Short answer
Gas demand equals useful heat divided by seasonal efficiency. Add standing charge, maintenance and known investment, using the same heat demand as the heat pump.
Important variables
- Investment after support
- Useful energy, efficiency and degradation
- Energy prices and tariff
- Horizon and discount rate
RATIOXA TOOLRun your own numbersHeat pump or gas? →
Worked example
20,000 kWh useful heat at 90% efficiency needs about 22,222 kWh gas. At €0.11 that is €2,444 before standing charge.
Break-even: What changes the result?
Test the main driver as a cautious, central and optimistic range. Also check whether the ranking reverses at a crossover or remains robust across the range.
Common mistakes
- Treating subsidy or tariff as certain
- Omitting losses and degradation
- Confusing simple payback with return
Terms in this guide
Sources & assumptions
- KfW Bankengruppe — Heizungsförderung ab 21. Juli 2026 (2026-08-17)
- RATIOXA — Methodology and formulas (2026-08-17)
Continue learning
Continue with your numbers
Was this guide helpful?