Millions of households recommended solar upgrades that will take 134 years to pay off

roof with solar panels and two water heating panels just above the triple glazed skylight
Solar water heating systems can cost up to £5,000 to install and on average save just £44 a year - Andrew Crowley

More than two million homeowners have been told to install solar heating systems which take more than 100 years to pay for themselves in energy savings.

Two thirds of Energy Performance Certificate, or “EPC”, assessments – a requirement when selling a home – undertaken in the last four years recommended solar water heating systems, analysis of four million certificates by data science firm Outra found.

Such systems, recommended above heat pumps and other alternatives, cost up to £5,000 to install and save just £44 a year, with the investment not yielding a net saving on energy bills for 144 years on average.

Solar water heating uses energy from the sun to warm a property’s water for storage in a hot water cylinder or thermal store.

However, because solar energy fluctuates throughout the year, it cannot meet all of a home’s energy needs. Households therefore typically also use a conventional boiler or immersion heater to make up the difference.

It comes amid concerns the EPC system drivers “perverse outcomes”. The assessment prioritises lowering a property’s energy bill, rather than its environmental impact.

This has resulted in some homeowners having their EPC ratings downgraded after installing electric-powered heat pumps, despite their stated benefit on the environment.

Solar heating was the third most recommended home improvement, after insulation and solar panels, both of which have much shorter payback windows and lower upfront costs.

Of all the improvements suggested most commonly suggested after an EPC assessment, solar water heating was the second most expensive, after wind turbine installation, and had the longest payback time.

Installing solar water heating adds a mere 1.9 points to a property’s energy rating, compared to 10.2 for solar panels. Solar panels also save homeowners an average of £390 a year, and take 13 years to pay back.

Other improvements such as low-energy lighting, energy controls and draught-proofing are also much lower in cost and offer a bigger return on investment.

Heat pumps do not feature on the list of recommendations at all, despite a Government-led push to install 600,000 of them a year by 2028.

It follows a decision by Rishi Sunak to relax a string of net zero targets, including rules for landlords which would have forced them to have a C-rated EPC by 2025 for new rental properties, and 2028 for all properties.

The original EPC system – which rates the energy efficiency of homes with A being the best and G being the worst – was introduced under Labour by Labour in 2007, in compliance with a European Union directive. Currently, 45pc of properties in England and Wales fall short of a C rating.

But Housing Secretary Michael Gove said the system has “a number of weaknesses which actually drive some perverse outcomes”.

In March Mr Gove said he was “very worried” that the high costs of energy efficiency improvements could drive landlords out of the market, saying there was “a question about whether EPC is the right measure of energy efficiency overall”.

A study by University College London found that properties could be given poor energy efficiency ratings on the basis of flawed modelling.

Houses in the lowest bands G and F were found to use 48pc less energy in the real world than estimated by the modelling used to rate them, according to the study.

Jessica Few, who led the UCL study, said: “We found that homes in EPC bands C-G on average use significantly less energy than modelled by the EPC.”

There are also concerns assessors are not as well trained as Chartered Surveyors, with fears some are resorting to guessing various elements contributing to the EPC rating such as the age of the building and whether walls are insulated.

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