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Electric utility segment - Regulatory Proceedings (Details) $ in Thousands |  |  | 6 Months Ended | 12 Months Ended |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Dec. 29, 2023 USD ($) | Dec. 23, 2020 USD ($) | Jun. 30, 2024 USD ($) MWh project | Dec. 31, 2023 USD ($) | Dec. 31, 2019 USD ($) agreement | Mar. 31, 2024 USD ($) agreement | Mar. 11, 2024 USD ($) | Jun. 30, 2023 USD ($) | Jun. 17, 2022 mechanism | Jun. 10, 2019 USD ($) | Oct. 31, 2018 USD ($)
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
PUC proposal period (in days) |  | 45 days |  |  |  |  |  |  |  |  |
Public utilities, modified pilot process proposal period (in days) |  |  | 15 days |  |  |  |  |  |  |  |
Propose pilots annual cap |  |  | $ 10,000 |  |  |  |  |  |  |  |
Performance incentive mechanism, accrued award |  |  |  |  |  |  |  | $ 10 |  |  |
Potential total annual maximum reward |  |  | $ 2,000 |  |  |  |  |  |  |  |
Advanced metering infrastructure term (in years) |  |  | 3 years |  |  |  |  |  |  |  |
Regulatory assets |  |  | $ 322,409 | $ 294,804 |  |  |  |  |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of performance incentive mechanisms | mechanism |  |  |  |  |  |  |  |  | 2 |  |
Multi-year rate period (in years) |  | 5 years |  |  |  |  |  |  |  |  |
Customer dividend, negative adjustment percentage |  | 0.22% |  |  |  |  |  |  |  |  |
Savings commitment liability, annual rate |  | $ 6,600 |  |  |  |  |  |  |  |  |
Earnings sharing mechanism, actual return on equity, dead band percentage above or below target |  |  | 3.00% |  |  |  |  |  |  |  |
Approved return on equity, percentage |  |  | 9.50% |  |  |  |  |  |  |  |
Percentage sharing between customers and utilities |  |  | 0.50 |  |  |  |  |  |  |  |
Earnings sharing mechanism, actual earning, above or below dead band |  |  | 1.50% |  |  |  |  |  |  |  |
Percentage sharing for any further difference |  |  | 0.90 |  |  |  |  |  |  |  |
MPIR and EPRM requested amount |  |  | $ 33,100 |  |  |  |  |  |  |  |
EPRM approved projects | project |  |  | 4 |  |  |  |  |  |  |  |
EPRM approved projects, capital costs |  |  | $ 218,500 |  |  |  |  |  |  |  |
Number of projects | project |  |  | 4 |  |  |  |  |  |  |  |
Estimated capital costs |  |  | $ 712,900 |  |  |  |  |  |  |  |
Prior year deferred cost recovery approved |  |  |  |  |  |  | $ 3,000 |  |  |  |
Decoupling order, service reliability performance, historical measurement period (in years) |  |  | 10 years |  |  |  |  |  |  |  |
Maximum penalty, percent of ROE |  |  | 0.20% |  |  |  |  |  |  |  |
Service reliability, pending adjusted maximum penalty amount |  |  | $ 6,400 |  |  |  |  |  |  |  |
Service reliability, estimated penalties |  |  |  | 3,700 |  |  |  |  |  |  |
Dead band percentage above or below the target |  |  | 3.00% |  |  |  |  |  |  |  |
Call center performance, maximum penalty percentage |  |  | 0.08% |  |  |  |  |  |  |  |
Call center performance, pending adjusted maximum penalty |  |  | $ 1,400 |  |  |  |  |  |  |  |
Number of power purchase agreements (PPAs) (in agreements) | agreement |  |  |  |  | 7 |  |  |  |  |  |
Number of incentive earned power purchase agreements | agreement |  |  |  |  |  | 2 |  |  |  |  |
Incentives accrued |  |  |  | 100 | $ 1,700 | $ 100 |  |  |  |  |
Interpolated RPS rate goal, year one and two (in dollars per MWh) | MWh |  |  | 20 |  |  |  |  |  |  |  |
Interpolated RPS rate goal, year three (in dollars per MWh) | MWh |  |  | 15 |  |  |  |  |  |  |  |
Interpolated RPS rate goal, after year three (in dollars per MWh) | MWh |  |  | 10 |  |  |  |  |  |  |  |
Failure to meet RPS targets, penalty rate (in dollars per MWh) | MWh |  |  | 20 |  |  |  |  |  |  |  |
Accrued estimated rewards |  |  |  | 400 |  |  |  |  |  |  |
Potential total annual maximum reward |  |  | $ 1,500 |  |  |  |  |  |  |  |
Public utilities, grid services procurement performance incentive mechanism, accrued estimated rewards |  |  |  | 1,100 |  |  |  |  |  |  |
Potential total annual maximum reward |  |  | 3,000 |  |  |  |  |  |  |  |
Total annual maximum penalty |  |  | 900 |  |  |  |  |  |  |  |
Interconnection approval PIM, accrued estimated rewards |  |  |  | 3,000 |  |  |  |  |  |  |
