Sustainability consultant Martin Evans of Malthouse Consultancy, says EPCs are an “inadequate method” of trying to improve energy efficiency.

“The EPC masquerades as something it clearly can’t deliver. An Energy Performance Certificate sounds grand when actually it is an assessment that takes minutes and tells you the blindingly obvious.

“It should be a useful analysis of a building to see how well it performs now and what its potential is for the future. But it’s hopelessly simplistic.”

Recommendations include basic tips such as switching to energy efficient light bulbs and insulating a water cylinder. However, he adds that advice to install better insulation is useful.

“Anyone who is serious about making meaningful improvements to the efficiency of their homes should have a more thorough assessment carried out,” Evans adds. This could span two to three weeks and cost in the region of £5,000.

Phasing out gas boilers: Green mortgage rewards

Although the government has scrapped its EPC targets for landlords, it is still committed to phasing out gas boilers and has upped the value of the grant available for replacing them.

Meanwhile, ratings are still being used as incentives by banks and building societies. Green mortgages are available that reward homeowners who have the highest ratings by offering borrowers the cheapest mortgage deals.

But, those striving for a higher efficiency rate will find that EPC recommendations are not specific to their property and may not even be applicable.

Assessors explain it isn’t possible to personalise advice because the reports are generated by the software based on a standard set of questions and are meant as guidance only.

Pushing back on criticism that EPC ratings could be skewed by assumptions, Andrew Parkin managing director of Stroma Certification, an accreditation body for energy assessors, says: “They do use assumptions where necessary – usually where something cannot be assessed or seen without being destructive.

“Any assessment process that must reach a conclusion needs to use assumptions. But these are based on established science, though by their nature they are usually averages or broad assumptions.”

As an example, if a homeowner can’t prove they have a certain type of insulation because they haven’t kept the warranty, the software assumes a default level of insulation that was common in properties of that type and age.

Parkin adds: “I do think EPCs are fit for purpose. But they are currently being asked to do all things for all people and they need to be adapted and improved in several ways.

“I feel that the methodologies used for EPCs are good and based upon well understood and continuously improving science. When applied correctly, they give a good degree of accuracy. They are certainly fit for the purpose that they are currently used for and are a great place to start for future policies, understanding how our buildings perform.”

‘EPCs are misunderstood’

An improvement for homeowners, Parkin says, would be to base the rating on cost, carbon emissions and the amount of energy a property uses.

At a cost of around £30 to complete an assessment, a quick turnaround is necessary leaving assessors little time to linger after the checks are done to explain how the ratings and report work.

Domestic energy assessor Faye Handfield thinks EPCs are a valuable tool for homeowners but without being properly explained, the ratings and reports can be misunderstood.

She carries out EPC assessments for landlords who use her letting agency. She charges £75 and sets aside a morning or afternoon for the visit. She says it takes up to 30 minutes to input the data collected at the property onto the EPC platform. She then spends another hour in the tenant’s home to get a complete picture of how they use the property. Afterwards she discusses the outcomes and recommendations with the landlord.

“It’s tough hearing from assessors about how badly they’re paid and how much they’re disrespected for carrying out what I consider to be an essential document for the millions of people who own a house,” Handfield says.

“If they could spend double the time with owners to truly explain the results and what is going on in their homes, that change would improve our energy efficiency, consumption and attitudes by 30 to 40%.”

Handfield wants to see more money invested in the EPC system, education for homeowners from the EPC community, lenders and energy companies and she wants assessors to be paid better so they can spend more time in the property.

EPC changes on the horizon

For most homeowners, the EPC remains the most accessible tool to help them achieve lower energy bills and greener properties. So it will come as a relief that an update to the way your home is scored is due to be released in spring.

It’s expected to improve the accuracy by removing assumptions made on window sizes typical for the age of the property; it will take into account solar technology such as PV diverters that allow you to heat your hot water, and heat pumps will start to appear in the recommendations.

Related: The first story in YourMoney.com’s special EPC series: Landlord despair: ‘I spent £40k making my flat more energy efficient but my EPC was downgraded’