I'm in the process of getting them fitted so have looked into it a lot.
For my roof, I can get 10 panels for around £10,000. You might be able to go for cheaper panels than mine as I have a strange shaped roof so was limited by the size of each panel. Also be aware that some of the more expensive panels are more efficient so you need to balance that out. When you get quotes the companies will give you numbers that you can use for a direct comparison between models, but check them carefully, as there are Government standard figures that they have to give you, and then some of them give you a second set of figures that they say are more typiccal of how the system will work in your specific installation (which might be true) and make their panels look better. It's a bit like comparing MPG on cars - stardard figures for comparison, but the actual performance will be different.
Buying outright is the better option than leasing, as long as you can afford the initial outlay. As with everything, you more money you put in, the better the returns. With leasing, someone else is taking the lion's share of the profit, but leasing is still better than not having panels at all.
Payback on my system is likely to be 8-10 years according to the Government standard figures, but as I have an ideal roof (south coast, directly south facing, no shadow, perfect angle) I am likely to get my money back quicker than that. That's a better return than you will get on the money in any savings scheme.
I think the question is whether you can afford the initial outlay and whether you are likely to stay in the same house for more than 10 years.
Something else to check for - some of the cheaper quotes for the same panels are cheaper because they use a cheaper inverter. The inverter is the part of the system that is most likely to go wrong and is quite expensive to replace. It is also the part of the system that has the most impact on efficency. There is no point having wonderful efficient panels if a lot of the energy is lost in the inverter.
