Grant calculator: net cost in four steps

United Kingdom: a flat £7,500 grant. Germany: 30% to a maximum of 70% of at most €30,000 in eligible costs. Every answer updates the panel at once. Checked on 26 October 2026.

Country Home type

Detached houseSemi-detachedTerracedFlat

Floor area

30 m²500 m²

Please enter 30 to 500 m².

Take the floor area from your EPC or purchase documents. Guessing it skews the result more than any grant rate.

Current heating

Gas boilerOil boilerDirect electricstorage heatersNight storage

Planned installation

Taxable household income

The 30% income bonus only applies to owner-occupiers up to €40,000.

The 20% speed bonus is included when a working gas, oil or night-storage system is replaced by the end of 2028. Gas boilers generally need to be at least 20 years old.

New system

Air sourcemost common Ground sourceborehole or loop Water sourcewell required Biomass boilerUK rural only

5% efficiency bonusNatural refrigerant or ground, water or wastewater heat

Germany works in percentages: 30% base plus bonuses, capped at 70% of at most €30,000 in eligible costs (KfW 458).

Your result is in the panel.

Print this page or note the net cost and grant rate before you collect quotes. Three quotes are common; two are enough to check the order of magnitude.

Grant conditions in detail

Everything you entered stays in this browser tab. No account, no upload, no cookie.

Savings over 20 years

How to read the result

Ranges, not point values

Quotes for the same system differ by several thousand in practice. A single figure would fake precision.

Caps are applied

The calculator caps the German rate at 70% and eligible costs at €30,000. An 85% stack from four components is calculated as 70%.

Parameters and sources: GOV.UK Boiler Upgrade Scheme / Ofgem (UK), KfW 458 / BAFA (Germany). German eligible costs capped at €30,000 for the first home, rate capped at 70%. Checked on 26 October 2026.