Home Heating: Gas vs Electric vs Heat Pump — Carbon Comparison
Quick answer: Space heating accounts for roughly 40% of home energy use. A gas boiler emits about 21 kg CO2 per 100 kWh of heat delivered, while an air-source heat pump emits just 4.3 kg — nearly 5 times less. On a clean grid, heat pump emissions drop below 1 kg. Switching from gas to a heat pump can cut your heating carbon footprint by 75–90%.
Why Heating Matters for Your Carbon Footprint
Home heating is the single largest energy expense for most households and one of the biggest sources of personal carbon emissions. In the average UK home, heating accounts for about 40% of total energy use and 2.5–3.0 tonnes of CO2 per year. In colder climates like the northern US or Scandinavia, that figure can reach 4–5 tonnes.
The type of heating system you use makes a dramatic difference. Comparing a traditional gas boiler to a modern heat pump is not just about comfort or cost — it is a 5x difference in carbon emissions per unit of heat.
Heating Systems Compared: CO2 per 100 kWh of Heat
The table below shows CO2 emissions for four common heating technologies, measured per 100 kWh of useful heat delivered to your home. Numbers assume a typical US electricity grid mix (about 0.4 kg CO2/kWh).
| Heating System | CO2 per 100 kWh heat | Efficiency / COP | Annual Cost (avg home) | Upfront Cost |
|---|---|---|---|---|
| Natural gas boiler | ~21 kg | 90–95% | $800–1,200 | $3,000–6,000 |
| Electric resistance heating | ~13 kg | 100% | $1,500–2,500 | $1,000–3,000 |
| Air-source heat pump | ~4.3 kg | 250–400% (COP 2.5–4) | $500–900 | $8,000–15,000 |
| Ground-source heat pump | ~3.3 kg | 350–500% (COP 3.5–5) | $400–700 | $15,000–30,000 |
A gas boiler burns 11.2 kg of natural gas to deliver 100 kWh of heat (at 92% efficiency), releasing about 21 kg CO2. An air-source heat pump with a coefficient of performance (COP) of 3.0 uses only 33 kWh of electricity for the same 100 kWh of heat, emitting roughly 4.3 kg CO2 on the average US grid.
How Your Electricity Grid Changes Everything
The carbon advantage of electric heating depends entirely on how your electricity is generated. On a coal-heavy grid, even a heat pump may emit more CO2 than a gas boiler. On a renewable-heavy grid, the difference is dramatic.
| Grid Type | Grid CO2 Intensity | Gas Boiler (100 kWh) | Electric Resistance (100 kWh) | Heat Pump COP 3 (100 kWh) |
|---|---|---|---|---|
| Coal-heavy (e.g. Poland, parts of India) | 0.8–1.0 kg/kWh | 21 kg | 80–100 kg | 27–33 kg |
| Mixed (US average, UK 2024) | 0.3–0.4 kg/kWh | 21 kg | 30–40 kg | 10–13 kg |
| Nuclear-heavy (France, Sweden) | 0.05–0.1 kg/kWh | 21 kg | 5–10 kg | 1.7–3.3 kg |
| Renewable-heavy (Norway, Iceland) | 0.01–0.03 kg/kWh | 21 kg | 1–3 kg | 0.3–1.0 kg |
Key takeaway: on any grid cleaner than about 0.7 kg CO2/kWh, a heat pump beats a gas boiler on carbon. Most developed countries are already well below that threshold, and the gap will widen as grids decarbonize.
15-Year Lifecycle Cost Comparison
Upfront cost is only part of the picture. Heat pumps cost more to install but less to run. Over a 15-year period for an average US home using 15,000 kWh of heat per year:
| Heating System | Upfront Cost | Annual Running Cost | 15-Year Total Cost | 15-Year CO2 Emissions |
|---|---|---|---|---|
| Natural gas boiler | $4,500 | $1,000 | $19,500 | 47 tonnes |
| Electric resistance | $2,000 | $2,000 | $32,000 | 29 tonnes |
| Air-source heat pump | $12,000 | $650 | $21,750 | 9.7 tonnes |
| Ground-source heat pump | $22,000 | $500 | $29,500 | 7.4 tonnes |
An air-source heat pump breaks even with a gas boiler on total cost after about 12 years — and emits 80% less CO2 over its lifetime. With government rebates (such as the US IRA tax credit of up to $2,000 or the UK Boiler Upgrade Scheme of £7,500), the payback period drops to 5–8 years.
Insulation: The Cheapest Decarbonization Strategy
Before upgrading your heating system, reduce demand. Insulation is the most cost-effective way to cut heating emissions, because it reduces the total energy your home needs regardless of the heating technology.
| Insulation Measure | Heat Loss Reduction | Typical Cost | Payback Period |
|---|---|---|---|
| Loft / attic insulation (270 mm) | 25% | $300–800 | 1–3 years |
| Cavity wall insulation | 20–35% | $500–1,500 | 2–5 years |
| Draught-proofing (doors, windows) | 5–10% | $100–300 | Under 1 year |
| Floor insulation | 5–10% | $500–1,500 | 3–7 years |
| Double or triple glazing | 10–20% | $5,000–15,000 | 10–20 years |
A well-insulated home needs 30–50% less energy to stay warm. Combining good insulation with a heat pump can reduce heating CO2 by up to 90% compared to a poorly insulated home with a gas boiler.
Making the Switch: What to Consider
- Check your grid: Look up your region's electricity carbon intensity. If it is below 0.5 kg CO2/kWh, a heat pump is almost certainly lower-carbon than gas.
- Insulate first: Every dollar spent on insulation reduces the size (and cost) of the heating system you need.
- Consider a hybrid system: In very cold climates, a heat pump paired with a gas backup for the coldest days can cut emissions by 60–70% while avoiding oversizing.
- Check incentives: Many countries offer tax credits, rebates, or low-interest loans for heat pump installation. These can cover 30–50% of the upfront cost.
- Think long-term: Grid electricity gets cleaner every year. A heat pump installed today will emit less CO2 in 2030 than it does in 2026, with no changes needed.
Frequently Asked Questions
Do heat pumps work in cold climates?
Yes. Modern cold-climate air-source heat pumps operate efficiently down to -15°C (5°F) and can still extract heat at -25°C, though COP drops to about 1.5–2.0 at those temperatures. Norway, one of the coldest countries in Europe, has one of the highest heat pump adoption rates in the world — over 60% of homes use them.
Is a heat pump cheaper to run than a gas boiler?
In most regions, yes. At a COP of 3.0 and electricity at $0.14/kWh, a heat pump costs about $0.047 per kWh of heat, compared to $0.06–0.08 per kWh for gas (at $1.00/therm). The savings are larger where gas prices are high or electricity is cheap. Over 15 years, an air-source heat pump typically saves $2,000–5,000 compared to replacing a gas boiler with another gas boiler.
Can I keep my existing radiators with a heat pump?
In many cases, yes — but you may need to upgrade some radiators to larger sizes. Heat pumps work best with lower flow temperatures (35–45°C vs 60–70°C for gas boilers), so larger radiators or underfloor heating help distribute the same heat at a lower temperature. A qualified installer will assess your existing system and recommend any changes.
Data sources: IEA Heating Technology Report (2024), EPA Greenhouse Gas Equivalencies Calculator, US Department of Energy — Heat Pump Systems, Carbon Brief — Heat Pump Analysis (2024), Eurostat Energy Statistics.