How much does a full house retrofit cost (UK 2026)

A heat-pump-only retrofit costs £8,000 to £14,000 after the £7,500 Boiler Upgrade Scheme grant. A phased deep retrofit across fabric, ventilation, heating, renewables and controls under PAS 2035 costs £35,000 to £70,000 before grants, or £24,000 to £58,000 net of BUS, GBIS and 0% VAT where eligible.

Where does the £69,000 whole-house figure come from?

The £69,000 figure is the upper end of the Passivhaus Trust UK Cost Benchmark v1.3 January 2026 for a phased EnerPHit-grade deep retrofit on a 90 to 100 m² semi-detached property. It is a top-end figure and does not represent the modal case.

What does net after grants look like?

On the 1930s semi modal case: ASHP-only net £3,000 to £10,500 after BUS. Phased deep retrofit net £24,000 to £46,000 after BUS plus GBIS plus 0% VAT, before any ECO4 layer for eligible households.

When is a partial retrofit the right answer?

When fabric is already at or near current Building Regulations standard (post-2000 stock), or when the household has no realistic five-year window for a phased deeper programme. In those cases an ASHP-only route under BUS is defensible.