Calculate your home energy emissions and compare to the UK average. Discover practical ways to reduce your carbon impact.
Calculate your annual energy carbon footprint
Based on UK average carbon intensity of 215 gCO2/kWh for grid electricity. Green tariffs reduce elec emissions to near-zero.
Home energy emissions come from electricity (grid), natural gas heating, and hot water. The UK average is 2.5 tCO2e per year. We explain where emissions come from and how to reduce them.
Your home's carbon footprint comes from two sources: electricity from the grid and natural gas for heating and hot water. Electricity has a "carbon intensity"—measured in grams of CO2 emitted per kilowatt-hour (gCO2/kWh)—which varies depending on how the electricity is generated. Natural gas has a fixed carbon intensity of about 202 gCO2/kWh because it's always burned the same way. The UK average home uses 2,700 kWh of electricity and 11,500 kWh of gas per year, producing about 2.5 tonnes of CO2 annually.
Why Does Electricity Have Varying Carbon Intensity? The UK electricity grid is powered by a mix of sources: coal (declining), gas (still significant), renewables (wind, solar, hydro), and nuclear (low-carbon). On a windy day, renewables might supply 60% of grid electricity, reducing carbon intensity to 100–150 gCO2/kWh. On a calm, cloudy evening, gas plants might supply 70%, pushing intensity to 300+ gCO2/kWh. The UK average is currently 215 gCO2/kWh (2024), down from 250 in 2020. This has halved since 2012 thanks to wind farms and coal plant closures.
The Carbon Cost of Gas vs. Electricity: Natural gas heating (burning methane in your boiler) is inherently high-carbon because burning fossil fuels directly releases CO2. A gas boiler with an annual gas consumption of 11,500 kWh produces about 2.3 tCO2 per year. An electric boiler or air-source heat pump (ASHP) using the same 11,500 kWh of heating energy but drawing from the grid would produce only 2.5 tCO2 using today's grid intensity. However, an ASHP is 3x more efficient than a gas boiler—it produces 3 kWh of heat from 1 kWh of electricity—so it only needs 3,800 kWh to deliver the same heating, producing 0.8 tCO2 per year. This is why heat pumps save 1.5 tCO2 per year despite using electricity.
Green Tariffs and Renewable Electricity: A green or renewable electricity tariff sources your electricity from renewable sources (wind, solar, hydro) or uses REGO certificates to prove renewable origin. This reduces your electricity emissions to nearly zero (small transmission losses aside). If you switch 2,700 kWh/year from grid to green electricity, you save about 0.58 tCO2 per year at no cost (green tariffs typically cost the same or less than fossil fuel tariffs). Switching to green electricity is the fastest emissions reduction you can make.
Practical Emissions Reduction Strategies: From fastest to most impactful: (1) Switch to green electricity (instant, 0.58 tCO2 saved). (2) Lower your heating thermostat by 1°C (saves 3% of gas use, 0.07 tCO2). (3) Insulate your loft (saves 10% of heating, 0.23 tCO2). (4) Cavity wall insulation (saves 15%, 0.35 tCO2, payback in 5–7 years). (5) Replace gas boiler with heat pump (saves 1.5 tCO2, £10,000 upfront but eligible for Boiler Upgrade Scheme grant of £5,000–7,500). A heat pump installation saves more emissions than solar panels and EV switching combined.
Context: What Does 1 tonne of CO2 Look Like? A typical UK car (48 MPG, driven 7,400 miles/year) emits 2.1 tCO2 per year. A transatlantic flight (2 passengers, return) emits 2 tCO2 per person. A British person's total annual carbon footprint (including all activities) averages 10–12 tCO2. Home energy (2.5 tCO2) accounts for about 20% of this. The UK's net-zero target (by 2050) requires reducing average per-person emissions to 2–3 tCO2 annually.
