SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
Mar. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements of the Company have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim reporting and with the instructions to Form 10-Q and Article 10 of Regulation S-X, assuming the Company will continue as a going concern. Accordingly, the condensed consolidated balance sheet at December 31, 2022 has been derived from the audited financial statements at that date, but certain notes or other information that are normally required by GAAP have been omitted if they substantially duplicate the disclosures contained in the Company’s annual audited consolidated financial statements. In the opinion of Stem management, all normal and recurring adjustments considered necessary for a fair statement of the results for the interim period presented have been included in the accompanying unaudited condensed consolidated financial statements. These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2022. Operating results for the three months ended March 31, 2023 are not necessarily indicative of the results that may be expected for the year ending December 31, 2023 or for any other future interim period or year.
Principles of Consolidation	Principles of ConsolidationThe unaudited condensed consolidated financial statements include the accounts of the Company, its wholly-owned subsidiaries, and consolidated variable interest entities (“VIEs”). The Company presents non-controlling interests within the equity section of its condensed consolidated balance sheets, and the amount of consolidated net loss that is attributable to Stem and the non-controlling interest in its condensed consolidated statements of operations. All intercompany balances and transactions have been eliminated in consolidation.
Variable Interest Entities	Variable Interest Entities The Company forms special purpose entities (“SPEs”), some of which are VIEs, with its investors in the ordinary course of business to facilitate the funding and monetization of its energy storage systems. A legal entity is considered a VIE if it has either a total equity investment that is insufficient to finance its operations without additional subordinated financial support or whose equity holders lack the characteristics of a controlling financial interest. The Company’s variable interests arise from contractual, ownership, or other monetary interests in the entity. The typical condition for a controlling financial interest ownership is holding a majority of the voting interests of an entity; however, a controlling financial interest may also exist in entities, such as VIEs, through arrangements that do not involve controlling voting interests. The Company consolidates a VIE if it is deemed to be the primary beneficiary. The Company determines it is the primary beneficiary if it has the power to direct the activities that most significantly impact the VIEs’ economic performance and has the obligation to absorb losses or has the right to receive benefits of the VIE that could potentially be significant to the VIE. The Company evaluates its relationships with its VIEs on an ongoing basis to determine whether it is the primary beneficiary. Beginning in January 2022, the Company formed DevCo JVs with the purpose of originating potential battery storage facility projects in the specific locations and conducting early-stage planning and development activities. The Company determined that the DevCo JVs are VIEs as they lack sufficient equity to finance their activities without additional financial support. The Company determined that it has both (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance, and (2) the obligation to absorb losses or receive benefits from the VIE that could potentially be significant. Accordingly, the Company has determined that it is the primary beneficiary of the DevCo JVs, and as a result, the DevCo JVs’ operating results, assets and liabilities are consolidated by the Company, with third party minority owners’ share presented as noncontrolling interest. The Company applied the hypothetical liquidation at book value method in allocating recorded net income (loss) to each owner based on the change in the reporting period, of the amount of net assets of the entity to which each owner would be entitled to under the governing contracts in a liquidation scenario.
Reclassifications	ReclassificationsCertain prior year amounts have been reclassified for consistency with the current year presentation. Such reclassifications have no impact on previously reported net (loss) income, stockholders’ equity, or cash flows.
Use of Estimates	Use of Estimates The preparation of unaudited condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the unaudited condensed consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. The Company bases its estimates on historical experience and on various other assumptions believed to be reasonable. Actual results could differ from those estimates and such differences could be material to the financial position and results of operations. Significant estimates and assumptions reflected in these unaudited condensed consolidated financial statements include, but are not limited to, depreciable life of energy storage systems; the amortization of acquired intangibles; the amortization of financing obligations; deferred commissions and contract fulfillment costs; the valuation of energy storage systems, internally developed software, and asset retirement obligations; and the fair value of equity instruments, equity-based instruments, warrant liabilities, embedded derivatives and net assets acquired in a business combination.
Segment Information	Segment InformationOperating segments are defined as components of an entity for which discrete financial information is available that is regularly reviewed by the Chief Operating Decision Maker (“CODM”) in deciding how to allocate resources to an individual segment and in assessing performance. The Company’s Chief Executive Officer is the CODM. The CODM reviews financial information presented on a consolidated basis for purposes of making operating decisions, allocating resources, and evaluating financial performance. As such, management has determined that the Company operates as one operating segment that is focused exclusively on innovative technology services that transform the way energy is distributed and consumed. The operations acquired as part of the acquisition of AlsoEnergy have been included in the Company’s operating segment.
Concentration of Credit Risk and Other Uncertainties	Concentration of Credit Risk and Other Uncertainties Financial instruments that potentially subject the Company to concentration of credit risk consist of cash and cash equivalents and accounts receivable. The Company’s cash balances are primarily invested in money market funds or on deposit at high credit quality financial institutions in the U.S. The Company’s cash and cash equivalents are held at financial institutions where account balances may at times exceed federally insured limits. Management believes the Company is not exposed to significant credit risk due to the financial strength of the depository institution in which the cash is held. The Company has no financial instruments with off-balance sheet risk of loss. At times, the Company may be subject to a concentration of credit risk in relation to certain customers due to the purchase of large energy storage systems made by such customers. The Company routinely assesses the creditworthiness of its customers. The Company has not experienced material losses related to receivables from individual customers, or groups of customers during the three months ended March 31, 2023 and 2022. The Company does not require collateral. Due to these factors, no additional credit risk beyond amounts provided for credit losses is believed by management to be probable in the Company’s accounts receivable.
Significant Customers	Significant CustomersA significant customer represents 10% or more of the Company’s total revenue or accounts receivable, net balance at each reporting date.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Assets and liabilities recorded at fair value in the unaudited condensed consolidated financial statements are categorized based upon the level of judgment associated with the inputs used to measure their fair value. The fair value of the Company’s financial assets and liabilities reflects management’s estimate of amounts that the Company would have received in connection with the sale of the assets or paid in connection with the transfer of the liabilities in an orderly transaction between market participants at the measurement date. In connection with measuring the fair value of its assets and liabilities, the Company seeks to maximize the use of observable inputs (market data obtained from independent sources) and to minimize the use of unobservable inputs (internal assumptions about how market participants would price assets and liabilities). Hierarchical levels which are directly related to the amount of subjectivity associated with the inputs to the valuation of these assets or liabilities are as follows: Level 1 — Unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access as of the measurement date. Level 2 — Inputs other than quoted prices included within Level 1 that are directly observable for the asset or liability or indirectly observable through corroboration with observable market data. Level 3 — Unobservable inputs for the asset or liability only used when there is little, if any, market activity for the asset or liability at the measurement date. This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to their fair value measurement. The Company’s assessment of the significance of a specific input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. Financial assets and liabilities held by the Company measured at fair value on a recurring basis as of March 31, 2023 and December 31, 2022 include cash and cash equivalents, short-term investments, and convertible notes.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

