SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
Jun. 30, 2026
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited interim condensed consolidated financial statements have been prepared on an accrual basis of accounting in accordance with United States Generally Accepted Accounting Principles (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and disclosures normally included in consolidated financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Accordingly, these unaudited interim condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and accompanying notes for the year ended December 31, 2025. The condensed consolidated balance sheet as of December 31, 2025, included herein, was derived from the consolidated financial statements of the Company as of that date. These unaudited interim condensed consolidated financial statements, in the opinion of management, reflect all adjustments, consisting of normal recurring adjustments, necessary to present fairly the Company’s financial position as of June 30, 2026, results of operations and comprehensive loss and stockholders’ equity activities for the three and six months ended June 30, 2026, and cash flows for the six months ended June 30, 2026. The results for the three and six months ended June 30, 2026 are not necessarily indicative of the results to be expected for the year ending December 31, 2026 or for any interim period or for any other future year.
Principles of Consolidation	Principles of Consolidation These unaudited interim condensed consolidated financial statements include Energy Vault Holdings, Inc., its wholly owned subsidiaries, and majority owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements, in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the unaudited interim condensed consolidated financial statements and accompanying notes. The Company evaluates its assumptions on an ongoing basis. The Company’s management believes that the estimates, judgment, and assumptions used are reasonable based upon information available at the time they are made. Estimates made by management include, among others, revenue recognition, debt measured at fair value, provision for credit losses, warranty accruals, warrant liabilities, and stock-based compensation. Due to the inherent uncertainty involved in making assumptions and estimates, changes in circumstances could result in actual results differing from those estimates, and such differences could be material to the Company’s consolidated financial condition and results of operations.
Restricted Cash	Restricted Cash Restricted cash primarily consists of cash deposits held in segregated accounts as collateral for certain debt financing requirements and for guarantees and bonds issued in connection with our customer projects. Under the terms of our senior notes, cash proceeds are restricted until pre-agreed milestones are achieved. Additionally, our contractual arrangements with customers often require us to issue letters of credit, bank guarantees, and performance and payment bonds to secure our performance under those contracts. To collateralize these instruments, we deposit cash in restricted accounts that cannot be used for general corporate purposes until the underlying obligations are settled or the guarantees expire.
Concentration of Credit and Other Risks	Concentration of Credit and Other Risks Financial instruments that subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents, restricted cash, accounts receivable, and customer financings receivable. Risks associated with cash and cash equivalents and restricted cash are mitigated by banking with creditworthy institutions. Such balances with any one institution may, at times, be in excess of federally insured amounts.
Capitalized Software Development Costs	Capitalized Software Development Costs Effective January 1, 2026, due to a change in facts and circumstances, the Company began accounting for its capitalized software development costs using Accounting Standards Codification (“ASC”) ASC 350-40, Internal-Use Software (“ASC 350-40”), rather than ASC 985-20, Costs of Software to Be Sold, Leased, or Marketed (“ASC 985-20”). The Company originally applied ASC 985-20 because it initially intended to allow customers to take possession of the software. The Company no longer offers the software in a manner that permits customers to take possession and instead uses the software solely in hosted software-as-a-service arrangements and in its own operations, including Company-owned energy storage systems. As a result, the Company concluded that ASC 350-40 is the appropriate accounting model beginning January 1, 2026 and applied the change prospectively. Immediately prior to the change, the Company performed an impairment assessment of its capitalized software costs as of December 31, 2025 under ASC 985-20 and determined that no impairment was required. The remaining carrying value was reclassified to internal-use software on January 1, 2026. The change in applicable accounting model had no impact on the Company’s condensed consolidated financial statements.
