| By Popularity
| Alphabetical (What's This?)|
- Hydro One Inc.
Holding company (formed from Ontario Hydro) with subsidiaries in electricity transmission and distribution, telecom, and energy services businesses.
- Hydro One Networks Inc.
Owns and operates the high-voltage electricity transmission system and rural low-voltage distribution system covering Ontario.
Source for residential services from Ontario Hydro Energy including electricity savings, multi-utility billing system, and a network of home service contractors.
- Ontario Hydro Energy Inc. (OHEI)
Offers energy-related expertise to deliver efficiency and productivity improvements to businesses.