Annual house price growth edged up to 1.5% in June, Nationwide reported this week. That is the highest rate since January 2023, and it takes the average UK home to £266,064. For the millions of homeowners sitting on properties built before 1990, roughly two-thirds of the housing stock, the headline figure masks a far more consequential shift: the value of a home is increasingly tied to its Energy Performance Certificate rating.
The Nationwide index, as reported by Nationwide, records a modest uptick. But the data also shows that the market is bifurcating. Buyers are increasingly factoring in energy costs and retrofit requirements. A 3-bed semi in a mid-market suburb with an EPC D or below now sits on the market 18 days longer than an equivalent C-rated property, according to Rightmove data from Q1 2025.
Who qualifies, and who doesn’t
The government’s stated target is for all homes to reach EPC C by 2035. For private landlords, the deadline is tighter: new tenancies must meet EPC C from 2028, existing tenancies from 2030. The penalty for non-compliance is up to £30,000 per property. Owner-occupiers are not yet legally obliged to upgrade, but mortgage lenders are moving faster than the legislation. Barclays and Nationwide Building Society both offer lower rates for homes with EPC A or B. Halifax is piloting a green mortgage product that drops the rate by 0.25% for buyers of C-rated homes.
The catch is that the average UK home sits at EPC D. Of the 29 million homes in England and Wales, only 40% are rated C or above. The remaining 17 million homes require some combination of loft insulation, cavity wall fill, double glazing, or a heat pump to climb the ladder. The Energy Saving Trust estimates the typical cost to move from D to C is between £8,000 and £15,000, depending on the property type and existing fabric.
What it costs a typical 3-bed semi
Take a 1970s semi-detached house in the Midlands, currently rated D. It uses 14,000 kWh of gas and 3,500 kWh of electricity per year. The annual energy bill, under the October 2025 price cap, would be roughly £2,150. Upgrade to C with 270mm loft insulation, cavity wall fill, double glazing, and an A-rated gas boiler, the total cost is around £9,500. The annual bill drops to £1,580. That is a saving of £570 a year, giving a payback period of about 17 years. Add a heat pump under the Boiler Upgrade Scheme, which offers a £7,500 grant, and the payback shrinks to under 10 years.
But the capital gain is the real prize. Research from Nationwide itself shows that homes with an EPC A or B sell for 5% more than equivalent D-rated properties. On a £266,000 average home, that is £13,300. The premium for a C-rated home is smaller but still material: around 2-3%, or £5,300-£8,000. For a seller planning to move within five years, the retrofit pays for itself at the point of sale.
What this misses
The EPC system itself is flawed. It measures fabric efficiency and heating cost, not actual carbon emissions or comfort. A home with a heat pump and poor insulation can score a C, while a well-insulated home with a gas boiler might also score a C. The government’s proposed reforms, including a new metric for smart meter data and in-use performance, have been delayed until at least 2027. Until then, the current EPC remains the only game in town for mortgage offers and rental compliance.
Yet the market is already pricing in the future. Estate agents in areas with older housing stock, such as the North West and South West, report that buyers are asking for EPC certificates before booking viewings. In London, where flats dominate and service charges can include energy costs, a poor EPC can knock £20,000 off the asking price in a competitive market.
Who pays, and when
Landlords face the most urgent timeline. From 2028, a rental property without an EPC C cannot be let to a new tenant. That means any landlord planning to sell in the next five years faces a choice: spend up to £15,000 now or sell at a discount to a buyer who will. The National Residential Landlords Association estimates that 600,000 rental properties currently sit below C, representing a potential £9 billion retrofit bill.
For owner-occupiers, the pressure is less immediate but no less real. Mortgage lenders are likely to introduce EPC-linked loan-to-value caps within the next three years, according to a 2024 report from the UK Finance trade body. A home with an EPC E or F could see its maximum borrowing reduced by 10-15%, effectively pricing it out of the mainstream market. The government has not confirmed any such policy, but the direction of travel is clear.
Households on standard variable tariffs should check their EPC rating on the gov.uk portal this week. If it is D or below, the cheapest first step is loft insulation, typically £500-£700 installed, with a payback of under two years. The Green Homes Grant is no longer running, but the Energy Company Obligation (ECO4) scheme offers free or subsidised insulation for low-income households. Applications are open until March 2026.
Frequently Asked Questions
Not yet, but the market is moving that way. Buyers are increasingly factoring in energy costs and retrofit requirements. Homes with EPC D or below sit on the market longer and sell for less, typically 2-5% below equivalent C-rated properties. Mortgage lenders are also piloting EPC-linked rates, which could make it harder to get a loan for a low-rated home within the next three to five years.
Start with loft insulation (typically £500-£700 installed, payback under two years) and cavity wall insulation (£1,000-£2,000). If your boiler is more than 15 years old, replacing it with an A-rated model can add several points. The Energy Company Obligation (ECO4) scheme provides free or subsidised insulation for eligible low-income households. Check your eligibility on the Ofgem website.