Performance incentive mechanism, maximum reward |  |  | $ 2,000 |  |  |  |  |  |  |  |
Performance incentive mechanism, term (in years) |  |  | 3 years |  |  |  |  |  |  |  |
Target performance historical measurement period (in years) |  |  | 10 years |  |  |  |  |  |  |  |
Percent of return on equity |  |  | 0.03% |  |  |  |  |  |  |  |
Pending adjusted amount |  |  | $ 1,000 |  |  |  |  |  |  |  |
Target performance period (in months) |  |  | 10 months |  |  |  |  |  |  |  |
Target deadband period (in months) |  |  | 2 months |  |  |  |  |  |  |  |
Accrued earned rewards, net of penalties |  |  |  | 900 |  |  |  |  |  |  |
Recovery of deferral costs period (in years) | 3 years |  |  |  |  |  |  |  |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries | Honolulu Generating Units 8 and 9 |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
Regulatory asset amortization period |  |  | 9 years |  |  |  |  |  |  |  |
Regulatory assets |  |  | $ 28,300 |  |  |  |  |  |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries | Suspension Of Disconnections |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
Regulatory assets |  |  | 1,700 |  |  |  |  |  |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries | Natural Disasters and Other Casualty Events |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
Regulatory assets |  |  | 30,200 |  |  |  |  |  |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries | COVID-19 |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
Public utilities in regulatory assets | $ 8,800 |  |  |  |  |  |  |  |  |  |
Regulatory assets |  |  | $ 8,300 |  |  |  |  |  |  |  |
Hawaiian Electric, Parent |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
Public utilities retained percentage |  |  | 20.00% |  |  |  |  |  |  |  |
Accrued earned rewards, net of penalties |  |  |  | 1,200 |  |  |  |  |  |  |
Hawaii Electric Light Company, Inc |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
Incentives accrued |  |  | $ 100 |  |  |  |  |  |  |  |
Accrued earned rewards, net of penalties |  |  |  | (600) |  |  |  |  |  |  |
Maui Electric |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
Accrued earned rewards, net of penalties |  |  |  | $ 300 |  |  |  |  |  |  |
Schofield Generation Station | Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
MPIR requested amount |  |  | 16,500 |  |  |  |  |  |  |  |
West Loch PV Project | Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
MPIR requested amount |  |  | 3,300 |  |  |  |  |  |  |  |
Grid Modernization Strategy Phase 1 Project | Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
MPIR requested amount |  |  | 11,200 |  |  |  |  |  |  |  |
Waiawa UFLS Project | Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
EPRM requested amount |  |  | $ 100 |  |  |  |  |  |  |  |
ERP/EAM Implementation Project | Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
ERP/EAM project service period (in years) |  |  | 12 years |  |  |  |  |  |  |  |
ERP/EAM project service, savings over 12 years |  |  |  |  |  |  |  |  |  |  | $ 246,000
Future O&M expense reductions |  |  |  |  |  |  |  |  |  | $ 150,000 |
Future cost avoidance related to capital cost and tax costs |  |  |  |  |  |  |  |  |  | $ 96,000 |
Regulatory liability, amortization period (in years) |  |  | 5 years |  |  |  |  |  |  |  |
Regulatory liability for O&M expense reductions |  |  | $ 13,100 |  |  |  |  |  |  |  |
ERP/EAM Implementation Project | Hawaiian Electric, Parent |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
Regulatory liability for O&M expense reductions |  |  | 1,900 |  |  |  |  |  |  |  |
ERP/EAM Implementation Project | Hawaii Electric Light Company, Inc |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
Regulatory liability for O&M expense reductions |  |  | 4,500 |  |  |  |  |  |  |  |
ERP/EAM Implementation Project | Maui Electric |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
Regulatory liability for O&M expense reductions |  |  | 6,700 |  |  |  |  |  |  |  |
Waena Switchyard/Synchronous Project | Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |  |  |  |  |  |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |  |  |  |  |  |  |  |  |
EPRM requested amount |  |  | $ 2,000 |  |  |  |  |  |  |  |

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