3 Months Ended

Mar. 31, 2023

The accompanying unaudited condensed consolidated financial statements of the Company have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim reporting and with the instructions to Form 10-Q and Article 10 of Regulation S-X, assuming the Company will continue as a going concern. Accordingly, the condensed consolidated balance sheet at December 31, 2022 has been derived from the audited financial statements at that date, but certain notes or other information that are normally required by GAAP have been omitted if they substantially duplicate the disclosures contained in the Company’s annual audited consolidated financial statements. In the opinion of Stem management, all normal and recurring adjustments considered necessary for a fair statement of the results for the interim period presented have been included in the accompanying unaudited condensed consolidated financial statements. These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2022. Operating results for the three months ended March 31, 2023 are not necessarily indicative of the results that may be expected for the year ending December 31, 2023 or for any other future interim period or year.

Principles of Consolidation

Principles of ConsolidationThe unaudited condensed consolidated financial statements include the accounts of the Company, its wholly-owned subsidiaries, and consolidated variable interest entities (“VIEs”). The Company presents non-controlling interests within the equity section of its condensed consolidated balance sheets, and the amount of consolidated net loss that is attributable to Stem and the non-controlling interest in its condensed consolidated statements of operations. All intercompany balances and transactions have been eliminated in consolidation.

Variable Interest Entities

The Company forms special purpose entities (“SPEs”), some of which are VIEs, with its investors in the ordinary course of business to facilitate the funding and monetization of its energy storage systems. A legal entity is considered a VIE if it has either a total equity investment that is insufficient to finance its operations without additional subordinated financial support or whose equity holders lack the characteristics of a controlling financial interest. The Company’s variable interests arise from contractual, ownership, or other monetary interests in the entity. The typical condition for a controlling financial interest ownership is holding a majority of the voting interests of an entity; however, a controlling financial interest may also exist in entities, such as VIEs, through arrangements that do not involve controlling voting interests.

The Company consolidates a VIE if it is deemed to be the primary beneficiary. The Company determines it is the primary beneficiary if it has the power to direct the activities that most significantly impact the VIEs’ economic performance and has the obligation to absorb losses or has the right to receive benefits of the VIE that could potentially be significant to the VIE. The Company evaluates its relationships with its VIEs on an ongoing basis to determine whether it is the primary beneficiary.

