Definition: A hybrid (or bivalent) heat pump system pairs an air source heat pump with a boiler in the same home. The heat pump covers most of the annual heating; the boiler steps in during the coldest spells or for instant hot water.
The catch: no grant
Hybrid systems are not eligible for the Boiler Upgrade Scheme — the £7,500 grant requires fully replacing the fossil-fuel heating system (GOV.UK, checked July 2026). That changes the arithmetic: a full heat pump installation at £11,014 — our modelled national mid-point (see how we calculate costs) — drops to around £3,514 after the grant, often undercutting a hybrid that gets no support at all.
Most hybrids keep the existing combi for instant hot water, so no cylinder is needed — one reason they appeal in smaller homes. The controls work around a “bivalent point”: an outdoor temperature, often somewhere around 0–5°C, below which the boiler takes over some or all of the load. Ask the installer how that point is chosen and whether it can shift with tariff prices.
When hybrids still make sense
A hybrid can suit homes that are hard to heat with a heat pump alone — poorly insulated properties, undersized radiators, or households keeping a nearly new boiler — while still cutting gas use substantially. Smart controls pick the cheaper heat source hour by hour based on tariffs and outdoor temperature. Read our full guide to hybrid heat pumps and the air source heat pump glossary entry before deciding.
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