i was thinking of the same thing on my way to the local reptile shop ,just think the nice sunny day put the idea in my head lol, as i will be building a new reptile/insect room in the garage soon i was thinking of this idea to go on the roof but i couldent find any price on that web site tho
You can probably get them cheaper but, as with pretty much all solar-powered things, it takes a very long time before you recover your costs...
Long-term it would be worthwhile - I expect energy prices are going to rocket in the next decade or two, so you would really feel the benefit of them then.