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Hybrid heat pump calculator: when keeping the boiler is the right answer

A hybrid runs the heat pump for most of the year and lets the boiler take the coldest days. That covers 80–90 % of your heat with a much smaller, cheaper heat pump and no radiator work — but you keep a gas standing charge and a boiler service.

When a hybrid is genuinely the better answer

• Your radiators cannot hold a low flow temperature and you are not willing to replace them. The boiler covers the coldest 10 % of the year instead of a radiator project.
• Your boiler is new. Scrapping a five-year-old condensing boiler to save gas is rarely the best use of the money.
• You are off gas on oil or LPG but have a large, poorly insulated house where a full system would need 16 kW or more.
• You want to spread the investment: hybrid now, remove the boiler at its next end of life.

What the hybrid costs you

• You keep the gas standing charge — roughly £106 a year at the current cap — and the annual boiler service.
• Two heat sources means two things to control badly. Hybrids underperform most often because the switchover point is set to favour the boiler.
• In the UK the Boiler Upgrade Scheme does not fund hybrids in the same way as a full replacement — check the current rules before assuming a grant.
• You are still burning gas, so the carbon case is partial.