construction services  Up to $120 Million EPC Services RightsEngineering, Procurement and Construction service contracts for up to 8 sitesExpected margin : 10% margin plus 8% overhead  $1.25 Million Development Service ContractOverseeing land control, site vetting, interconnection, engineering, project finance and moreExpected margin: 30 – 50% 

 iSun Utility completed project examples 

 Solar EV ProductsiSun solar EV products are gateways to more solar EPC opportunities and allow iSun to provide customized solutions for customers across all market sectors.  Bifacial solar panels  Bifacial solar panels 

 iSun solar EV products project examples – solar EV charging & solar bench 

 iSun InnovationiSun invests in innovative companies that drive growth opportunities to iSun for each market sector  iSun investment rationale  AmpUp is the software backbone of the iSunOS with leading edge patented technology for the best charging user experience for iSun customers  Exclusive EV membership for gig drivers. The most affordable all-in-one way to gig electric.  AmpUp is an electric vehicle (EV) software company and network provider that enables drivers, hosts, and fleets to chargestress-free.  www.ampup.io  www.drivehive.com  iSun investment rationale  DriveHive bundles the EV with charging, and iSun’s solar EV charging solution is ideal for rapid deployment of charge sites on-grid or off-grid  iSun investment rationale  iSun has the right to construct all solar projects, financing is off- balance sheet, and iSun is an owner in all assets constructed through Solar Project Partners LLC  GreenBond Advisors delivers financial product innovation into the Green Bond market with new Green Bond products that enable risk-averse investment capital to support renewable energy infrastructure development.  www.greenbondadvisors.com 

 Recurring revenue drives marginiSun owns 6 megawatts of solar assets with a goal to reach 50 megawatts by 2023 in order to offset operating expenses with recurring revenue, which directly enhances net margins.  6MW2021 solar assets  $500k2021 recurring cashflow  50MWEst. 2023 solar assets  $4MEst. 2023 recurring cashflow     

 FinancialsiSun has the necessary access to capital to fund its profitable growth strategy  $39.5M(ATM: B.Riley)      ACCESS TO CAPITAL  WORKING CAPITAL  est. 2021 REVENUEiSun, Inc.: Solar, Data, Electric  $40M  $76.8M  $21.8M  CURRENT BACKLOG 

