The 71-year-old, who lives in Trueman Close, impressed onlookers at the Kenilworth Green Fair last week when he exhibited a miniature version of his home-made solar-powered water heating system.

And Mr Gerrard is encouraging others to give it a go for themselves.

He said: "I've built two other solar water panels in two different houses.

"There is some very sophisticated equipment about, but mine is the simplest possible, with no moving parts other than the water.

“Anyone with the skills and the confidence can do it too.

"This technology has been around for about 40 or 50 years - it has just taken a long time for the powers that be to recognise it.

"There must be at least a dozen firms setting up this type of equipment - someone will come round to your house tomorrow if you showed the interest."

Mr Gerrard said the cheapest versions of a ready-made solar-powered water heating system would be around £3,000.

He spent less than £1,000 on materials - and he now saves on heating bills throughout the summer and during parts of the cooler months.

But he said: "I did it more for the principle - to help save energy, and out of a certain amount of frustration at the authorities which are not prepared to make it easier for those to want to make changes."

He added: "It's really just DIY experience - doing jobs around the house myself because I couldn't afford to pay for professionals to do it.

“I'm sure there are others like me who could make their own solar heating system as well."