Recently Adopted Accounting Standards and Recent Accounting Standards Issued, But Not Yet Adopted	Recently Adopted Accounting Standards In July 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2025-05, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets. This ASU addresses the complexity and cost associated with estimating expected credit losses for current accounts receivable and current contract assets that arise from revenue contracts under ASC 606. The main provision applicable to all entities is a new practical expedient which, if elected, permits an entity to assume that current conditions as of the balance sheet date do not change for the remaining life of the asset when developing reasonable and supportable forecasts. The Company elected the practical expedient on January 1, 2026 and the adoption of this standard did not have a material impact on the Company’s consolidated balance sheets, results of operations and comprehensive loss, or cash flows. Recent Accounting Standards Issued, But Not Yet Adopted In November 2024, the FASB issued ASU 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40)—Disaggregation of Income Statement Expenses. The ASU requires the disclosure of additional information about specific costs and expense categories in the notes to the consolidated financial statements. The standard is effective for annual periods beginning after December 15, 2026, and interim periods beginning after December 15, 2027, with early adoption permitted. The standard should be applied on a prospective basis with the option to apply the standard retrospectively. We are currently evaluating the impact this ASU would have on our consolidated financial statements and related disclosures. In September 2025, the FASB issued ASU 2025-06, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software. ASU 2025-06 updates the accounting for internal use software by removing the existing project stage framework and requiring capitalization of qualifying software costs when management has authorized and committed to funding the software project and it is probable that the project will be completed and the software will be used to perform its intended function. The amendments also apply to website development costs currently accounted for under Subtopic 350-50. The standard is effective for annual reporting periods beginning after December 15, 2027, and interim reporting periods within those annual reporting periods. Early adoption is permitted. The amendments may be adopted on a prospective, modified transition, or retrospective basis. The Company is currently evaluating the effect that adoption of ASU 2025-06 will have on its consolidated financial statements and related disclosures. In December 2025, the FASB issued ASU 2025-11, Interim Reporting (Topic 270): Narrow-Scope Improvements, which is intended to improve navigability of the guidance in Topic 270, Interim Reporting, and clarify when it applies. The ASU also addresses the form and content of such financial statements and interim disclosure requirements, and establishes a principle under which an entity must disclose events since the end of the last annual reporting period that have a material impact on the entity. This ASU is effective for annual reporting periods beginning after December 15, 2027, and interim reporting periods within those annual reporting periods, with early adoption permitted. The Company is currently evaluating the impact that ASU 2025-11 will have on its consolidated financial statements and related disclosures.
Lease Revenue	Lease Revenue The Company has one tolling agreement that is accounted for as a lease under ASC 842, Leases (“ASC 842”). The agreement is accounted for as a lease because the customer (the “lessee”) has the right to obtain substantially all of the economic benefits from the use of the energy storage system and has the right to direct its use throughout the agreement's term. The Company, as lessor, is entitled to receive monthly lease payments based on a contractual floor amount (the “Monthly Floor”), which is subject to reduction each month based on the availability and round-trip efficiency of the energy storage system (the “Effective Monthly Floor”). Lease income is recognized monthly based on a straight-line allocation of the Monthly Floor over the term of the contract, to the extent it represents fixed or in-substance fixed consideration. Any difference between the recognized lease income and the Effective Monthly Floor earned in a given period is recorded as an adjustment to lease income in that period. At the end of each contract year, if cumulative lease payments received during the year are less than the sum of the twelve Effective Monthly Floors, the lessee is required to make a true-up payment for the shortfall. The Company is also entitled to variable lease payments equal to a specified percentage of the net market revenue generated by the lessee that exceeds the cumulative Effective Monthly Floors for that contract year. The lease does not contain an option for the lessee to extend the term or purchase the asset. The agreement may be terminated early by either party under certain conditions, including for prolonged force majeure events, or by the non-defaulting party upon an event of default.
Fair Value Measurements	FAIR VALUE MEASUREMENTS Carrying amounts of certain financial instruments, including cash, cash equivalents, restricted cash, accounts payable, and accrued expenses approximate their fair value due to their relatively short maturities and market interest rates, if applicable. The Company categorizes assets and liabilities recorded or disclosed at fair value on the consolidated balance sheet based upon the level of judgment associated with inputs used to measure their fair value. The categories are as follows: •Level 1—Inputs which included quoted prices in active markets for identical assets and liabilities. •Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. •Level 3—Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

