Renewable energy powering computers

I’ve just been looking at my electricity bill, and it’s enormous. All the computers we have running here are no doubt one of the primary factors. So I’m looking at ways to reduce the cost. The problem is that the main PC is running flat out (100% CPU use) for 12 – 14 hours per day, as it’s helping to cure the world’s diseases as part of the World Community Grid. I’d like to run more computers on the grid and contribute further – I have a laptop sitting idle that could be put to good use. But I don’t want to increase the electricity bill.

I’m sure there must be other ways of powering computers, such as solar panels, wind turbines, water wheels, fuel cells, and whatever else. If you’re powering your computer equipment (or any other electrical equipment) via a renewable energy source or you’ve found a source of low-cost electricity, please get in touch. I’d be particularly interested in the cost of installing the alternative power source versus the cost of electricity saved – i.e. how long does it take to pay for itself? If it was something you built yourself then even better!