Ofgem will discuss its findings in May

Ofgem says the offers are a fair reflection of the wholesale price and the benefits that come from locally sourced energy.

But the regulator estimates that making money back on domestic micro-generation kits could take 20 years.

There are around 100,000 micro-generation units in Britain.

Ofgem report

Ofgem warned 18 months ago that the rules on micro-generation were too complicated and some people were getting nothing when they wanted to sell back to the grid.

Off-the-peg units being sold at DIY stores have proved popular, although there has been some debate over their environmental significance.

They have included turbines, mini-hydro units using flowing water, solar powered hot water systems and combined heat and power units for the home.

Ofgem was asked by the Treasury last year to review the market arrangements for householders wanting to sell energy back to suppliers.

Better efforts

Some 1,500 people are signed up to sell surplus energy back to the energy companies, marking a rapid rise in recent years.

Domestic wind turbines are becoming more popular

"Our research shows that customers are getting a fair deal for selling back power. However they should be aware that it could take a long time for them to recover their investment," said Ofgem chief executive Alistair Buchanan.

He said that clearer information was still needed to help them find the best deal.

The government has pledged to review the financial incentives for householders to make it easier for them to get financial support for micro-generation.

B&Q sells roof-top solar panel kits from around �3,500 and domestic wind turbines from about �1,900.