Description of Business and Basis of Presentation	9 Months Ended
Description of Business and Basis of Presentation	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	Description of Business and Basis of Presentation We are a leading residential solar and energy storage service provider, serving more than 72,000 customers in more than 20 United States ("U.S.") states and territories. Sunnova Energy Corporation was incorporated in Delaware on October 22, 2012 and formed Sunnova Energy International Inc. ("SEI") as a Delaware corporation on April 1, 2019. We completed our initial public offering on July 29, 2019 (our "IPO"); and in connection with our IPO all of Sunnova Energy Corporation's ownership interests were contributed to SEI. Unless the context otherwise requires, references in this report to "Sunnova," the "Company," "we," "our," "us," or like terms, refer to SEI and its subsidiaries. Our goal is to be the leading provider of clean, affordable and reliable energy for consumers, and we operate with a simple mission: to power energy independence. We were founded to deliver customers a better energy service at a better price; and through solar and solar plus energy storage service offerings, we are disrupting the traditional energy landscape and the way the 21st century customer generates and consumes electricity. We have a differentiated residential solar dealer model in which we partner with local dealers who originate, design and install our customers’ solar energy and energy storage systems on our behalf. Our focus on our dealer model enables us to leverage our dealers’ specialized knowledge, connections and experience in local markets to drive customer origination while providing our dealers with access to high quality products at competitive prices and technical oversight and expertise. We believe this structure provides operational flexibility and lower fixed costs relative to our peers, furthering our competitive advantage. We provide our services through long-term residential solar service agreements with a diversified pool of high credit quality customers. Our solar service agreements typically are structured as either a legal-form lease (a "lease") of a solar energy system to the customer, the sale of the solar energy system's output to the customer under a power purchase agreement ("PPA") or the purchase of a solar energy system with financing provided by us (a "loan"). The initial term of our solar service agreements is typically 25 years, during which time we provide or arrange for ongoing services to customers, including monitoring, maintenance, and warranty services. Our lease and PPA agreements typically include two five-year automatic extensions. Customer payments and rates can be fixed for the duration of the solar service agreement or escalated at a pre-determined percentage annually. We also receive tax benefits and other incentives from leases and PPAs, a portion of which we finance through tax equity, non-recourse debt structures and hedging arrangements in order to fund our upfront costs, overhead and growth investments. Basis of Presentation The accompanying interim unaudited condensed consolidated financial statements ("interim financial statements") include our consolidated balance sheets, statements of operations, statements of redeemable noncontrolling interests and stockholders' equity and statements of cash flows and have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") from records maintained by us. We have condensed or omitted certain information and note disclosures normally included in the financial statements prepared in accordance with GAAP pursuant to the applicable rules and regulations of the Securities and Exchange Commission ("SEC") regarding interim financial reporting. As such, these interim financial statements should be read in conjunction with our 2018 audited annual consolidated financial statements and accompanying notes included in the prospectus dated July 24, 2019 filed with the SEC pursuant to Rule 424 promulgated under the Securities Act of 1933, as amended. The interim financial statements reflect all normal recurring adjustments necessary, in our opinion, to state fairly our financial position and results of operations for the reported periods. Amounts reported for interim periods may not be indicative of a full year period because of seasonal fluctuations in demand for power, timing of maintenance and other expenditures, changes in interest expense and other factors. Our interim financial statements reflect our accounts and operations and those of our subsidiaries in which we have a controlling financial interest. In accordance with the provisions of the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC") 810, Consolidation, we consolidate any VIE of which we are the primary beneficiary. We form VIEs with our investors in the ordinary course of business to facilitate the funding and monetization of certain attributes associated with our solar energy systems. 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. ASC 810 requires a variable interest holder to consolidate a VIE if that party has (a) the power to direct the activities of the VIE that most significantly impact the VIE's economic performance and (b) the obligation to absorb losses or the right to receive benefits from the VIE that could potentially be significant to the VIE. We do not consolidate a VIE in which we have a majority ownership interest when we are not considered the primary beneficiary. We have considered the provisions within the contractual arrangements that grant us power to manage and make decisions that affect the operation of our VIEs, including determining the solar energy systems contributed to the VIEs, and the installation, operation and maintenance of the solar energy systems. We consider the rights granted to the other investors under the contractual arrangements to be more protective in nature rather than participating rights. As such, we have determined we are the primary beneficiary of our VIEs and evaluate our relationships with our VIEs on an ongoing basis to ensure we continue to be the primary beneficiary. We have eliminated all intercompany accounts and transactions in consolidation. Corporate Reorganization In connection with our IPO we implemented an internal reorganization that resulted in SEI owning all the outstanding capital stock of Sunnova Energy Corporation (the "Reorganization"). In connection with the Reorganization, a direct, wholly-owned subsidiary of SEI merged with and into Sunnova Energy Corporation, with Sunnova Energy Corporation surviving as a direct, wholly owned subsidiary of SEI. Each share of each class of Sunnova Energy Corporation stock issued and outstanding immediately prior to the Reorganization, by virtue of the Reorganization and without any action on the part of the holders thereof, automatically converted into an equivalent corresponding share of stock of SEI, having the same designations, rights, powers and preferences and the qualifications, limitations and restrictions with respect to SEI as each such corresponding share of Sunnova Energy Corporation stock being converted had with respect to Sunnova Energy Corporation. Accordingly, upon consummation of the Reorganization, each of Sunnova Energy Corporation’s stockholders immediately prior to the consummation of the Reorganization became a stockholder of SEI. Reverse Stock Split In connection with our IPO we decreased the total number of outstanding shares with a 1 for 2.333 reverse stock split effective July 29, 2019 (the "Reverse Stock Split"). All current and past period amounts stated herein have given effect to the Reverse Stock Split. Reclassifications Certain prior period amounts have been reclassified to conform to the current period presentation. These reclassifications did not have a significant impact on our interim financial statements.