If you’ve started researching a whole-house retrofit, you’ve probably noticed the numbers all over the place - one article says £5,000, another says £70,000. Both can be true. The honest answer is that retrofit cost depends entirely on how far you go, what your property is starting from, and how it’s built - there is no single “average” figure that means much on its own.
What follows is a realistic breakdown of what different levels of retrofit actually cost in the UK right now, and what drives the price up or down for your specific home.
The four rough tiers of retrofit
Most retrofit work falls into one of four broad tiers. These are indicative ranges, not quotes - your own figure depends on your property’s size, construction and current condition.
- Quick wins (roughly £1,000-£2,000): loft top-up insulation, draught-proofing, smart heating controls. Usually a small EPC improvement, but the fastest payback.
- Standard upgrade (roughly £5,000-£10,000): cavity wall insulation where applicable, a more efficient boiler, better controls. This is where most homes see a meaningful jump in comfort and EPC band.
- Deep retrofit (roughly £25,000-£45,000): external or internal wall insulation, a heat pump, solar PV, full ventilation strategy. This is a genuine whole-house project, usually done in stages.
- Passivhaus-standard / EnerPHit (£50,000-£100,000+): airtightness testing, comprehensive fabric upgrades and mechanical ventilation with heat recovery, aiming for the very top of the EPC scale.
Why the “official” £30,000 figure rarely matches reality
You may have seen government-linked figures suggesting a deep retrofit costs around £30,000 per home. In practice, independent research tells a different story. A University of Nottingham study assessing 224 properties for a UK-government-funded decarbonisation project found the real average cost of a deep retrofit came in at roughly £69,000 - more than double the commonly quoted figure - with private properties typically falling between £68,000 and £86,000.
That’s not a reason to be discouraged. It’s a reason to plan around your actual property rather than a generic headline number, and to treat any “typical cost” you read online (including the ranges above) as a starting point for a conversation, not a quote.
What actually moves the price
A handful of factors explain most of the variation between a £5,000 job and a £70,000 one:
- Wall construction. Cavity walls are relatively cheap to insulate. Solid brick or stone walls (common in pre-1930s housing) need external or internal wall insulation, which is one of the biggest single costs in most retrofits.
- Current EPC rating. A property starting from an E or F needs more work to reach a good rating than one already at a D - fairly intuitive, but it has a big effect on scope.
- Property size and layout. Cost is roughly proportional to floor area and external wall area, so an end-of-terrace and a detached house of the same square footage won’t cost the same to treat.
- Heating system. Moving from a gas boiler to a heat pump usually also means upgrading radiators or pipework, which adds to the bill beyond the heat pump unit itself.
- How joined-up the work is. Doing insulation, ventilation and heating as one planned project is usually more cost-effective than tackling them separately over several years, because you’re not paying for scaffolding, access or disruption more than once.
Don’t forget the assessment and coordination costs
Especially for larger projects, there’s a cost most people overlook until they’re already partway in: getting the retrofit properly assessed and coordinated (see our plain-English guide to PAS 2035 for what this process actually involves). A retrofit assessment typically runs £400-£600, and coordination/design services on top of that are commonly £1,500-£3,900 + VAT depending on scope. It feels like an extra expense, but it’s what stops you from, say, insulating a wall and trapping damp behind it - a mistake that costs far more to fix later than the assessment would have cost to prevent.
You don’t have to do it all at once
Very few homeowners fund a deep retrofit in a single go, and you don’t need to. A properly planned retrofit can be phased - insulation and draught-proofing first, heating system next, renewables later - as long as each stage is designed with the whole project in mind from the start. That’s the whole point of getting a proper plan early: it lets you spread the cost over years without accidentally working against yourself (for example, sizing a new heat pump for an uninsulated house, then having to adjust it once the insulation goes in).
Get a number for your actual property
National averages are a useful starting point, but the only figure that matters is the one for your house. Our free checker pulls your property’s official Energy Performance Certificate and shows you exactly how each part of your home - walls, roof, windows, heating - is currently rated, which is the starting point for any accurate quote. From there, we can match you with a vetted local retrofit specialist for a no-obligation, property-specific quote.
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