Green Button is the North American standard for giving an energy customer machine-readable access to their own usage and billing data. The technical specification is NAESB REQ.21, the Energy Services Provider Interface (ESPI), which defines an Atom/XML data model and an OAuth 2.0 authorization flow. It ships in two very different forms — Download My Data, a file the customer exports, and Connect My Data, an actual API a third party can call with the customer’s consent.
Green Button
Green Button began as a White House initiative and became a real standard: NAESB REQ.21, the Energy Services Provider Interface, defining how a utility exposes a customer’s interval usage and billing data as Atom/XML under an OAuth 2.0 authorization flow. The Green Button Alliance runs certification; versions 3.3 and 4.0 are both in the field.
- Two forms, and they are not equivalent - Download My Data produces a file the customer exports by hand. Connect My Data is an authorized API a third party can call. A utility can truthfully claim “Green Button” while offering only the first.
- Consent-mediated by design - the OAuth flow is the point: the customer authorizes a specific third party to receive their data, which is exactly the primitive the agentic turn needs.
- Certified - the Green Button Alliance operates a public certification directory covering DMD, CMD and the ESPI test suite.
- Voluntary in the United States, mandatory in Ontario - the same standard, two regulatory regimes, which makes it one of the few natural experiments available in energy data.
What the evidence shows
The State of US Energy APIs scored sixty organizations in the market that created this standard. Thirteen investor-owned utilities land in the Minimal band with an agent-readiness of 0.0 — Duke Energy at 3.5, Sempra at 3.5 — and the US finishes last of the four energy markets studied. A decade of availability without an obligation produced adoption that is real but shallow: several utilities publish Download My Data only, and the profiles record that distinction rather than crediting the label.
The State of Canadian Energy APIs covers the one jurisdiction that made it compulsory. Ontario’s O. Reg. 633/21 requires licensed distributors to offer Green Button, and three utilities publish the Green Button Alliance’s ESPI specification as a result — genuine evidence that a mandate produces a shared vocabulary. But the bound utilities cluster in Thin and Emerging, two of them claim a compliance that could not be verified from outside, and the top-scoring organization in Canadian energy is a Quebec Crown corporation under no data mandate at all.
The transferable reading: Green Button is a well-designed standard whose outcome is set almost entirely by the regime around it. Compare the Australian Consumer Data Standards, where a statutory data right produced thirteen live consumer APIs and twelve points of measured difference. The specification is not the variable. The obligation, and whether anyone verifies it, is.
For anyone assessing a utility’s Green Button claim, the question to ask is not whether they support it. It is whether they run Connect My Data, at what ESPI version, and whether the endpoint answers.
Referenced in API Evangelist papers
This standard shows up in my published research. These reports read the machine-readable evidence provider by provider — and put this standard in the context of a real sector.
The OpenAPI Standard
A real standard with no mandate behind it; cited as the contrast case for voluntary adoption.
The State of US Energy APIs
A real standard a decade old that no federal rule compels anyone to implement — and the market that invented it finishes last of four, with 13 investor-owned utilities in the Minimal band.
The State of Canadian Energy APIs
Ontario mandated it by regulation (O. Reg. 633/21) and the bound utilities still cluster in Thin and Emerging — while the country's best energy API belongs to a province with no mandate at all.