6 Months Ended

Jun. 30, 2026

The accompanying unaudited interim condensed consolidated financial statements have been prepared on an accrual basis of accounting in accordance with United States Generally Accepted Accounting Principles (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and disclosures normally included in consolidated financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Accordingly, these unaudited interim condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and accompanying notes for the year ended December 31, 2025. The condensed consolidated balance sheet as of December 31, 2025, included herein, was derived from the consolidated financial statements of the Company as of that date.

These unaudited interim condensed consolidated financial statements, in the opinion of management, reflect all adjustments, consisting of normal recurring adjustments, necessary to present fairly the Company’s financial position as of June 30, 2026, results of operations and comprehensive loss and stockholders’ equity activities for the three and six months ended June 30, 2026, and cash flows for the six months ended June 30, 2026. The results for the three and six months ended June 30, 2026 are not necessarily indicative of the results to be expected for the year ending December 31, 2026 or for any interim period or for any other future year.

Principles of Consolidation

These unaudited interim condensed consolidated financial statements include Energy Vault Holdings, Inc., its wholly owned subsidiaries, and majority owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of the condensed consolidated financial statements, in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the unaudited interim condensed consolidated financial statements and accompanying notes. The Company evaluates its assumptions on an ongoing basis. The Company’s management believes that the estimates, judgment, and assumptions used are reasonable based upon information available at the time they are made. Estimates made by management include, among others, revenue recognition, debt measured at fair value, provision for credit losses, warranty accruals, warrant liabilities, and stock-based compensation. Due to the inherent uncertainty involved in making assumptions and estimates, changes in circumstances could result in actual results differing from those estimates, and such differences could be material to the Company’s consolidated financial condition and results of operations.

Restricted Cash

Restricted cash primarily consists of cash deposits held in segregated accounts as collateral for certain debt financing requirements and for guarantees and bonds issued in connection with our customer projects. Under the terms of our senior notes, cash proceeds are restricted until pre-agreed milestones are achieved.

Additionally, our contractual arrangements with customers often require us to issue letters of credit, bank guarantees, and performance and payment bonds to secure our performance under those contracts. To collateralize these instruments, we deposit cash in restricted accounts that cannot be used for general corporate purposes until the underlying obligations are settled or the guarantees expire.

Concentration of Credit and Other Risks

Financial instruments that subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents, restricted cash, accounts receivable, and customer financings receivable.

Risks associated with cash and cash equivalents and restricted cash are mitigated by banking with creditworthy institutions. Such balances with any one institution may, at times, be in excess of federally insured amounts.

Capitalized Software Development Costs

Effective January 1, 2026, due to a change in facts and circumstances, the Company began accounting for its capitalized software development costs using Accounting Standards Codification (“ASC”) ASC 350-40, Internal-Use Software (“ASC 350-40”), rather than ASC 985-20, Costs of Software to Be Sold, Leased, or Marketed (“ASC 985-20”). The Company originally applied ASC 985-20 because it initially intended to allow customers to take possession of the software. The Company no longer offers the software in a manner that permits customers to take possession and instead uses the software solely in hosted software-as-a-service arrangements and in its own operations, including Company-owned energy storage systems. As a result, the Company concluded that ASC 350-40 is the appropriate accounting model beginning January 1, 2026 and applied the change prospectively. Immediately prior to the change, the Company performed an impairment assessment of its capitalized software costs as of December 31, 2025 under ASC 985-20 and determined that no impairment was required. The remaining carrying value was reclassified to internal-use software on January 1, 2026. The change in applicable accounting model had no impact on the Company’s condensed consolidated financial statements.

Recently Adopted Accounting Standards and Recent Accounting Standards Issued, But Not Yet Adopted

Recently Adopted Accounting Standards

In July 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2025-05, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets. This ASU addresses the complexity and cost associated with estimating expected credit losses for current accounts receivable and current contract assets that arise from revenue contracts under ASC 606. The main provision applicable to all entities is a new practical expedient which, if elected, permits an entity to assume that current conditions as of the balance sheet date do not change for the remaining life of the asset when developing reasonable and supportable forecasts. The Company elected the practical expedient on January 1, 2026 and the adoption of this standard did not have a material impact on the Company’s consolidated balance sheets, results of operations and comprehensive loss, or cash flows.

