Originally posted by: homestarmy
According to my calculations, with a kWh costing 9.879 cents in my area, you are saving about 46 cents a month. Let's say you bought that PSU from newegg and you got the 380w model. That would mean that it will pay itself off in only 15.6 years!
Unless you went with the 430w model, it'll take about 19.2 years. Let's hope they last long enough to make the investment pay off.
I believe you slipped up. So for arithmetic fans here's my take:
Lets figure something simple first, then adjust in proportion.
30 days times 24 hours gives 720 hours in a month (in case something is on 24/7)
100 watts, as for a 100 watt light, gives
720 times 100 = 72000 watt hours or 72 killowatt hours
10 cents a killowatt hour gives $7.20
That gives you somethng to base the rest on.
If you only use 50 watts, that's multiplying by .5 for
.5 x $7.20 = $3.60.
And that's roughly what you save a month for something that saves 50 watts and is on 24/7. If its on 8 hours a day, it's $1.20.
9.879 instead of 10 cents gives
.9879 x $3.60 = $3.56
You can check my arithmetic.
IAC, something that is on a large part of a day, and saves 50 watts can be worth on the order of 12 X $3.60 = $43.20 in savings a year. It is probably more than you imagine, but the key is how much time per day it is on. If it is on only 8 hours, or 1/3 of the day, you are down to $14.40 a year.
A power supply rated at 500 W does not use 500 W, it outputs at most 500 watts. Since an 80% efficient PS is pretty efficient, it would use 500/.80 = 625 watts at max output. But a realistic power use for heavy duty gaming system is probably under 200 W averaged, and the PS would draw less also. (Big PSs are used, I gather, on the theory that they handle peaks better.) But then power supplies used at a fraction of their output don't approach their rated efficiency either. But then PS specs are usually a total load of BS anyway. Without measuring, you have no idea what you are using.