Answer
Until the cost of solar energy drops to the point where it is economically viable to choose it over power from the grid, solar power will remain unusual. The problem is that for solar power, you need to committ large amounts of money during the building phase. Tens of thousands of additional dollars, and space for expensive batteries that have a limited lifetime. What is truly needed is advances in battery technology. Unfortunately chemistry is fairly well understood, and there don't seem to be any useful candidates for really efficient and cheap batteries. As for numbers, the definition of solar is vague: there are active, passibe, and combination systems. And the degree to which house can supply power also varies quite a bit.