4.  Customer Concentrations and Accounts Receivable

RSP Systems, Capstone Engineered Solutions, Cal Microturbine, and Horizon Power Systems, four of the Company’s domestic distributors, accounted for 15%, 13%, 12%, and 10% of revenue for the three months ended September 30, 2022, respectively. E-Finity Distributed Generation, LLC (“E-Finity), one of the Company’s domestic distributors, and Optimal Group Australia Pty Ltd (“Optimal”), one of the Company’s international distributors, accounted for 23% and 11% of revenue for the three months ended September 30, 2021, respectively. Cal Microturbine accounted for 18% of revenue for the six months ended September 30, 2022. E-Finity and Optimal accounted for 17% and 10% of revenue for the six months ended September 30, 2021, respectively.

Additionally, E-Finity accounted for 11% of net accounts receivable as of September 30, 2022. E-Finity accounted for 28% of net accounts receivable as of March 31, 2022. The Company recorded a net bad debt expense of $0.1 million during the three and six months ended September 30, 2022. The Company recorded a net bad debt expense of zero during three and six months ended September 30, 2021.