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Summary of Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2025
Accounting Policies [Abstract] |
Schedule of Property, Plant and Equipment | The major components of depreciable plant and equipment as of December 31, 2025 and 2024 are as follows:
| 2025 |  | 2024
Source of supply | $ | 243,335 |  |  | 228,621 |
Pumping plant | 331,134 |  |  | 301,280 |
Water treatment plant | 396,061 |  |  | 367,836 |
Transmission and distribution plant | 3,323,482 |  |  | 3,015,978 |
General plant | 394,632 |  |  | 335,599 |
Total depreciable plant and equipment | $ | 4,688,644 |  |  | 4,249,314 |
Depreciation is computed using the straight-line method over the estimated remaining service lives of groups of assets. The estimated service lives of depreciable plant and equipment are as follows:
| Useful Lives
Source of supply | 20 to 100 years
Pumping plant | 5 to 70 years
Water treatment plant | 5 to 62 years
Transmission and distribution plant | 10 to 100 years
General plant | 5 to 68 years
Property, Plant and Equipment | The major components of nonutility properties and real estate investments are as follows as of December 31:
| 2025 |  | 2024
Land | $ | 914 |  |  | 915 |
Wholesale water supply assets | — |  |  | — |
Buildings and improvements | 769 |  |  | 399 |
Subtotal | 1,683 |  |  | 1,314 |
Less: accumulated depreciation and amortization | 103 |  |  | 98 |
Total | $ | 1,580 |  |  | 1,216 |
Schedule of Estimated Refunds of Advances for Construction and Contributions in Aid of Construction | Estimated refunds for the next five years and thereafter are shown below:
| Estimated Refunds
2026 | $ | 2,569 |
2027 | 2,535 |
2028 | 2,615 |
2029 | 2,592 |
2030 | 2,549 |
Thereafter | 45,627 |
Schedule of Asset Retirement Obligations | As of December 31, 2025 and 2024, the asset retirement obligation is as follows:
| 2025 |  | 2024
Estimated future retirement costs | $ | 4,220 |  |  | 4,303 |
Discount rate | 6 | % |  | 6 | %
Retirement obligation, present value | $ | 930 |  |  | 887 |
Schedule of Disaggregation of Revenue | Detail of H2O America’s revenue components are as follows for the years ended December 31:
| 2025 |  | 2024 |  | 2023
Revenue from contracts with customers | $ | 805,594 |  |  | 736,326 |  |  | 678,168 |
Alternative revenue programs, net | 6,672 |  |  | 6,181 |  |  | 3,634 |
Other balancing and memorandum accounts and regulatory mechanisms, net | (11,919) |  |  | (153) |  |  | (17,123) |
Rental income | 243 |  |  | 6,085 |  |  | 5,684 |
| $ | 800,590 |  |  | 748,439 |  |  | 670,363 |
Accounting Standards Update and Change in Accounting Principle |
Standard |  | Description |  | Date of Adoption |  | Application |  | Effect on the Consolidated Financial Statements
ASU 2023-09 “Improvements to Income Tax Disclosures” |  | The ASU amends certain income tax disclosure requirements, including adding requirements to present the reconciliation of income tax expense computed at the statutory rate to actual income tax expense using both percentages and amounts and providing a disaggregation of income taxes paid. Further, certain disclosures are eliminated, including the current requirement to disclose information on changes in unrecognized tax benefits in the next 12 months. |  | The ASU was adopted with the annual financial statements for the year ended December 31, 2025. |  | Prospective, with retrospective application also permitted. |  | The standard only resulted in updates to disclosure and did not have a material impact on the Company’s financial position and results of operations.
Standard |  | Description |  | Date of Adoption |  | Application |  | Effect on the Consolidated Financial Statements
ASU 2024-03 “Disaggregation of Income Statement Expenses” |  | The ASU requires disclosure, in the notes to the financial statements, of specified information about certain costs and expenses. The ASU requires disclosure of purchases of inventory, employee compensation, depreciation, and intangible asset amortization in interim and annual reporting periods. Further, other amounts already required to be disclosed in accordance with current U.S. GAAP would be included in the same disclosure as the other disaggregation requirements. Additionally, the ASU requires qualitative descriptions of amounts remaining in relevant expense captions that are not separately disaggregated quantitatively as well as disclosure of selling expenses in annual periods and an entity’s definition of selling expenses. |  | The ASU is effective for H2O America for its annual financial statements for the year ending December 31, 2027 and for interim reporting periods for the year ending December 31, 2028. Early adoption is permitted. |  | Prospective, with retrospective application also permitted. |  | The standard is expected to only result in updates to disclosure and is not expected to have a material impact on the Company’s financial position and results of operations.
ASU 2025-06 “Intangibles-Goodwill and Other-Internal-Use Software (subtopic 350-40)” |  | The ASU updates the accounting for internal-use software by removing project stage references and introduces a new capitalization threshold based on management authorization and project completion probability. The guidance requires evaluation of significant development uncertainty, including novel functionality and unresolved performance requirements. ASU 2025-06 clarifies that capitalized internal-use software costs are subject to the property, plant and equipment disclosure requirements under ASC 360-10. |  | The ASU is effective for H2O America for its annual financial statements for the year ending December 31, 2028 and for interim reporting periods for the year ending December 31, 2028. |  | Prospective, retrospective or on a modified transition approach with early adoption permitted. |  | H2O America is currently evaluating the impact of ASU 2025-06 on its financial statements and will adopt ASU 2025-06 in fiscal year ended December 31, 2028.
Standard |  | Description |  | Date of Adoption |  | Application |  | Effect on the Consolidated Financial Statements
ASU 2025-10 “Government Grants (Topic 832)” |  | The ASU establishes accounting for government grants received by business entities and includes guidance for (1) a grant related to an asset and (2) a grant related to income. The ASU requires that a government grant should not be recognized until it is probable that a business entity will comply with the conditions attached to the grant and the grant will be received. Additionally, the ASU requires that a grant related to an asset be recognized on the balance sheet as the business entity incurs the related costs for which the grant is intended to compensate either as deferred income or an adjustment to the cost basis of the related asset. A grant related to income or a grant recognized as deferred income should be recognized in earnings on a systematic and rational basis over the periods in which the related costs are incurred that the grant is intended to compensate. |  | The ASU is effective for H2O America for annual reporting periods beginning after December 15, 2028 and interim reporting periods within those annual reporting periods. Early adoption is permitted. |  | Retrospective adoption with modified prospective and modified retrospective application also permitted. |  | H2O America is currently evaluating the impact of ASU 2025-10 on its financial statements and will adopt ASU 2025-10 in fiscal year ended December 31, 2029.
ASU 2025-11 “Interim Reporting (Topic 270)” |  | The ASU provides clarity about the current requirements, rather than evaluate whether to expand or reduce interim disclosure requirements. The ASU includes a disclosure principle that requires entities to disclose events since the end of the last annual reporting period that have a material impact on the entity. The intent of the disclosure principle, which is modeled after a previous SEC disclosure requirement, is to help entities determine whether disclosures not specified in Topic 270 should be provided in interim reporting periods. |  | The ASU is effective for H2O America for interim reporting periods within annual reporting periods beginning after December 15, 2027. Early adoption is permitted. |  | Prospective, with retrospective application also permitted. |  | H2O America is currently evaluating the disclosure impact of ASU 2025-11; however, the standard is not expected to impact the consolidated financial position, results of operations or cash flows.

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