Electricity Carbon Intensity Definition: Grid carbon intensity is the grams of CO2-equivalent emitted per kWh of electricity supplied to the grid (lifecycle perspective). It includes: combustion emissions (gCO2e for burning coal/gas), upstream emissions (mining, transport, refining), and transmission losses (3–4% average in UK). Current UK grid intensity is ~215 gCO2e/kWh (2024 average, down from 250 in 2020). Hourly variation ranges 100–400 gCO2e/kWh depending on wind generation and grid carbon balancing. Renewable sources (wind, solar, hydro) have lifecycle intensities of 10–50 gCO2e/kWh (including manufacturing). Nuclear is ~12 gCO2e/kWh.
BEIS Conversion Factors (2024): UK Department for Energy Security & Net Zero publishes annual conversion factors for GHG reporting. Electricity market-based (supplier mix average): 192–215 gCO2e/kWh depending on supplier. Location-based (UK grid average): 193 gCO2e/kWh. Natural gas: 202 gCO2e/kWh (including methane WTT). Biogenic carbon (from biomass) is excluded. REGO certificates reduce reported scope 2 emissions to ~0 for renewables-backed tariffs (though REGO is a subject of debate regarding additionality).
Scope 1, 2, and 3 Emissions Distinction: Scope 1 = direct emissions (burning gas in home boiler). Scope 2 = indirect emissions from purchased electricity (market-based or location-based). Scope 3 = supply chain and other embodied emissions (manufacturing, transport). For residential carbon footprinting, typically Scope 1 + Scope 2 (market-based) are reported. Green tariffs reduce Scope 2 to ~0 using REGO certificates. Lifecycle emissions (embodied carbon in building fabric, insulation, heating equipment) are not included in operational carbon footprinting but represent 5–10% of 30-year building carbon.
Heat Pump Efficiency and Carbon Advantage: Air-source heat pumps (ASHP) achieve Coefficient of Performance (COP) of 2.8–4.0 in UK conditions (heating output / electricity input). A home needing 11,500 kWh/year of heating (equivalent to burning 11,500 kWh of gas) requires only 3,800–4,100 kWh of electricity with a COP-3 ASHP. At 215 gCO2e/kWh grid intensity, this produces 0.82–0.88 tCO2e/year, versus 2.3 tCO2e from gas boiler (11,500 × 202/1000). Carbon saving: 1.42–1.48 tCO2e/year. With decarbonized grid (sub-100 gCO2e/kWh), carbon saving exceeds 2 tCO2e/year. Heat pump payback is typically 10–15 years (with capital cost) but can be 5–7 years with Boiler Upgrade Scheme £5–7k grant.
Green Tariff Carbon Accounting: Green/renewable tariffs supply electricity from renewables or purchase equivalent REGO certificates (1 REGO = proof of 1 MWh renewable generation somewhere in Europe). Under BEIS guidelines, green-tariff electricity is reported at ~0 gCO2e/kWh (though 3–4% transmission losses and 3–5 gCO2e for REGO certification are sometimes included). Typical premium: £0–50/year (often cheaper than fossil tariffs due to supplier competition). Environmental impact: REGO purchase directly funds renewable deployment projects. Additionality is debated (REGOs do not guarantee new renewable build) but are the standard mechanism for GHG compliance reporting.
Sectoral Carbon Budgets and UK Targets: UK's 6th Carbon Budget (CCC, 2021) requires 78% emissions reduction by 2035 vs. 1990 baseline. Residential sector must reduce emissions 50–70% by 2035 (from 2020 baseline). Decarbonization pathways: (1) Grid decarbonization to ~50 gCO2e/kWh by 2035 (via renewables/nuclear expansion). (2) Heat pump rollout (replacing 2m+ gas boilers by 2035). (3) Fabric efficiency improvements (loft/cavity insulation for 4–5m homes). EPC (Energy Performance Certificate) ratings use SAP (Standard Assessment Procedure) which models operational emissions and provides kWh/m²/year baselines. Net-zero home standards (e.g., Passivhaus, net-zero ready) typically target <50 kWh/m²/year primary energy use.