Emissionary trains your intuition about everyday CO₂ by comparing pairs of activities. Every figure is use-phase only: the energy consumed while using a product multiplied by the emission factor of its energy source. Manufacturing, embodied carbon, and end-of-life are out of scope.

Figures are transparent approximations based on typical products and cited factors — the game teaches orders of magnitude, not lab-grade precision.

Scoring: 100 points within ±10% of the truth; linear decay in log space to 0 points at 10× off in either direction. Guessing 3× too high costs the same as 3× too low.

Emissionary — data sources and methodology

Generated by scripts/generate-sources-md.ts — do not edit by hand.

Scope and boundary

All figures are use-phase (operational) CO₂ only: the energy consumed while using a product, multiplied by the emission factor of the energy carrier. Manufacturing, embodied carbon, and end-of-life are out of scope. The boundary is symmetric: combustion-only factors for fuels (no well-to-tank) and generation-based grid intensity for electricity (no upstream fuel supply). Gaseous fuel factors use the gross calorific value basis, which pairs consistently with US DOE appliance efficiencies (measured on the HHV basis) and with how gas is metered.

Core factors

• Natural gas: 182.59 gCO₂/kWh thermal, gross CV (DESNZ 2025, CO₂-only component)
• LPG: 214.19 gCO₂/kWh thermal, gross CV (DESNZ 2025)
• Petrol: 2.32567 kgCO₂/L (100% mineral, tailpipe, DESNZ 2025)
• Diesel: 2.62818 kgCO₂/L (100% mineral, tailpipe, DESNZ 2025)
• Grid intensity: yearly gCO₂/kWh per country, Ember (latest year per country; see country_factors.json)
• Water heating: 0.093 kWh useful per liter boiled from 20 °C (4.186 kJ/kg·K × 80 K)

Source registry

codata_physics

NIST — NIST Chemistry WebBook — thermophysical properties of water (specific heat 4.186 kJ/kg·K) (2023). License: Public domain (US federal). Retrieved 2026-07-16. https://webbook.nist.gov/chemistry/fluid/

desnz_2025

UK Government (DESNZ) — Greenhouse gas reporting: conversion factors 2025 (flat file, CO₂-only components) (2025). License: Open Government Licence v3.0. Retrieved 2026-07-16. https://www.gov.uk/government/publications/greenhouse-gas-reporting-conversion-factors-2025

doe_energysaver

US DOE — Energy Saver — appliances and home electronics guidance (typical product-class rated powers; used where no certified dataset exists — flagged for EPREL verification in SOURCES.md) (2026). License: Public domain (US federal). Retrieved 2026-07-16. https://www.energy.gov/energysaver/appliances-and-electronics

doe_tsd_cooking

US DOE — Technical Support Document for Residential Cooking Products (docket EERE-2006-STD-0070): cooking efficiency of gas (~40%) and electric coil (~74%) cooktops (2009). License: Public domain (US federal). Retrieved 2026-07-16. https://downloads.regulations.gov/EERE-2006-STD-0070-0053/content.pdf

ember_yearly

Ember — Yearly electricity data — CO₂ intensity of electricity generation (retrieved via Our World in Data grapher mirror) (2026). License: CC BY 4.0. Retrieved 2026-07-16. https://ourworldindata.org/grapher/carbon-intensity-electricity

energystar

US EPA ENERGY STAR — ENERGY STAR certified product datasets (data.energystar.gov); medians computed from full dataset on retrieval date (2026). License: Public domain (US federal). Retrieved 2026-07-16. https://data.energystar.gov

energystar_induction

US EPA ENERGY STAR — 2021–2022 Residential Induction Cooking Tops program page (~84% induction cooking efficiency) (2021). License: Public domain (US federal). Retrieved 2026-07-16. https://www.energystar.gov/partner-resources/products_partner_resources/brand-owner/eta-consumers/res-induction-cooking-tops

epa_fueleconomy

US EPA / DOE — fueleconomy.gov vehicle data — 2024 Tesla Model Y Long Range AWD (vehicle id 47913), EPA combined 28.7 kWh/100 mi wall-to-wheels (2024). License: Public domain (US federal). Retrieved 2026-07-16. https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=47913

epa_trends

US EPA — The 2024 EPA Automotive Trends Report — MY2023 new-vehicle real-world CO₂ (319 g/mi incl. BEV; +38 g/mi excluding BEV/PHEV) (2024). License: Public domain (US federal). Retrieved 2026-07-16. https://www.epa.gov/automotive-trends

ipcc_2006_v2

IPCC — 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Volume 2: Energy (stationary combustion defaults) (2006). License: IPCC publication terms. Retrieved 2026-07-16. https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html

Items

Verification status

31 of 49 item values come from certified datasets, government conversion factors, regulated test data, or first-principles physics. The following 18 use documented product-class conventions and are flagged for verification against EPREL / measured datasets:

• microwave — Typical countertop microwave draws ~1,100 W while heating (product-class rated input, range 900–1,500 W). Pending certified-dataset verification.
• electric_oven — Electric oven at ~200 °C averages ~2.0 kWh per hour of use, element cycling included (product-class convention). Pending certified-dataset verification.
• espresso_machine — One espresso ≈ 0.02 kWh: heating ~40 mL of brew water plus boiler losses (physics estimate; range 0.01–0.05 kWh). Pending measured verification.
• toaster — Typical 2-slice toaster rated ~1,000 W (product-class range 800–1,500 W). Pending certified-dataset verification.
• air_fryer — Typical air fryer rated ~1,500 W, element cycling brings averages slightly lower (product-class range 1,200–1,800 W). Pending verification.
• heat_pump — A heat pump delivering ~2.8 kW of heat at seasonal COP ~3.5 draws ~800 W of electricity — about 0.29 kWh electric per kWh of heat. Pending dataset verification.
• gas_boiler — A home gas boiler actively heating burns ~12 kW of gas (thermal; modulating range 8–24 kW). Country-invariant. Pending dataset verification.
• electric_blanket — Typical double electric blanket rated ~150 W on high (product-class range 60–200 W). Pending verification.
• hairdryer — Typical consumer hairdryer on high: ~1,800 W (product-class range 1,200–2,200 W). Pending certified-dataset verification.
• hair_straightener — Hair straighteners average ~120 W once at temperature (class range 40–300 W). Pending verification.
• iron — Typical steam iron rated ~1,400 W; thermostat cycling lowers averages (class range 1,000–1,800 W). Pending verification.
• vacuum_cleaner — Corded vacuum cleaners draw ~1,200 W (class range 500–1,800 W; EU ecodesign caps at 900 W). Pending verification.
• laptop — Typical laptop in active use draws ~50 W (class range 20–100 W depending on load). Pending verification.
• gaming_pc — A mid-to-high gaming desktop under game load draws ~350 W including monitor excluded (class range 200–600 W). Pending measured verification.
• game_console — Current-generation consoles draw ~160 W while gaming (class range 70–220 W). Pending measured verification.
• wifi_router — Home Wi-Fi routers draw ~8 W continuously (class range 5–20 W). Pending verification.
• smart_speaker — Smart speakers idle/play at ~3 W (class range 1.5–6 W). Pending measured verification.
• e_bike — A ~0.5 kWh e-bike battery delivers ~45 km of assisted riding ≈ 0.011 kWh/km including charging losses. Pending measured verification.