My current processor is a 110W AMD X2 4600+. For fun, I was looking at a 35W Core i3 2100T. Looking around I couldn't find a direct performance comparison anywhere between the two, but it looks like the i3 would actually bring a (very) small performance bump vs the 4600+. The upgrade would also involve a move from 2GB DD2 to 8GB DDR3, so as long as I don't lose too much this will be a win, performance-wise. The price (cpu,mb,and ram) would come to about $310.
I really don't have any budget for upgrades right now, but I was curious: if I were to go ahead and get this, how long would it take for the energy savings to pay for the upgrade? Could I justify the purchase this year on energy savings alone?
I suspect not, and I know it depends on usage and local rates. But I'm hoping to be able to put a ballpark figure together for how much I could save in a year. As a reference, local rates are $.0933/kWhr
I'll start with a basic calculation that uses a few bad assumptions, and we'll see if we can refine it any:
Assuming both systems are running full-capacity, that means I save 75W/hr. I also have to dissipate that energy, so I really save 150W/hr, or .15kWhrs. .15 * .0933 = $.013995 save per hour I run the new system. .013995 * 24hrs/day * 7days/wk * 52wks/year results in $122.26 saved per year. So I'd need to run this for about 2 1/2 years to pay back the investment. And again, that's assuming 100% run all the time and an additional 100% cost for heat, neither of which are very good. Can we get even more accurate numbers?