Electricity consumption by the computer
Standard office system unit with operating office applications mainly consumes from 250 to 350 watts per hour. A more powerful computer that is running graphics applications and games, respectively, will consume more electricity, for an average of 450 watts per hour. Do not forget about the input devices and output information, which also consume electricity. Modern monitors today use 60 to 100 watt/hour. As for printers and other peripherals, they consume about 10% of the electricity, so they use about 16-17 watt.
The average cost
If you expect the average cost of electricity consumed by personal computer per month, it is enough to multiply the cost for 30 days. For example, if we take the maximum cost of one kilowatt-hour at the Moscow rates, it turns out, about of 3.80 rubles. Thus it appears that if you use a standard office computer to the limit for the entire month and the consumption of electricity from 250-350 watt/hour cost per month 950-1330 rubles (if to use the computer more than 8 hours daily, every month). Gaming computer, respectively, will consume much more electricity, therefore, and money to use such a device to spend more. Of course, the final quantity of electricity consumed depends on how much time you will use the computer and under what conditions.