Working file V5
Deep retrofit vs heat pump only (UK 2026)
Deep retrofit vs heat pump only (UK 2026): side-by-side decision aid with capex, grant treatment, payback shape and surveyor's note.
| Dimension | HP-only | Phased deep |
|---|---|---|
| Gross capex | £10,500 to £18,000 | £35,000 to £70,000 |
| Grant offset | £7,500 BUS | BUS + ECO4 (if eligible) + GBIS + 0% VAT |
| Net capex | £3,000 to £10,500 | £23,000 to £55,000 |
| Payback at Q3 2026 cap | above 5 to 10 years | above 8 to 18 years |
| Carbon-delta | Largest single step | Reaches EPC A trajectory |
Payback ribbonYears to break even, at Q3 2026 Ofgem cap.
ECO4 cliff
BUS review (~2028)
0 yr5 yr10 yr15 yr20 yr
5 to 18 years to break even at the Q3 2026 Ofgem cap.
Surveyed 22 June 2026. Ofgem Q3 2026 cap applied (gas 7.33p, elec 26.11p, gas standing 29.04p). Next scheduled review 26 September 2026 (Q4 cap publication). [ref V5]
By Oliver Wakefield-Smith, Founder, Digital Signet. Corrections to oliver at digitalsignet dot com.