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Electric utility segment - Utility Projects (Details) | 1 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Nov. 30, 2019 USD ($) MW | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Jun. 10, 2019 USD ($) | Oct. 31, 2018 USD ($)
Federal |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |
Tax credit deferral period |  | 25 years |  |  |
State |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |
Tax credit deferral period |  | 10 years |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |
Regulatory liabilities |  | $ 29,760,000 | $ 37,301,000 |  |
Hawaiian Electric Company, Inc. and Subsidiaries | ERP/EAM Implementation Project |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |
ERP/EAM project service period (in years) |  | 12 years |  |  |
ERP/EAM required pass-through savings |  |  |  |  | $ 246,000,000
ERP/EAM implementation project, expected future O&M expense reductions |  |  |  | $ 150,000,000 |
ERP/EAM implementation project, future cost avoidance related to capital costs and tax costs |  |  |  | $ 96,000,000 |
ERP/EAM regulatory liability for operation and maintenance expense reductions |  | $ 8,600,000 |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries | West Loch PV Project |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |
Solar project, energy production (in megawatts) | MW | 20 |  |  |  |
Solar project, project cap | $ 67,000,000 |  |  |  |
Solar project, project cap for in-kind work | $ 4,700,000 |  |  |  |
Solar project, cost incurred |  | 58,800,000 |  |  |
Federal nonrefundable tax credits |  | 14,700,000 |  |  |
State nonrefundable tax credits |  | $ 14,000,000 |  |  |
Solar project, maximum energy costs (in dollars per KWH) |  | 9.56 |  |  |
Regulatory liabilities |  | $ 700,000 |  |  |
Hawaiian Electric | ERP/EAM Implementation Project |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |
ERP/EAM regulatory liability for operation and maintenance expense reductions |  | 5,400,000 |  |  |
HELCO | ERP/EAM Implementation Project |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |
ERP/EAM regulatory liability for operation and maintenance expense reductions |  | 1,300,000 |  |  |
Regulatory liability to be flowed through to customers |  |  | 1,600,000 |  |
Maui Electric | ERP/EAM Implementation Project |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |
ERP/EAM regulatory liability for operation and maintenance expense reductions |  | $ 1,900,000 |  |  |
Regulatory liability, amortization period |  | 5 years |  |  |
Regulatory liability to be flowed through to customers |  |  | $ 2,300,000 |  |

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