 Market Comparison  Market analysis indicates that iSun is both a growth and value opportunity across all sectorsResidential Solar  Market data as of July 29, 2021; Market Capitalization reflects 9.08M shares outstanding; Financial metrics as of 2Q 2021 unless otherwise noted1 Based on proposed post de-SPAC share count Source: Capital IQ and investor presentations Date: As of market close on 06/23/20.  ($ in millions except per share amounts)Share Price Market Enterprise EV / Revenue EV / EBITDA Installed # of Company Name Current Capitalization Value FY2020 FY2021 FY2022 FY2023 FY2020 FY2021 FY2022 FY2023 MW Customers                              Sunrun Inc., (NasdaqGS:RUN)  $52.62  $10,730.8  $17,147.6  NM  11.6x  10.1x  8.9x  NM  NM  NM  319.9x  3,000  573,000    Sunnova Energy International Inc., (NYSE:NOVA)  $36.72  $4,112.1  $6,810.4  41.0x  30.0x  20.1x  15.4x  110.6x  82.4x  45.9x  30.5x  861  116,400    Sunworks, Inc., (NasdaqCM:SUNW)  $8.68  $234.8  $155.9  NM  1.2x  0.9x  NM  NM  NM  311.9x  NM  -  -    Sunlight Financial Holdings Inc., (NYSE:SUNL)  $7.96  $675.3  $1,412.1  20.5x  11.5x  9.0x  7.1x  56.5x  23.5x  17.2x  12.6x  - -      Average 30.8x 13.6x 10.0x 10.4x 83.6x 53.0x 125.0x 121.0xMedian 30.8x 11.5x 9.6x 8.9x 83.6x 53.0x 45.9x 30.5x                            iSun, Inc., (NasdaqCM:ISUN)  $9.16  $83.2  $68.7  3.9x  1.5x  0.8x  NM  NM  56.3x  10.9x  NM  400  3,000  Average 4.5x 3.7x 3.1x 2.7x 57.6x 27.1x 20.6x 16.9xMedian 4.0x 3.4x 2.9x 2.6x 45.7x 33.1x 25.3x 20.7x                            iSun, Inc., (NasdaqCM:ISUN)  $9.16  $83.2  $68.7  3.9x  1.5x  0.8x  NM  NM  56.3x  10.9x  NM  400  3,000  Average 2.9x 1.9x 1.2x 1.1x 4.9x 7.1x 11.5x 8.1xMedian 2.5x 1.9x 1.2x 1.3x 12.0x 10.2x 12.6x 7.8x                            iSun, Inc., (NasdaqCM:ISUN)  $9.16  $83.2  $68.7  3.9x  1.5x  0.8x  NM  NM  56.3x  10.9x  NM  400  3,000  Average 79.6x 41.3x 18.0x 9.1x (141.4x) (55.1x) (221.5x) 104.2xMedian 61.1x 36.5x 12.2x 5.8x (84.3x) (40.7x) (38.4x) 33.6x                            iSun, Inc., (NasdaqCM:ISUN)  $9.16  $83.2  $68.7  3.9x  1.5x  0.8x  NM  NM  56.3x  10.9x  NM  400  3,000  Commercial & Industrial Solar  ---  ($ in millions except per share amounts)Share Price Market Enterprise EV / Revenue EV / EBITDA Installed # of                                              Company Name  Current  Capitalization  Value    FY2020    FY2021    FY2022    FY2023    FY2020  FY2021    FY2022    FY2023  MW    Customers    Ameresco, Inc., (NYSE:AMRC)  $68.02  $3,487.4    $4,311.9    4.4x    3.8x    3.4x    3.1x  37.7x    29.9x    25.6x  22.1x    -      SunPower Corporation, (NasdaqGS:SPWR)  $24.63  $4,249.2    $4,434.6    3.7x    3.0x    2.4x    2.1x  134.0x    36.2x    25.1x  20.3x  1,120    363,000    SolarEdge Technologies, Inc., (NasdaqGS:SEDG)  $261.13  $13,572.5    $13,103.0    9.0x    6.9x    5.5x    4.6x  53.6x    37.5x    27.3x  21.0x  24,000        Electricité de France S.A., (ENXTPA:EDF)  $12.43  $39,256.0    $96,605.0    1.1x    1.1x    1.1x    1.1x  5.0x    4.6x    4.4x  4.1x    -      Utility Solar  ($ in millions except per share amounts)Share Price Market Enterprise EV / Revenue EV / EBITDA                                     Company Name  Current  Capitalization  Value    FY2020    FY2021    FY2022    FY2023    FY2020  FY2021  FY2022    FY2023  FTC Solar, Inc., (NasdaqGM:FTCI)  $10.56  $890.2    $884.9    NM    2.9x    1.7x    1.3x  NM  NM    13.8x  7.8x  Array Technologies, Inc., (NasdaqGM:ARRY)  $13.61  $1,728.4    $2,117.6    2.5x    2.1x    1.8x    1.6x  13.3x  22.9x    14.2x  10.0x  Canadian Solar Inc., (NasdaqGS:CSIQ)  $40.71  $2,442.5    $3,968.3    1.2x    0.7x    0.6x    0.6x  12.0x  10.2x    6.7x  6.5x  Orbital Energy Group, Inc., (NasdaqCM:OEG)  $3.45  $221.2    $221.0    4.9x    1.8x    0.8x    NM  (10.6x)  (11.9x)    11.4x  NM  EV Charging  ($ in millions except per share amounts)Share Price Market Enterprise EV / Revenue EV / EBITDA                               Company Name  Current  Capitalization  Value    FY2020  FY2021  FY2022    FY2023    FY2020  FY2021  FY2022  FY2023  Beam Global, (NasdaqCM:BEEM)  $30.29  $269.2    $243.4  43.5x  21.8x    10.9x    5.8x  (67.3x)  NM  NM  152.1x  Blink Charging Co., (NasdaqCM:BLNK)  $34.05  $1,435.4    $1,206.1  217.0x  104.8x    44.7x    21.8x  (101.4x)  (41.9x)  (51.5x)  (54.8x)  ChargePoint Holdings, Inc., (NYSE:CHPT)  $24.07  $7,738.6    $7,154.2  NM  51.6x    34.9x    20.9x  NM  (66.7x)  (46.8x)  (60.4x)  EVBox1  $12.15  $1,701.0    $1,354.0  19.3x  11.3x    6.0x    3.6x  NM  (16.9x)  (30.1x)  677.0x  EVgo, Inc., (NasdaqGS:EVGO)  $11.95  $821.4    $854.8  61.1x  42.7x    15.8x    5.1x  (29.5x)  (14.7x)  (19.9x)  171.0x  Fastned B.V., (ENXTAM:FAST)  $68.00  $1,016.4    $1,086.9  148.1x  71.5x    24.2x    12.2x  (444.3x)  (175.5x)  178.8x  33.6x  Tritium1  $9.88  $1,682.6    $1,072.6  18.2x  12.8x    6.3x    3.0x  NM  (28.2x)  (59.6x)  15.1x  Volta1  $9.92  $2,014.8    $1,714.8  68.6x  36.5x    12.2x    6.1x  (59.1x)  (57.2x)  (1714.8x)  52.0x  Wallbox1  $9.93  $1,775.5    $1,465.5  61.1x  18.6x    6.5x    3.2x  (146.5x)  (39.6x)  (28.2x)  (47.3x) 

 Leadership  Management successfully deSPACed iSun and is delivering growth and value  Executive Leadership  Jeffrey PeckChairman andChief Executive Officer  John SullivanChief Financial Officer  Frederick (Kip) Myrick Executive Vice President, Residential, Commercial & Industrial SolarBoard of Directors  Michael d’AmatoChief Strategy Officer  Independent Directors  Andy MatthyIndependent Director  Claudia MeerIndependent Director  Stewart MartinIndependent Director  150Outstanding employees that deliver quality to iSun customers every day  Divisional Leadership  Daniel DusPresident, iSun Utility 

 ir@isunenergy.com