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Amperecalc

Heating

Heat pump or gas boiler — which costs less?

Whether a heat pump pays off comes down to a single ratio: electricity price divided by seasonal performance factor, against gas price divided by boiler efficiency. Everything else is detail — which this calculator also models.

How we calculate

Calculation model

  1. 01

    Floor area and building standard give the specific space heating demand; hot water is added from the number of occupants.

  2. 02

    Heat pump electricity follows from heat demand divided by the seasonal performance factor, derived from source and flow temperature.

  3. 03

    The comparison case is priced using boiler efficiency, fuel price and the statutory carbon price.

  4. 04

    Investment less subsidy, together with the annual cost difference, gives the payback.

Good to know

  • The German BEG subsidy for a heating replacement is 30 percent base, plus speed and income bonuses up to a maximum of 70 percent, capped at €30,000 of eligible cost.
  • Flow temperature drives the seasonal performance factor: every degree lower is worth roughly 2.5 percent efficiency.
  • The carbon price on fossil fuels keeps rising, shifting the comparison further towards the heat pump each year.

Law & subsidies

What applies in Germany

Regulation determines the limits and tariffs this calculator works with.

Up to 70 percent towards a heating replacement

The BEG subsidy combines a base grant with speed, income and efficiency bonuses, capped at 70 percent and €30,000 of eligible cost.

Base grant
30 %
Speed bonus
20 %
Income bonus
30 %
Efficiency bonus
5 %
Maximum grant
€21,000
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The speed bonus requires replacing an old but still functioning system. The income bonus applies to owner-occupiers below €40,000 of taxable household income. The efficiency bonus covers natural refrigerants or ground source.

The application must be filed before the work is commissioned — strictly, a supply or service contract with a condition precedent is required.

The carbon price on oil and gas keeps rising

Fossil fuels carry a national carbon price that is scheduled to rise and to move into European emissions trading from 2027.

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The price is already inside the fuel price and, in tenancies, is split between landlord and tenant on a sliding scale — the worse the building's efficiency, the larger the landlord's share.

For the economics this means the gas-versus-heat-pump comparison shifts further towards the heat pump every year, even without any rise in the gas price itself.

This compilation is orientation, not legal advice. Rules in this field change several times a year — check the linked primary source before you invest, or ask a certified specialist.
See all regulatory topics

Frequent questions

Answered briefly.

Does a heat pump require underfloor heating?

No. What matters is the required flow temperature, not the type of emitter. Many existing buildings manage 50 to 55 °C after replacing a few radiators — enough for a seasonal performance factor around 3.0 to 3.4.

What is a good seasonal performance factor?

For air-source heat pumps in existing buildings, 3.0 to 3.5 is realistic; in new builds with underfloor heating, 4.0 to 4.5. Ground-source units sit roughly 0.5 to 1.0 higher.

Is combining it with photovoltaics worth it?

Yes, but less than often assumed: heat demand falls in winter, solar yield in summer. A rooftop array typically covers 20 to 30 percent of heat pump electricity — considerably more for summer hot water.

Rooftop PV calculator

Yield, self-sufficiency and return of a rooftop array over 25 years.

Payback calculator

Net present value, internal rate of return and break-even for any energy investment.

Carbon footprint

Electricity, heat, mobility and diet — and what each measure actually achieves.

All results are model calculations based on your inputs and statistical reference data. They do not replace individual professional planning.

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