increased professional services, $2.3 million in increased payroll expenses due to more headcount, and a $0.7 million increase in marketing expenses.
Transaction bonus
There was no transaction bonus awarded during the six months ended June 30, 2021. Transaction bonus for the six months ended June 30, 2020 was $5.3 million, which was awarded to certain eligible employees in conjunction with the LS Power acquisition of EVgo.
Depreciation, amortization and accretion
Depreciation, amortization and accretion expenses for the six months ended June 30, 2021 increased $0.5 million, or 11%, to $5.1 million compared to $4.6 million for the six months ended June 30, 2020. The increase was primarily due to additional amortization expense recognized as a result of the LS Power acquisition of EVgo.
Operating loss and operating margin
During the six months ended June 30, 2021, EVgo had an operating loss of $33.7 million, an increase of $4.7 million, or 16%, compared to $29.0 million for the six months ended June 30, 2020. Operating margin for the six months ended June 30, 2021 improved to negative 379% compared to negative 426% for the six months ended June 30, 2020. The improvement in operating margin period-over-period was primarily due to the leveraging of increased revenue.
Interest expense, related party
Interest expense, related party, for the six months ended June 30, 2021 increased $1.5 million, or 376%, to $1.9 million compared to $0.4 million for the six months ended June 30, 2020. The increase was related to increased borrowings under the LS Power Note entered into in January 2020.
Other income, related party
There was no other income, related party, for the six months ended June 30, 2021 compared to $0.3 million for the six months ended June 30, 2020. The decrease was due to the reclassification of reimbursements received under the NRG Agreement and NEDO Agreement to other income, net, as a result of the LS Power Merger. Following the close of the merger, these entities were no longer related parties.
Other income, net
Other income, net, for the six months ended June 30, 2021 decreased $3.2 million, or 84%, to $0.6 million compared to $3.9 million for the six months ended June 30, 2020. The decrease was primarily due to the decrease in income from one of the capital build programs that ended during 2020.
Net loss
Net loss for the six months ended June 30, 2021 was $35.0 million, a $9.8 million, or 39%, increase compared to $25.2 million for the six months ended June 30, 2020. The increased net loss was primarily due to the increased general and administrative expenses, and, to a lesser extent, the decrease in other income, net, partially offset by the impact of the transaction bonus that was incurred during the six months ended June 30, 2020.
Non-GAAP Financial Measures
This Amended Super 8-K includes the non-GAAP financial measures: “Adjusted Cost of Sales,” “Adjusted Gross Profit (Loss),” “Adjusted Gross Margin,” “EBITDA,” “Adjusted EBITDA” and “Receipts.” EVgo believes these financial measures are useful to investors in evaluating EVgo’s financial performance. In addition, EVgo uses these measures internally to establish forecasts, budgets, and operational goals to manage and monitor its business. Further, due to the