Why cutting energy bills is the greenest policy of all

Ofgem’s price cap will rise by £63 in October, the third increase in 18 months. For the average UK household on a standard variable tariff, that adds up to roughly £1,717 a year on gas and electricity. And every pound wasted through draughty walls, single-glazed windows, or a G-rated boiler is a pound that could have stayed in your pocket, and a tonne of CO₂ that never reached the atmosphere.

That’s the blunt arithmetic behind a new analysis from the University of Reading, which argues that reducing energy bills is a ‘green win’ for both households and the climate. As reported by the University of Reading, the researchers argue that energy efficiency improvements are the most direct route to lower bills and lower emissions, and that government policy should treat them as two sides of the same coin.

Why this matters for your EPC and your wallet

The Energy Performance Certificate rating on your home is a direct measure of how much you’ll spend on heating and power. Homes rated EPC D or below, about 60% of the UK’s housing stock, waste an estimated £1.2 billion a year in avoidable energy costs. The University of Reading’s analysis aligns with what Energy Saving Trust data has shown for years: the cheapest unit of energy is the one you never use.

For a typical 3-bed semi with cavity walls and loft insulation, moving from EPC D to C could cut annual bills by £350–£500. Add a heat pump and solar panels under the ECO4 scheme, and that figure can top £800. The catch is upfront cost. ECO4 grants are means-tested, but the government’s Great British Insulation Scheme offers partial funding for households on lower incomes. For those outside eligibility, the return on investment for cavity wall insulation (£500–£1,000) is typically two to three winters.

Who qualifies, and who doesn’t

ECO4 is the fourth phase of the Energy Company Obligation, requiring large energy suppliers to fund efficiency upgrades in low-income and vulnerable homes. Eligibility is tied to benefits such as Pension Credit, Universal Credit, or Child Tax Credit, and the property must have an EPC rating of D, E, F, or G. The scheme covers loft and cavity wall insulation, solid wall insulation, heat pumps, and solar PV, but not boilers. The government estimates that around 1.5 million households could benefit, but take-up has been slow: a 2023 National Audit Office report found that only 12% of eligible homes had received upgrades under previous phases.

What this misses is the middle ground. Households just above the benefit threshold, earning £35,000 a year, say, are left to fund their own upgrades. For them, the University of Reading’s ‘green win’ argument is real, but the upfront cost barrier is steeper. A heat pump installation runs £7,000–£13,000 after the Boiler Upgrade Scheme grant of £7,500. Without that subsidy, the payback period stretches beyond a decade for many.

What the Budget should do next

The researchers’ call for lower bills through efficiency is not new, but its timing is sharp. With the October Budget looming, the Treasury has a choice: continue subsidising consumption through the price cap and Energy Price Guarantee, or invest in the fabric of homes so that less energy is needed in the first place. The latter is cheaper in the long run. The Climate Change Committee has said that home energy efficiency upgrades could save the UK £7 billion a year in avoided energy costs by 2035, and cut household bills by £300 a year on average.

Yet the government’s own Net Zero Strategy has no binding target for home efficiency. The ECO4 programme runs until March 2026, but there is no confirmed successor. If the Budget does not extend and expand these schemes, the ‘green win’ described by the University of Reading will remain a theoretical prize for the minority who can afford the upfront cost, and a missed opportunity for the millions stuck in cold, expensive homes.

Households on benefits should check their eligibility for ECO4 through their energy supplier or via gov.uk. For everyone else, the most cost-effective first step is a home energy audit, typically £100–£200, followed by loft insulation (average cost £300–£500, payback 2 years). The clock is ticking: the October price rise hits in just six weeks.