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ENERGY STORAGE SYSTEMS, NET
9 Months Ended
Sep. 30, 2021
Property, Plant and Equipment [Abstract]  
ENERGY STORAGE SYSTEMS, NET ENERGY STORAGE SYSTEMS, NET
Energy Storage Systems, Net
Energy storage systems, net, consists of the following (in thousands):
September 30, 2021
Energy storage systems placed into service$143,423 
Less: accumulated depreciation(42,465)
Energy storage systems not yet placed into service13,191 
Total energy storage systems, net$114,149 
Depreciation expense for energy storage systems was approximately $3.6 million and $3.6 million for the three months ended September 30, 2021 and 2020, respectively. Depreciation expense for energy storage systems was approximately $10.8 million and $10.3 million for the nine months ended September 30, 2021 and 2020, respectively. Depreciation expense is recognized in cost of service revenue.