A homeowner in Teddington told the BBC "he does not know what to believe" after his home's energy performance was incorrectly rated after he spent £60,000 on green upgrades.

Michael De Podesta, who owns a 1920s semi-detached house in Teddington, told BBC Radio 4's You and Yours about work done to his home such as solar panels and triple glazing to make it more energy efficient.

According to the BBC, "Afterwards, the home was given an EPC (Energy Performance Certificate) rating of B however after having more work carried out it incorrectly went down to a C.

"The company which carried out the last assessment, Compass Property Projects, said it made a mistake however there are calls for the government to overhaul the system."

EPCs, which were introduced in 2007, rate properties by energy efficiency, with the most efficient properties rated A and the least efficient G.

They are important because an EPC is needed to sell or rent out a home. There are plans to force landlords to get all their properties up to a C rating or better by 2030.

"Mr De Podesta, a chartered physicist, started by installing triple glazing, external insulation and solar panels which gave his old house a B rating," the BBC writes.

It added: "Pleased with that, he then completed the final phase of the project which involved getting a heat pump and more solar panels."

The Teddington man told the BBC: "I had this EPC B and thought this house is extraordinarily efficient to run. All the bills for heating last year came to £160 - it's crazily efficient. Surely it should have an A rating?"

Once all the work was finished, he had another EPC assessment and said he was astonished to find that his rating had dropped to a C.

"I just don't know what to trust. I don't think it reliably reflects the state of the property," Mr De Podesta told the BBC.

Compass Property Projects has apologised to Mr De Podesta, refunded him and restored his home's B rating.

It also said an energy performance rating was not a full structural survey.

He has since had another survey, which recorded an A EPC rating.

All EPCs and the people who carry out the assessments must be accredited.

Elmhurst Energy runs software assessors used to collect information, calculate a rating and produce the certificate.

Its CEO, Stuart Fairlie, told the BBC incorrect ratings were a common problem and he has had hundreds of complaints.

"Unfortunately, the methodology which the energy assessors uses is based on price and electricity is more expensive than gas," he said.

According to the BBC, "Mr Fairlie said the process was "out of date" but there was not a lot which could be done unless the government changed the methodology.

"He said he hoped it would happen next year."

Last year, a Which? investigation, external found eight out of 11 homeowners it spoke to found basic errors in the information recorded on their EPCs.

Mr Fairlie told the BBC his company was independent of assessors and tries to "arbitrate for the truth".

"Most of these problems were all about education and telling people that actually, yes you have put this particular type of heating in and that's made a difference, but there were one or two that were honest mistakes by energy assessors and [homeowners] ended up with an incorrect certificate," he added.

The Department of Housing, Communities and Local Government finished a consultation on the topic, external in February.

The department also announced that all rented homes would need to have an EPC rating of at least C by 2028 for new tenancies and all tenancies by 2030.

A spokesperson told the BBC that the department was still working through the responses.