"Until recently the expense of putting solar panels on the roof meant only a few eco-warriors with money were doing it. Anyone else concluded that the payback period was too long. But solar power, if you will pardon the phrase, is fast coming in from the cold. Sure, the payback time is still long, at 15 years or more. But the annual savings on electricity or gas bills ... is now at least as good, if not better, than sticking spare cash in a building society." (Quoted from article)