v3.25.4
DESCRIPTION OF THE BUSINESS (Details)
$ in Millions
12 Months Ended
Dec. 17, 2024
CAD ($)
Nov. 21, 2024
CAD ($)
May 01, 2023
CAD ($)
Nov. 29, 2022
CAD ($)
Oct. 13, 2016
Dec. 31, 2025
segment
Dec. 31, 2024
Mar. 04, 2025
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Ownership, percentage           100.00% 100.00%  
Number of reportable segments | segment           3    
Hydro One Networks | 2023 Approved Revenue Requirement                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Transmission revenue requirement       $ 1,952        
Distribution revenue requirement       1,727        
Hydro One Networks | 2024 Approved Revenue Requirement                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Transmission revenue requirement       2,073        
Distribution revenue requirement       1,813        
Hydro One Networks | 2025 Approved Revenue Requirement                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Transmission revenue requirement       2,168        
Distribution revenue requirement       1,886        
Hydro One Networks | 2026 Approved Revenue Requirement                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Transmission revenue requirement       2,277        
Distribution revenue requirement       1,985        
Hydro One Networks | 2027 Approved Revenue Requirement                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Transmission revenue requirement       2,362        
Distribution revenue requirement       $ 2,071        
B2M Limited Partnership | 2025 Approved Revenue Requirement                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Transmission revenue requirement   $ 38            
Hydro One Sault Ste. Marie LP                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Deferred rebasing period (in years)         10 years      
Chatham Lakeshore Limited Partnership | 2025 Approved Revenue Requirement                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Transmission revenue requirement $ 17              
Niagara Reinforcement Limited Partnership | 2020 Approved Revenue Requirement                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Transmission revenue requirement   $ 9            
Hydro One Remotes | 2023 Approved Revenue Requirement                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Distribution revenue requirement     $ 128          
Proposed increase to base rate     3.72%          
B2M Limited Partnership                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Ownership interest in related party (as a percent)           66.00%    
Niagara Reinforcement Limited Partnership                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Ownership interest in related party (as a percent)           55.00%    
Chatham x Lakeshore Limited Partnership                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Ownership interest in related party (as a percent)           80.00% 100.00%  
East-West Tie Limited Partnership                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Ownership interest in related party (as a percent)               48.00%
Province                
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]                
Ownership, percentage           47.10% 47.10%