Heat Pump vs Gas Boiler: The Full 20-Year Cost Comparison
With Germany mandating renewable heating and the UK offering £7,500 grants, millions of homeowners face the biggest heating decision in decades...
Ready to run the numbers?
Why: Germany's Heizungsgesetz and the UK's heat pump push mean millions of homeowners must choose between gas boiler replacement and heat pumps. This calculator helps you compare costs.
How: We use heat demand by insulation, boiler efficiency, fuel prices, COP, and subsidies to compute annual costs, 20-year TCO, payback, and CO₂ savings.
Run the calculator when you are ready.
Enter your property details. Prices auto-adjust by country. For oil/LPG, enter your fuel price in the gas field.
Cumulative cost over 20 years
Annual running costs
CO₂ emissions breakdown (kg/year)
Payback timeline scenarios
For educational and informational purposes only. Verify with a qualified professional.
1. What Is a Heat Pump? (COP Explained)
A heat pump moves heat from outside (air or ground) into your home using electricity. It doesn't create heat—it transfers it. COP (Coefficient of Performance) = heat output ÷ electricity input. A COP of 3.5 means 1 kWh of electricity delivers 3.5 kWh of heat. Gas boilers are typically 90% efficient (0.9 kWh heat per 1 kWh gas).
Higher COP means lower running costs. COP drops in cold weather; ground-source heat pumps maintain higher COP year-round. Modern air-source units achieve COP 3–4 at 7°C outdoor temperature.
2. Germany Heizungsgesetz 2024 Requirements
The GEG (Gebäudeenergiegesetz) mandates that new and replacement heating systems must use at least 65% renewable energy. Heat pumps qualify. Deadlines: municipalities over 100,000 inhabitants by June 2026; smaller by June 2028. WEG (condo associations) get +2 years.
BEG subsidies can cover up to 70% (30% base + 20% speed bonus + 30% income bonus). Apply via BAFA or KfW before starting work. Non-compliance risks fines and affects property value.
3. UK Boiler Upgrade Scheme (BUS)
The BUS offers £7,500 toward air-source or ground-source heat pump installation. Eligibility: you must own your home (or have landlord permission), replace a fossil fuel or electric heating system, and use an MCS-certified installer. The grant is applied at the point of sale—you pay the net amount.
Apply through your installer. They register the project and claim the grant. You need a valid EPC (no outstanding recommendations for cavity wall or loft insulation in most cases). The scheme runs until 2028.
4. Air Source vs Ground Source
Air-source: €/£15,000–25,000, 1–3 day install, COP 3–4. No groundworks. Works well in moderate climates. Ground-source: €/£20,000–35,000, 1–2 weeks, COP 4–5. Requires drilling or trenches. Better in cold climates, quieter, longer lifespan.
Ground-source needs garden space for horizontal loops or boreholes. Air-source needs an outdoor unit (similar to AC). Both can provide heating and cooling. Ground-source has lower running costs but higher upfront.
5. Installation Costs by Country
Germany: Air-source €15,000–30,000; ground-source €20,000–40,000. Prices include unit, installation, and often buffer tank. BEG can cut net cost by 30–70%. UK: Air-source £10,000–18,000 before BUS; ground-source £18,000–35,000. BUS £7,500 reduces net significantly.
Costs vary by property size, existing system, and installer. Get 3+ quotes. Ensure installer is certified (MCS UK, BWP Germany). Include any electrical upgrades (e.g. 3-phase) in your budget.
6. When NOT to Get a Heat Pump
Poor insulation: Heat demand may be too high; running costs can exceed gas. Insulate first. Inadequate electrical supply: Heat pumps need 16–32 A; older homes may need a fuse upgrade or 3-phase. Small flats: Limited outdoor space for the unit; consider shared systems or district heating.
Very high electricity prices with cheap gas: In some regions, the math can favor gas short-term. But gas prices and carbon taxes are rising. If you're selling soon: Payback is 7–12 years; you may not recoup the investment.
7. Hybrid Systems
A hybrid combines a heat pump with a gas boiler. The heat pump covers most of the load; the boiler kicks in during peak cold. Suits poorly insulated homes or those with limited electrical capacity. Reduces gas use by 60–80%.
Cost: €/£12,000–25,000. Can qualify for subsidies. Good stepping stone if full heat pump isn't feasible yet. Future-proofs for eventual boiler replacement with a larger heat pump.
8. Heat Pump Noise Levels
Outdoor units typically produce 40–60 dB at 1 m. UK permitted development often allows installation if noise limits are met. German TA Lärm sets limits (e.g. 50 dB at night). Newer models are quieter (35–45 dB).
Place the unit away from bedroom windows and consider neighbor impact. Acoustic enclosures can reduce noise. Ground-source has no outdoor unit—only indoor noise from the pump.
9. Cold Climate Performance
COP drops at low temperatures. At -10°C, air-source COP may fall to 2–2.5. Ground-source maintains ~3.5–4. Auxiliary electric heating can supplement during extreme cold. In the UK and Germany, cold snaps are rare enough that heat pumps perform well year-round.
Scandinavian experience shows heat pumps work in cold climates. Sizing matters: installers should size for the worst-case design temperature. Oversizing slightly improves cold-weather performance.
10. Future Gas Price Projections
Carbon taxes are rising (UK, EU ETS). Gas supply faces geopolitical and decarbonization pressure. Gas prices are volatile; electricity from renewables is becoming cheaper and more stable. Heat pump running costs are more predictable.
Over 20 years, gas is likely to become relatively more expensive. Heat pumps benefit from grid decarbonization—lower CO₂ emissions per kWh. Locking in a heat pump now hedges against future gas price risk.
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