Thanks for the interesting question dorky, even though I'm not sure why it's on the Video forum.. I guess because video cards are the big power hogs in high-end PCs?
My answer is ~$20/month on average, since most of my electricity usage is cooking/fridge/PC/a few CFL lamps, and I don't leave my stuff on 24/7 and rarely turn on the AC/heater.
Your answer depends on if your utility does tiering or not and if you're close to getting bumped up to the next tier.
For instance, PG&E has tiering in order to promote energy efficiency by rewarding low usage and punishing high usage. Everyone starts off using Tier 1 allotments of energy. The allotment size is calculated depending on where you live in the state and how large of a family you have and stuff like that. As long as you stay within that allotment, you pay something like $0.12/kWh (including taxes). Any usage after your Tier 1 allotment bumps you to Tier 2, where you pay more, and after you use up your Tier 2 allotment, you pay even more, etc. until you use up your entire Tier 1, 2, 3, and 4 allotment, in which case you are at Tier 5 and get to pay something like $0.48/kWh.
In addition to the cost of power (and the taxes) above, PG&E charges flat rate connection fees that you would have to pay even if you used zero energy that month. But it's not a big amount.
As a rule of thumb, then, for PG&E customers that stay within Tier 1, every watt at idle costs ~$1.05 per year to run (at-the-wall watts; so more like ~$1.31 for 80+). So if a system draws 100 watts idle, expect to pay $105/year for it. Keep in mind this assumes 24/7 usage, and only idle load, not anything else.
If you want a finer-grained analysis:
1. Take the idle power of your system in watts, divide by 1000, and multiply by 19.5. This is your idle load each day in kWh.
2. Take the full-load power of your system in watts, divide by 1000, and multiply by 4.5. This is your gaming load each day in kWh.
3. Add the two numbers together. This is your total kWh usage each day.
4. Multiply this number by the cost per kWh you pay. (In my example with PG&E Tier 1 rates, it's $0.12/kWh.) This is your daily electrical cost for your PC.
5. You can multiply this by 365 if you want to figure out your annual bill.
NOTE: All calculations above assume at-the-wall watts; if you only know your PC component wattage and have a 80+ rated PSU, then just multiply by 1.25. If you have a 80+ bronze PSU, multiply by 1.2 instead of 1.25. If you have 80+ silver, multiply by 1.15. If you have 80+ gold, multiply by 1.11. Why? Because PSUs are not 100% efficient, so your computer components may only be using, say, 100 watts, but an 80%-efficient PSU needs to pull 125 watts from the wall in order to feed your computer. (0.80 * 125 = 100)
Yes I know this is an oversimplification because PSUs are more efficient at 50% load and less efficient at lower or higher loads. But most people probably spend most of their PC time idling (surfing the web, posting on forums, etc.) which is way the hell down there in terms of power draw, meaning likely only ~80% efficiency. And even at 50% load, most 80+ PSUs are no more than ~85% efficient. It gets better as you go from bronze to silver to gold:
http://en.wikipedia.org/wiki/80_PLUS
Highly efficient PSUs cost more, but pay for themselves over time for heavy users. Ditto with more-efficient CPUs, GPUs, etc. If you are interested in seeing a list of 80+/bronze/silver/gold PSUs, try this link:
http://www.80plus.org/manu/psu/psu_join.aspx
Frankly I am surprised there is not a sticky for this topic.
I didnt worry about my power bill due to living in military quarters. I have about 1 year left on my contract so after my contract ends ill live outside and will have to pay my utilities
currently running
athlon ii x635
3 hd
1 dvdrw
gtx260 in sli
3 x 21.5 inch monitors. 45w per monitor
right now my computer and monitors are on 24/7
how much power bill do i expect if i play game 4-5 hr per day?
I might have to sell everything and get gaming laptop if it helps