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OpenAPI Specification

openapi: 3.2.0
info:
  title: emission-factors.com Cleanest Hours API
  version: 2.1.0
  description: 'US electricity and fuel emission data by ZIP code: EPA eGRID Scope 2 factors (location-based) with the Green-e residual mix (market-based), Scope 1 fuel factors, EIA retail rates and hourly grid intensity, EPA CAMD plant emissions and OpenEI utility tariffs. Free, no key. Query parameters and JSON body fields not listed here are rejected with 400.'
  contact:
    url: https://emission-factors.com
  license:
    name: 'Data licenses vary by source: US government works (public domain); eGRID2024, GHG Hub 2026, OpenEI URDB and ZIP-to-utility data, and GeoNames are CC-BY-4.0; the Green-e residual mix is published by the Center for Resource Solutions. See /methodology.'
    url: https://emission-factors.com/methodology
servers:
- url: https://emission-factors.com
  description: Production
tags:
- name: Cleanest Hours
paths:
  /api/cleanest-hours:
    get:
      summary: Cleanest contiguous N-hour window of the day to run a flexible load (EIA-930…
      operationId: cleanestHours
      parameters:
      - name: zip
        in: query
        schema:
          type: string
        example: '94105'
      - name: ba
        in: query
        schema:
          type: string
        description: Balancing authority code instead of zip, e.g. CISO
      - name: duration
        in: query
        schema:
          type: integer
          minimum: 1
          maximum: 12
          default: 4
      - name: between
        in: query
        schema:
          type: string
        example: 20-06
        description: Optional local hours the window must fall in (start-end, wrapping past midnight), e.g. 20-06 for overnight EV charging
      responses:
        '200':
          description: cleanest_window and dirtiest_window (UTC and the ZIP's local time), savings %, hours ranked. For a nearly carbon-free or flat grid both windows are null and no_window_reason says why.
        '400':
          description: Invalid duration or input
        '404':
          description: ZIP not covered by EIA-930 (AK, HI, PR)
        '503':
          description: EIA-930 API temporarily unavailable; retry (Retry-After header)
      tags:
      - Cleanest Hours