It depends on the country you live in, too. In France, they have loads of clean(ish) nuclear power. In Wales, they have a hydroelectric power storage system, that stores power for peak usage. There are similar systems in other locations: http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity

But then - few first world electricity grids are as old and flaky as the US grid.

Yes, how true but when the utility company wants to do something, it's the "Not in My Backyard" attitude of the surrounding communities that shut down these projects. I even called the utility company and told them they could put up a few small windmills in my yard. So far, no response.

Substainable development being in many thoughts nowadays I often asked myself the amount of extra energy wcg is responsible for. Not saying this to put a brake on people participating as I don't think it relevant on a personnal scale. But all this people leaving their computer on 24h active in computing instead of being iddle or off must have an impact speaking of 155 years a day.

I'm not good enough in math to make the evaluation even if it can't be other than an evaluation due to heterogeneousness of each unit participating. I'm sure some of you out there can help in giving us an idea of what it represents. Then converting it into money with average energy price could make us realize it has a real strengh that could be used.

So many people don't even know about grid processing some publicity would be appreciated to reach them and it could be of power supplyer interest to do it.

In the US, nearly 50% of electricity comes from coal and that figure has stayed almost constant for decades. While it's true that coal fired plants have drastically reduced output of sulfur compounds that lead to acid rain, I don't know how well they're doing at reducing CO2 - probably not well at all since the EPA had to be sued in order to get a determination from the US Supreme court that they had the authority to regulate CO2 emissions. Obviously the Bush buffoons don't think it's worth looking into. I don't know to what extent human production of CO2 is a real problem. High levels do seem to be associated with a warmer climate. But there other more potent greenhouse gases that no one is talking about - such as methane, which if my memory serves me correctly is about 10 times more potent as a greenhouse gas than CO2. Also I don't know to what extent the problem would be self limiting. Warmer temps for example could mean more cloud cover which would mean more radiation being reflected back into space. Also, some plant life might become more robust with higher levels of CO2 which would result in a higher percentage being removed from the atmosphere.

On the other side of the coin, there are a lot of unknowns with grid computing. Since we can't be certain that the results of our calculations necessarily reflect how things work in the real world, those results have to undergo experimental testing. We are sort of a prescreening tool. And that is a value function if later testing validates our conclusions. But at this point I think it is still open to debate.

But to put things into perspective, driving the average car one mile puts nearly a pound of CO2 into the atmosphere. Generating 1 kilowatt hour of electricity using coal or oil generates about 2 lbs of CO2 (CO2 payback - page 12).

Based on 1999 data (Internet energy usage), a personal computer uses about 2.67 kw hours per year. Considering the fact that the average power supply for a computer is now 400-500watts rather than 300 watts 10 years ago, we can assume that the true figure for a PC in constant use, even with a flat screen monitor, is probably higher. So let's be conservative and assume it's 3kw hours per year. That would translate to about 6 pounds of CO2.

So, if you want to run one PC guilt free for one year, all you have to do is walk 6 miles per year per PC in instances where otherwise you would have driven your car.

edit - fix typos.

You're reading it wrong, twilyth. The figures are for all PCs in the US, in TWh/year.

Also, power supply ratings don't match the draw on them - modern computers are usually more efficient, and have better power saving.

Computers have a very wide range of power ratings, but 100W is as good an estimate as any. That's 876 kWh per year. Where WCG win is that the difference between a computer on doing nothing and a computer working flat out isn't usually very much.