In these days where electricity is seen by the government as a great source of tax collection, so resulting in price rises, it is worthwhile looking at the power your computers are consuming.
As a first-level approximation assuming a reasonably typical cost of about 34.5 cents for 1 kWh as a computer typically uses about 250 Watts an hour, about 10 hours a day Mon to Sat and 4 hours on Sunday say 64 hours over a year, we are looking at about $300/year just in electricity. Have a monitor, a few other devices and a printer, $1,000 a year is a reasonable estimate per computer per year.
To reduce the costs, you can turn off devices if possible that are not in use. If you are not using much the printer, ask yourself, why is it on?
Older computer equipment uses a lot more power than modern ones; for example, the old CRT monitors use several times as much energy as the modern flat-panel displays.
There are many energy setting on the computer which are worth looking into, one in particular I recommend is to stop people accidentally forgetting to turn off a computer at night change the setting so that the computer shuts down automatically say at 11 pm each night.
Make a switch off button that turns everything off; it is much easier for someone to remember to turn off all the unrequired computer equipment.