# Hydro One

> Hydro One Limited (TSX: H) is Canada's largest electricity transmission and distribution service provider, transmitting and distributing electricity across Ontario. It operates the provincial transmission grid and a rural/regional distribution network serving roughly 1.5 million customers. Its API posture is defined by regulation, not by product: Ontario Regulation 633/21 (Energy Data) compels Ontario electricity and gas distributors to implement Green Button Download My Data (DMD) and Connect My Data (CMD). Hydro One runs a live Green Button CMD OAuth 2.0 authorization surface and a published third-party vendor onboarding process — but the CMD resource base URI, client credentials and test accounts are issued privately during onboarding and are published nowhere.

Generated by API Evangelist from the Hydro One APIs.json profile. Method: generated. Date: 2026-07-27.
Hydro One does not publish an llms.txt of its own (https://www.hydroone.com/llms.txt returns HTTP 404).

## What an agent needs to know first

- There is **no OpenAPI, Swagger, GraphQL, AsyncAPI or MCP surface** for Hydro One. `/openapi.json` and `/swagger.json` on www.hydroone.com return HTTP 200 with `text/html` — the SharePoint site catch-all page, not a specification. No developer, api, docs or data subdomain resolves.
- The one real API is **Green Button Connect My Data (CMD)**: a NAESB ESPI OAuth 2.0 integration. It is **not self-serve**. A third party must accept the terms, register on the HONI third-party portal, be issued a Client ID, Client Secret, test accounts and URI(s) privately by a Hydro One account executive, and pass connectivity testing within 90 days.
- **Customers, not vendors, authorize.** A vendor cannot submit an authorization on a customer's behalf; the customer authenticates with Hydro One directly and may revoke at any time.
- Hydro One publishes **no open grid, system, outage or market data API**. Ontario wholesale market and system data belongs to the IESO, a separate organization. The Storm Center outage map is a KUBRA-hosted vendor widget, not a documented Hydro One API.

## APIs

- [Hydro One Green Button Connect My Data (CMD)](https://www.hydroone.com/saving-money-and-energy/green-button/third-party-apps): OAuth 2.0 authorization-code access to an individual customer's electricity usage and billing data as NAESB ESPI XML, after that customer consents. Base URI not published.

## Docs

- [Green Button at Hydro One](https://www.hydroone.com/saving-money-and-energy/green-button): overview of Download My Data and Connect My Data.
- [Green Button third-party onboarding](https://www.hydroone.com/saving-money-and-energy/green-button/third-party-apps): vendor entry point and FAQ.
- [Third-party onboarding application form](https://www.hydroone.com/saving-money-and-energy/green-button/third-party-onboarding-form)
- [Green Button Third-Party Terms and Conditions](https://www.hydroone.com/saving-money-and-energy/green-button/third-party-terms-and-conditions): the authoritative technical document — credential issuance, 90-day connectivity testing, RSA 2048-bit certificate exchange, TLS, data retention and destruction.
- [Green Button Connect My Data authorization surface](https://www.hydroone.com/green-button-cmd-home)
- Operational contact: greenbutton@HydroOne.com

## Standards and regulation

- [O. Reg. 633/21 (Energy Data), Electricity Act, 1998](https://www.ontario.ca/laws/regulation/210633): the mandate.
- [Ontario Energy Board — Green Button](https://www.oeb.ca/consumer-information-and-protection/green-button): the regulator's consumer page.
- [Green Button Alliance](https://www.greenbuttonalliance.org/): the standard body; Ontario certification is tied to NAESB REQ.21 ESPI v3.3.
- [Green Button / OpenESPI developer documentation](https://greenbuttonalliance.github.io/OpenESPI-GreenButton-API-Documentation/): the standard's API documentation, not Hydro One's.

## API Evangelist artifacts

- [APIs.json profile](https://raw.githubusercontent.com/api-evangelist/hydro-one/refs/heads/main/apis.yml)
- [Authentication profile](https://raw.githubusercontent.com/api-evangelist/hydro-one/refs/heads/main/authentication/hydro-one-authentication.yml)
- [OAuth scopes (ESPI function blocks)](https://raw.githubusercontent.com/api-evangelist/hydro-one/refs/heads/main/scopes/hydro-one-scopes.yml)
- [API conventions](https://raw.githubusercontent.com/api-evangelist/hydro-one/refs/heads/main/conventions/hydro-one-conventions.yml)
- [Conformance](https://raw.githubusercontent.com/api-evangelist/hydro-one/refs/heads/main/conformance/hydro-one-conformance.yml)
- [Lifecycle](https://raw.githubusercontent.com/api-evangelist/hydro-one/refs/heads/main/lifecycle/hydro-one-lifecycle.yml)
- [Sandbox / connectivity testing](https://raw.githubusercontent.com/api-evangelist/hydro-one/refs/heads/main/sandbox/hydro-one-sandbox.yml)
- [Domain security probe](https://raw.githubusercontent.com/api-evangelist/hydro-one/refs/heads/main/security/hydro-one-domain-security.yml)
- [Well-known probe index](https://raw.githubusercontent.com/api-evangelist/hydro-one/refs/heads/main/well-known/hydro-one-well-known.yml)
- [Packages search](https://raw.githubusercontent.com/api-evangelist/hydro-one/refs/heads/main/packages/hydro-one-packages.yml)
- [Review](https://raw.githubusercontent.com/api-evangelist/hydro-one/refs/heads/main/review.yml)

## Not available

- OpenAPI / Swagger / GraphQL / AsyncAPI / gRPC definitions — none exist.
- SDKs, CLI, Postman collection, embedded components — none published.
- Public MCP server or agent skills — none; there is no specification to ground them in.
- Status page, SLA, changelog, deprecation policy, roadmap — none published.
- security.txt, trust centre, vulnerability disclosure programme — none found.