I've got some friends in California that put solar panels on their house. On a sunny day, they get enough output that they sell power to the utility company.
The down side is that it cost quite a bit, and the panels may lose efficiency before they pay back that cost. There are now newer and more efficient panels that may have better lifetimes - I have no input on that.
It seems a drop in the bucket approach, but enough drops make a difference. I'm not approaching it because of the $20,000 cost.
A class I was in looked into to it. How cost effective it is has a lot to do with where you live which determines how powerful the sun is. In Northern Michigan it would have taken us 70 years to break even (not taking into account that we'll probably be out of oil in 50).
However, Circuit Cellar ran a three-part series on installing a solar system that started in December. You can read it online in their archives for free.
I play around on a small scale, power a few gadgets. The panels are getting bigger, and getting closer to something on a more practical level. About $1500 away from paying off the house, definitely considering getting off the grid. Need to get rid of 5 large oak trees, and I could generate a good amount of power.
There is a big advertising sign in a field beside the road. It had solar power to charge a battery but it didn't light after a cloudy day and didn't light long after a sunny day in winter. So instead of laying expensive electical wiring from a utility pole the owner added a windmill. Now it lights the ad sign for a few hours every night.
The problem is that we haven't found a way to store solar energy.
Wind energy is solar energy, nature's way of storing it.
Solar thermal power is more favoured than solar power, but how long can we store & maintain the temperature of water. Even the most economical solutions out there do not seem economical enough.