It's totally a job for government, a change in the building codes would do it (as suggested above), then the costs would slowly come down, and in time actually become cost effective.

I think seat belts are a great example of this, it's a no briner, they are a great idea, but people didn't just automatically adopt them. It took legislation and each car coming with them fitted from new. Over time we don't even think of it.

I don't think it makes sense everywhere, the UK for example is not a great place for Solar, but in counties like Mexico the government would actually do themselves a favour, they wouldn't need so many power stations ???

Cheers

Cris