Beginning in January 2022, the Company formed DevCo JVs with the purpose of originating potential battery storage facility projects in the specific locations and conducting early-stage planning and development activities. The Company determined that the DevCo JVs are VIEs as they lack sufficient equity to finance their activities without additional financial support. The Company determined that it has both (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance, and (2) the obligation to absorb losses or receive benefits from the VIE that could potentially be significant. Accordingly, the Company has determined that it is the primary beneficiary of the DevCo JVs, and as a result, the DevCo JVs’ operating results, assets and liabilities are consolidated by the Company, with third party minority owners’ share presented as noncontrolling interest. The Company applied the hypothetical liquidation at book value method in allocating recorded net income (loss) to each owner based on the change in the reporting period, of the amount of net assets of the entity to which each owner would be entitled to under the governing contracts in a liquidation scenario.

Reclassifications

ReclassificationsCertain prior year amounts have been reclassified for consistency with the current year presentation. Such reclassifications have no impact on previously reported net (loss) income, stockholders’ equity, or cash flows.

Use of Estimates

The preparation of unaudited condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the unaudited condensed consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. The Company bases its estimates on historical experience and on various other assumptions believed to be reasonable. Actual results could differ from those estimates and such differences could be material to the financial position and results of operations.

Significant estimates and assumptions reflected in these unaudited condensed consolidated financial statements include, but are not limited to, depreciable life of energy storage systems; the amortization of acquired intangibles; the amortization of financing obligations; deferred commissions and contract fulfillment costs; the valuation of energy storage systems, internally developed software, and asset retirement obligations; and the fair value of equity instruments, equity-based instruments, warrant liabilities, embedded derivatives and net assets acquired in a business combination.

Segment Information

Segment InformationOperating segments are defined as components of an entity for which discrete financial information is available that is regularly reviewed by the Chief Operating Decision Maker (“CODM”) in deciding how to allocate resources to an individual segment and in assessing performance. The Company’s Chief Executive Officer is the CODM. The CODM reviews financial information presented on a consolidated basis for purposes of making operating decisions, allocating resources, and evaluating financial performance. As such, management has determined that the Company operates as one operating segment that is focused exclusively on innovative technology services that transform the way energy is distributed and consumed. The operations acquired as part of the acquisition of AlsoEnergy have been included in the Company’s operating segment.

Concentration of Credit Risk and Other Uncertainties

Financial instruments that potentially subject the Company to concentration of credit risk consist of cash and cash equivalents and accounts receivable. The Company’s cash balances are primarily invested in money market funds or on deposit at high credit quality financial institutions in the U.S. The Company’s cash and cash equivalents are held at financial institutions where account balances may at times exceed federally insured limits. Management believes the Company is not exposed to significant credit risk due to the financial strength of the depository institution in which the cash is held. The Company has no financial instruments with off-balance sheet risk of loss.

At times, the Company may be subject to a concentration of credit risk in relation to certain customers due to the purchase of large energy storage systems made by such customers. The Company routinely assesses the creditworthiness of its customers. The Company has not experienced material losses related to receivables from individual customers, or groups of customers during the three months ended March 31, 2023 and 2022. The Company does not require collateral. Due to these factors, no additional credit risk beyond amounts provided for credit losses is believed by management to be probable in the Company’s accounts receivable.

Significant Customers

Significant CustomersA significant customer represents 10% or more of the Company’s total revenue or accounts receivable, net balance at each reporting date.

Fair Value of Financial Instruments

Assets and liabilities recorded at fair value in the unaudited condensed consolidated financial statements are categorized based upon the level of judgment associated with the inputs used to measure their fair value. The fair value of the Company’s financial assets and liabilities reflects management’s estimate of amounts that the Company would have received in connection with the sale of the assets or paid in connection with the transfer of the liabilities in an orderly transaction between market participants at the measurement date. In connection with measuring the fair value of its assets and liabilities, the Company seeks to maximize the use of observable inputs (market data obtained from independent sources) and to minimize the use of unobservable inputs (internal assumptions about how market participants would price assets and liabilities).

Hierarchical levels which are directly related to the amount of subjectivity associated with the inputs to the valuation of these assets or liabilities are as follows:

Level 1 — Unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access as of the measurement date.

Level 2 — Inputs other than quoted prices included within Level 1 that are directly observable for the asset or liability or indirectly observable through corroboration with observable market data.

Level 3 — Unobservable inputs for the asset or liability only used when there is little, if any, market activity for the asset or liability at the measurement date.

This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to their fair value measurement. The Company’s assessment of the significance of a specific input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability.

Financial assets and liabilities held by the Company measured at fair value on a recurring basis as of March 31, 2023 and December 31, 2022 include cash and cash equivalents, short-term investments, and convertible notes.