Working file M3.4
Radiator upsize cost for a heat pump (UK 2026)
Radiator upsize cost for a heat pump: installed cost range with each end sourced, BUS grant treatment, payback shape.
Cost in 2026
Radiator upsize cost for a heat pump (UK 2026). The published installed range in 2026 is £1,800 to £4,500 for a full set of upsized radiators in a 3-bed (MCS and Heat Geek publisher). Both ends of that range are stated rather than collapsed to a midpoint, because the spread reflects real differences in scope, access and grant eligibility rather than installer mark-up.
What drives the spread
- Number of rooms; the kitchen and bathroom often retain existing emitters.
- Pipework upsize from 8mm or 10mm microbore to 15mm or 22mm.
- Hidden access cost in solid-floor properties.
- Underfloor heating retrofit is a different exercise at £80 to £140 per m².
Where it sits in the PAS 2035 sequence
Paired with the ASHP install at design stage, not after.
Surveyed 1 October 2026. Ofgem cap for 1 October to 31 December 2026 applied (gas 7.97p, elec 26.32p, gas standing 29.68p, elec standing 54.83p). Next scheduled review 25 November 2026 (January cap announcement). [ref M3.4]
By Oliver Wakefield-Smith, Founder, Digital Signet. Corrections to oliver at digitalsignet dot com.