4.  Customer Concentrations and Accounts Receivable

Accounts receivables are presented on the Condensed Consolidated Balance Sheets, net of estimated credit losses. The carrying amounts of trade accounts receivable represent the maximum credit risk exposure of these assets. On a quarterly basis, in accordance with ASC 326, the Company evaluates the collectability of outstanding accounts receivable balances to determine an allowance for credit loss that reflects its best estimate of the lifetime expected credit losses. The Company evaluated its current estimate of expected credit losses and determined that there was no significant change. It took into account certain economic factors in calculating the risk factors used to determine the CECL historical loss rate for each aging bucket. Additionally, the Company analyzed the risk of our receivables using geography and other customer circumstances to determine its allowance for credit risk. Changes in the CECL allowance for accounts receivable are as follows (in thousands):

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Horizon Power Systems (“Horizon”) and E-Finity Distributed Generation (“E-Finity”), two of the Company’s domestic distributors and Optimal Group Australia Pty Ltd (“Optimal”), one of the Company’s international distributors, accounted for 15%, 10% and 13% of revenue for the three months ended June 30, 2023, respectively. Cal Microturbine and E-Finity Distributed Generation, LLC (“E-Finity”), two of the Company’s domestic distributors accounted for 24% and 11%, of revenue for the three months ended June 30, 2022, respectively.

Additionally, Horizon and Cal Microturbine accounted for 12% and 10% of net accounts receivable as of June 30, 2023, respectively. E-Finity accounted for 12% of net accounts receivable as of March 31, 2023. The Company did not have a credit loss expense during the three months ended June 30, 2023 and 2022.