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OpenAPI Specification

openapi: 3.2.0
info:
  title: emission-factors.com Fuel Emissions 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: Fuel Emissions
paths:
  /api/fuel-emissions:
    get:
      summary: Scope 1 stationary combustion CO₂e for one fuel (GHG Emission Factors Hub 2026…
      operationId: fuelEmissions
      x-unknown-field-hint: The Hub edition parameter is edition (2026 or 2025).
      parameters:
      - name: fuel
        in: query
        schema:
          type: string
        example: natural_gas
      - name: quantity
        in: query
        schema:
          type: number
        example: 1000
      - name: unit
        in: query
        schema:
          type: string
        example: therm
        description: 'Required with fuel: mmBtu, therm, Dth, scf, ccf, mcf, gallon, liter, barrel, short_ton, lb, tonne'
      - name: edition
        in: query
        schema:
          type: string
          enum:
          - '2026'
          - '2025'
          default: '2026'
        description: '2026: Cornerstone Hub (AR6 GWPs); 2025: EPA Hub (AR5)'
      responses:
        '200':
          description: CO2, CH4, N2O and CO2e (GWPs of the chosen edition)
        '400':
          description: Unknown fuel, unit or edition
      tags:
      - Fuel Emissions
    post:
      summary: Scope 1 CO₂e for several fuels with a total
      operationId: fuelEmissionsBatch
      x-unknown-field-hint: The Hub edition parameter is edition (2026 or 2025).
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
              - items
              properties:
                items:
                  type: array
                  maxItems: 50
                  items:
                    type: object
                    required:
                    - fuel
                    - quantity
                    - unit
                    properties:
                      fuel:
                        type: string
                      quantity:
                        type: number
                      unit:
                        type: string
                edition:
                  type: string
                  enum:
                  - '2026'
                  - '2025'
                  default: '2026'
      responses:
        '200':
          description: Per-item results and total_co2e_kg
        '400':
          description: Invalid item
      tags:
      - Fuel Emissions