v3.24.3
Electric utility segment - Regulatory Proceedings (Details)
$ in Thousands
 9 Months Ended 12 Months Ended
Dec. 29, 2023
USD ($)
Dec. 23, 2020
USD ($)
Sep. 30, 2024
USD ($)
MWh
project
Dec. 31, 2023
USD ($)
Dec. 31, 2019
USD ($)
agreement
Jun. 30, 2024
USD ($)
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                  
Regulatory assets     $ 314,247 $ 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     $ 38,000                  
EPRM approved projects | project     4                  
EPRM approved projects, capital costs     $ 218,500                  
Number of projects | project     2                  
Estimated capital costs     $ 294,200                  
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                
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                  
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     $ 27,500                  
Hawaiian Electric Company, Inc. and Subsidiaries | Suspension Of Disconnections                        
Regulatory Projects and Legal Obligations [Line Items]                        
Regulatory assets     2,300                  
Hawaiian Electric Company, Inc. and Subsidiaries | Natural Disasters and Other Casualty Events                        
Regulatory Projects and Legal Obligations [Line Items]                        
Regulatory assets     38,800                  
Hawaiian Electric Company, Inc. and Subsidiaries | COVID-19                        
Regulatory Projects and Legal Obligations [Line Items]                        
Public utilities in regulatory assets $ 8,800                      
Regulatory assets     $ 7,500                  
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     $ 16,100                  
West Loch PV Project | Hawaiian Electric Company, Inc. and Subsidiaries                        
Regulatory Projects and Legal Obligations [Line Items]                        
MPIR requested amount     3,200                  
Grid Modernization Strategy Phase 1 Project | Hawaiian Electric Company, Inc. and Subsidiaries                        
Regulatory Projects and Legal Obligations [Line Items]                        
MPIR requested amount     16,100                  
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     $ 12,800                  
ERP/EAM Implementation Project | Hawaiian Electric, Parent                        
Regulatory Projects and Legal Obligations [Line Items]                        
Regulatory liability for O&M expense reductions     1,500                  
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     6,800                  
Waena Switchyard/Synchronous Project | Hawaiian Electric Company, Inc. and Subsidiaries                        
Regulatory Projects and Legal Obligations [Line Items]                        
EPRM requested amount     $ 2,500