# NAESB REQ.21 Energy Services Provider Interface (ESPI)

**Canonical:** https://apis.io/apis/naesb/naesb-espi-green-button/  
**Provider:** NAESB — https://apis.io/providers/naesb/  
**Documentation:** https://www.naesb.org/ESPI_Standards.asp

NAESB REQ.21 Energy Services Provider Interface (ESPI) is one of 2 APIs that [NAESB](https://apis.io/providers/naesb/) publishes on the [APIs.io](https://apis.io/) network. Tagged areas include Green Button, ESPI, Energy Usage, Smart Metering, and Authentication. The published artifact set on APIs.io includes API documentation and pricing.

The NAESB REQ.21 ESPI Model Business Practices define the data exchange protocol for transferring retail energy usage information from a utility (Data Custodian) to a Third Party with the Retail Customer's authorization. ESPI is the industry-consensus standard that is the basis of every Green Button implementation in North America and is the standard endorsed by the Green Button Alliance. NAESB publishes the standard; it does not operate an ESPI endpoint — each Data Custodian utility hosts its own, so there is no NAESB base URL. The Atom/XML payload schemas (NAESBespiSchema.xsd and retailcustomer.xsd, v3.3 and v4.0) are released under the Apache License 2.0 as a one-time exception to the NAESB Copyright Policy and are harvested here verbatim. The narrative Model Business Practices themselves are copyright-protected and must be purchased or obtained through NAESB membership. The v4.0 schema encodes an OAuth 2.0 authorization model directly — ApplicationInformation carries authorizationServerAuthorizationEndpoint, authorizationServerTokenEndpoint, authorizationServerRegistrationEndpoint, GrantType, TokenEndPointMethod, scope and OAuthError.

## Machine-readable artifacts (9)

- **XMLSchema** — https://raw.githubusercontent.com/api-evangelist/naesb/refs/heads/main/schemas/naesb-espi_v4.xsd
- **XMLSchema** — https://raw.githubusercontent.com/api-evangelist/naesb/refs/heads/main/schemas/naesb-customer_v4.xsd
- **XMLSchema** — https://raw.githubusercontent.com/api-evangelist/naesb/refs/heads/main/schemas/naesb-espi.xsd
- **XMLSchema** — https://raw.githubusercontent.com/api-evangelist/naesb/refs/heads/main/schemas/naesb-customer.xsd
- **Documentation** — https://www.naesb.org/ESPI_Standards.asp
- **Pricing** — https://www.naesb.org//misc/naesb_matl_order_espi_standards.pdf
- **TermsOfService** — https://www.naesb.org/copyright.asp
- **AgentSkill** — https://raw.githubusercontent.com/api-evangelist/naesb/refs/heads/main/skills/naesb-espi-green-button-authorization.md
- **APIsJSON** — https://raw.githubusercontent.com/api-evangelist/naesb/refs/heads/main/apis.yml

## Other NAESB APIs (1)

- [NAESB Electric Industry Registry (EIR) webRegistry Web Services](https://apis.io/apis/naesb/naesb-eir-webregistry/)

## Tags

Green Button, ESPI, Energy Usage, Smart Metering, Authentication, Retail Electric

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/apis/naesb/naesb-espi-green-button/). The API's provider profile, Kin Score and agent-readiness rating are at https://apis.io/providers/naesb/.