Recent Accounting Standards Issued, But Not Yet Adopted

In November 2024, the FASB issued ASU 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40)—Disaggregation of Income Statement Expenses. The ASU requires the disclosure of additional information about specific costs and expense categories in the notes to the consolidated financial statements. The standard is effective for annual periods beginning after December 15, 2026, and interim periods beginning after December 15, 2027, with early adoption permitted. The standard should be applied on a prospective basis with the option to apply the standard retrospectively. We are currently evaluating the impact this ASU would have on our consolidated financial statements and related disclosures.

In September 2025, the FASB issued ASU 2025-06, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software. ASU 2025-06 updates the accounting for internal use software by removing the existing project stage framework and requiring capitalization of qualifying software costs when management has authorized and committed to funding the software project and it is probable that the project will be completed and the software will be used to perform its intended function. The amendments also apply to website development costs currently accounted for under Subtopic 350-50. The standard is effective for annual reporting periods

beginning after December 15, 2027, and interim reporting periods within those annual reporting periods. Early adoption is permitted. The amendments may be adopted on a prospective, modified transition, or retrospective basis. The Company is currently evaluating the effect that adoption of ASU 2025-06 will have on its consolidated financial statements and related disclosures.

In December 2025, the FASB issued ASU 2025-11, Interim Reporting (Topic 270): Narrow-Scope Improvements, which is intended to improve navigability of the guidance in Topic 270, Interim Reporting, and clarify when it applies. The ASU also addresses the form and content of such financial statements and interim disclosure requirements, and establishes a principle under which an entity must disclose events since the end of the last annual reporting period that have a material impact on the entity. This ASU is effective for annual reporting periods beginning after December 15, 2027, and interim reporting periods within those annual reporting periods, with early adoption permitted. The Company is currently evaluating the impact that ASU 2025-11 will have on its consolidated financial statements and related disclosures.

Lease Revenue

The Company has one tolling agreement that is accounted for as a lease under ASC 842, Leases (“ASC 842”). The agreement is accounted for as a lease because the customer (the “lessee”) has the right to obtain substantially all of the economic benefits from the use of the energy storage system and has the right to direct its use throughout the agreement's term. The Company, as lessor, is entitled to receive monthly lease payments based on a contractual floor amount (the “Monthly Floor”), which is subject to reduction each month based on the availability and round-trip efficiency of the energy storage system (the “Effective Monthly Floor”). Lease income is recognized monthly based on a straight-line allocation of the Monthly Floor over the term of the contract, to the extent it represents fixed or in-substance fixed consideration. Any difference between the recognized lease income and the Effective Monthly Floor earned in a given period is recorded as an adjustment to lease income in that period.

At the end of each contract year, if cumulative lease payments received during the year are less than the sum of the twelve Effective Monthly Floors, the lessee is required to make a true-up payment for the shortfall. The Company is also entitled to variable lease payments equal to a specified percentage of the net market revenue generated by the lessee that exceeds the cumulative Effective Monthly Floors for that contract year.

The lease does not contain an option for the lessee to extend the term or purchase the asset. The agreement may be terminated early by either party under certain conditions, including for prolonged force majeure events, or by the non-defaulting party upon an event of default.

Fair Value Measurements

FAIR VALUE MEASUREMENTS

Carrying amounts of certain financial instruments, including cash, cash equivalents, restricted cash, accounts payable, and accrued expenses approximate their fair value due to their relatively short maturities and market interest rates, if applicable.

The Company categorizes assets and liabilities recorded or disclosed at fair value on the consolidated balance sheet based upon the level of judgment associated with inputs used to measure their fair value. The categories are as follows:

•Level 1—Inputs which included quoted prices in active markets for identical assets and liabilities.

•Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

•Level 3—Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions.