There are companies out there that will fit a system free of charge provided you have a south facing roof. They will give you a small amount in return usually as a percentage of electric bill. In other words, you are renting out the roof space for a nominal gain.
1. Solar panels are ugly as hell.
2. "free solar panels" means you can use the electricity produced, about £90 a year if you're lucky, plus see point 1. (Also, you cant touch your roof for 25 years).
3. If you buy the solar panels yourself, you get 8% or something "return" but it's not really "return" because once installed, they are worth zero. It's another massive mis-selling scandal. If the govt doesnt tamper with the tariff etc, you will catch up with risk free rates of return around year 16 / 17 of its 25 year tariff "promise".