http://www.guardian.co.uk/money/2010/aug/25/british-gas-solar-panel-installation

More than 12 million homeowners would be in line to save up to £1,000 a year, should they install solar panels, says British Gas.

The utility firm is the latest in a host of companies offering to install electricity-generating systems on homes to take advantage of a government scheme that pays the owners of solar panels for the 'renewable' electricity they generate.
The sudden allure of solar power is less to do with planet-saving and more to do with companies or individuals banking the lucrative feed-in-tariffs (Fits) for every unit of electricity generated – currently 41.3p per KWh, irrespective of whether you consume the power at the time or not.
British Gas says the Fits payments can be worth £1,000 per annum, though with export tariffs (for power not used) added, they can be worth even more. They are guaranteed by the government for 25 years, are payable via the utility company, and will rise in line with inflation.
British Gas has entered the market with the launch of two schemes. If you opt for its "rent-a-roof" scheme, it will install solar panels on your roof for free and you will benefit from the electricity you generate during the day. The installation is free but you will not own the panels and so British Gas will pocket the Fits cash for the length of the scheme – 25 years. The rent-a-roof deal is limited to the first 1,500 British Gas customers who apply.
Alternatively, you can install your own solar panels and British Gas will offer you a two-year interest-free loan, supplied by Hitachi Capital, with which to borrow the upfront costs. You will receive the feed-in-tariffs as well as benefit from the generation of cheaper power. BG says the upfront cost generally ranges from £10,000 to £15,000 depending on the size of the roof.
With the latter deal, consumers should be aware that they will need to ensure they keep up with repayments, which could be as much as £625 per month on a £15,000 across 24 months.
Cathy Debenham, who runs YouGen.co.uk, a website devoted to helping people thinking of installing this, and other similar technology says the rent a roof scheme, "does not sound any different from anyone else's scheme. The savings they make will depend on their electricity usage and their supplier."
In short, different suppliers treat exported energy differently so some customers will find they save more than others.
Debenham adds that the Fits scheme is "great, but only if you can afford the capital. There is no government-supported scheme for those without the money."
Jon Kimber, the managing director of British Gas New Energy, said: "Solar power will revolutionise the way British homes generate and use energy. Customers [will] reap the benefits of this technology to cut their electricity bills, reduce their carbon footprint and earn a yearly income."
A recent Guardian Money investigation found that it makes financial sense to install the panels yourself. Current remortgaging rates are no more than around 5%-6%, and often lower, but even if you end up paying 12% interest you will still make a huge profit. Most calculations suggest buyers will be able to pay off the costs after nine to 10 years, depending on how much they pay for finance. Most households will make a risk-free profit of £20,000 over the 25 years while enjoying lower electricity bills.
If you are buying the panels upfront, check they come with a warranty. And if you do opt for free solar panels, make sure you get them from a reputable company as you will likely enter into a long-term contract.
Debenham says that, while savings are clearly the incentive with the Fits solar schemes, if consumers install the panels themselves, they will begin to see the green benefits. "It changes forever your relationship with electricity and energy because you can see the impact it has on your bills and how much electricity different things consume. It can teach you to conserve energy."