For the six months ended June 30, 2023 and 2022, Bitcoin Mining revenue was $97.8 million, and $104.1 million, respectively. The decrease of $6.3 million was primarily due to lower Bitcoin values in the 2023 period, averaging $25,132 per coin, as compared to $37,177 for the 2022 period. This was partially offset by an increase of 1,090 Bitcoin mined in the 2023 period as compared to the 2022 period. Additionally, the Company continued its effective employment of its proprietary power strategy to significantly reduce overall power costs. As noted below, during the six months ended June 30, 2023, the Company earned $16.5 million in power credits, which were received in cash or credited against its power invoices, as a result of temporarily pausing its operations. The power credits equate to approximately 658 Bitcoin, as computed using the average daily Bitcoin prices for the 2023 period. During the six months ended June 30, 2022, the Company earned $8.3 million in power credits, or the equivalent of approximately 222 Bitcoin.
For the six months ended June 30, 2023 and 2022, Data Center Hosting revenue was $16.7 million, and $19.5 million, respectively. The decrease of $2.8 million was primarily due to lower revenue share from customers due to the lower Bitcoin values in the 2023 period, as noted above, combined with hosting fewer customers during 2023.
For the six months ended June 30, 2023 and 2022, Engineering revenue was $35.5 million and $29.1 million, respectively. The increase of $6.4 million was primarily attributable to an increase in data center development across the country. Our custom electrical products such as switchgear and power distribution centers are used as important components in data center development and there has been increased demand for these products due to the continued increase in data center construction by developers.
Costs and expenses
Cost of revenues for Bitcoin Mining for the six months ended June 30, 2023 and 2022, was $45.5 million and $37.1 million, respectively, an increase of approximately $8.5 million. As a percentage of Bitcoin Mining revenue, cost of revenues totaled 46.6% and 35.6% for the six months ended June 30, 2023 and 2022, respectively. Cost of revenues consists primarily of direct production costs of Bitcoin mining operations, including electricity, labor, and insurance, but excluding depreciation and amortization, which are separately stated. The increase was primarily due to the increase in Bitcoin mining capacity at the Rockdale Facility, which requires more headcount and direct costs necessary to maintain and support the Bitcoin mining operations. As noted below, during the six months ended June 30, 2023 and 2022, the Company earned $16.5 million and $8.3 million, respectively, in power credits to be credited against its power invoices, as a result of temporarily pausing its operations. These credits are recognized in power curtailment credits in the statements of operations, outside of cost of revenues, but significantly reduce the Company’s overall cost to mine Bitcoin. When netting the power curtailment credits with the costs of revenues, the net costs as a percentage of Bitcoin Mining revenue were 35.8% and 32.9% for the six months ended June 30, 2023 and 2022, respectively.
Cost of revenues for Data Center Hosting for the six months ended June 30, 2023 and 2022, was $47.8 million and $30.2 million, respectively, an increase of approximately $17.6 million. The costs consisted primarily of direct power costs, with the balance primarily incurred for rent and compensation costs. The increase was primarily attributable to the significant increase in size of our Rockdale Facility over the period, which has more than doubled since 2021.
Cost of revenues for Engineering for the six months ended June 30, 2023 and 2022, was $33.7 million and $26.7 million, respectively, an increase of approximately $7.0 million. The costs consisted primarily of direct materials and labor, as well as indirect manufacturing costs. The increase was primarily due to an increase in materials purchased, as well as additional labor required to support increased demand for our custom electric products from data center developers. Increased competition for direct materials due to supply chain constraints contributed to additional costs, as well as inflationary pressure for labor in manufacturing.
Selling, general and administrative expenses for the six months ended June 30, 2023 and 2022, were $32.5 million and $21.5 million, respectively, an increase of approximately $11.0 million. Selling, general and administrative expenses consist of stock-based compensation, legal and professional fees and other personnel and related costs. The increase was primarily due to increases in compensation expenses of $5.7 million as a result of hiring additional employees to support the Company’s ongoing growth, increased professional fees of $3.9 million primarily related to public company compliance and information technology projects, and increases of $4.0 million in other general operating costs to support the Company’s growth, partially offset by decreased stock compensation expenses of $2.6 million, primarily attributable to increased forfeitures of awards in the 2023 period as compared to the 2022 period.
Depreciation and amortization expense for the six months ended June 30, 2023 and 2022, was $125.5 million and $34.8 million, respectively, an increase of approximately $90.7 million. The increase was primarily due to higher depreciation expense recognized for the Rockdale Facility and significant increase in number of recently acquired miners.