Figure 100 Watts for under 1GHz machines, 200 for above 2GHz. Printers vary widely with my old Laserjet II sucking up 1,000 Watts when the heater element kicks in to today's laser that sips 4 or less Watts when just sitting there.
If the printers/scanners are newer, guesstimate 10 Watts each.
If you feel you don't want to guess, go to Radio Shack and buy the wall mount AC Watt Meter.
I ahve two computers that I leave on continuously. a 667 MHZ HP
and a 2300 MHZ emachine
I also have two printers and a scanner
Anyone know approx. how much energy in kilowatts this would be per month?