Retrofit cost calculator
Estimate the cost of insulation, heat pumps, solar and other retrofit measures — with the Boiler Upgrade Scheme grant applied automatically where it fits, and ECO4 / Warm Homes routes flagged where they might cover the work in full.
Tell us about your home
Property type
Wall construction
Current heating
EPC rating
Used to indicate which grant routes you might qualify for.
Measures to estimate
Pick everything you're considering. You can change selections at any time — costs update live.
Insulation
Glazing
Heating
Renewables
Assessment
Estimated cost
Indicative ranges for a typical medium-sized property.
Select one or more measures on the left to see cost estimates.
How this works
The calculator applies published cost ranges per measure, adjusts them by your property type (a small flat costs less to retrofit than a large detached), and shows where the Boiler Upgrade Scheme and other grants might offset the cost.
- Boiler Upgrade Scheme is applied automatically — £7,500 for an air or ground source heat pump, £5,000 for biomass — because the grant amounts are fixed and most homeowners and small landlords in England and Wales are eligible. Read more about BUS.
- ECO4 is flagged but not auto-applied because eligibility depends on your income or benefits status, which the calculator doesn’t ask about. If you qualify, ECO4 typically funds the whole package. Check ECO4 eligibility.
- Warm Homes: Local Grant is flagged where the EPC band suggests it’s likely targeted at your home. It hasn’t opened locally yet. Read more about Warm Homes Plan.
- Smart Export Guarantee applies to solar PV after install. It’s a tariff paid by your electricity supplier for surplus exported electricity, not a grant.
Frequently asked questions
Are these costs accurate for my property?
They are indicative ranges, calibrated for a typical UK property and adjusted by property type, not specific to your home. Real installation costs depend on your property's condition, access, the specification chosen, and the installer. Use the ranges as a sanity check when comparing quotes, not as a substitute for getting them.
Where do the cost ranges come from?
Published ranges from the Energy Saving Trust, the Department for Energy Security and Net Zero, MCS-certified installer data, and the National Energy Foundation, calibrated against 2025–2026 prices. Sources are cited under each measure on the page. Where ranges are wide, the property variability is real — solid wall insulation in particular spans a wide range depending on system choice and specification.
Why does the calculator not apply ECO4 automatically?
ECO4 eligibility depends on income, benefits, and your council's ECO4 Flex criteria — none of which the calculator asks about. The eligibility check is a separate tool. If you do qualify, ECO4 typically funds the work in full as part of a whole-house package, so the cost is effectively £0 to you.
Why does the Boiler Upgrade Scheme deduction look so high?
BUS pays £7,500 towards an air or ground source heat pump (£5,000 for a biomass boiler). It's deducted from your installer's quote at the install stage, so the figure shown after BUS is what you would actually be billed.
Should I install measures in a specific order?
For most properties, insulation comes first. A well-insulated home needs a smaller heat pump (lower upfront cost) and runs it for less of the year (lower running cost). It's also a requirement for the Boiler Upgrade Scheme that loft and cavity wall insulation recommendations on your EPC are addressed (or an exemption applies). See our retrofit guides for more detail by property type.
My property is in a conservation area — does that affect the numbers?
It can. External wall insulation is often restricted on conservation-area frontages, so you may need internal wall insulation only or breathable specifications, which adjusts the cost. Window replacement may require timber or slimline systems rather than standard uPVC. The calculator shows broad ranges that include these variants, but specific quotes will reflect what your property and planning context allow.
Sources
- Energy Saving Trust — measure cost ranges
- gov.uk — Boiler Upgrade Scheme grant amounts
- Ofgem — Energy Company Obligation (ECO4)
- MCS Certified — installer and product data
- National Energy Foundation
See our full data sources page.