Basic equations to use for calculating:  

• VOLTS x AMPS = WATTS
• WATTS x TIME = kWh   
• One 100 watt bulb on for ten hours = 1000 watt hours
• 1000 watts x 1 hour = 1 kWh
   

The best way to compare the cost of running different appliances is to look at their power consumption, which is a measure of how much power they use in Watts.

The following list points out typical values for the wattage of some devices you would find in your home so you can compare them for a monthly average.

Another resource is the US Department of Energy's Appliance Energy Calculator

Appliance & Typical Wattage	Average Use	Monthly Avg kWh Use
Heating & Air Conditioning
Window Unit, 9000 Btu/hr	8 hrs/day	321 kWh
Central System, 24,000 Btu/hr	8 hrs/day	857 kWh
Window Fan – 200 watts	2 hrs everyday	14-29 kWh
Furnace or Central Air – 270 watts	7 hrs everyday	59 kWh
Attic Fan	8 hrs everyday	75-150 kWh
Appliances
Clothes Dryer – 4900 watts	6 Loads/week	83 kWh
Clothes Washer (mach.operated) 512 watts	Per Load	3-4 kWh
Blender – 385 Watts	6 times/week	1 kWh
Juicer – 90 watts	Once/day	.05 kWh
Computer and Monitor – 100-200 Watts	4-8 hrs/day	12-48 kWh
Dishwasher – 1200 watts Hot Water for 30 loads	30 loads/month	30 kWh 100-130 kWh
Refrigerator 15 cu. ft. Upright, frost free – 440 watt	Everyday	125-200 kWh
Refrigerator Upright, manual defrost – 341 watts	Everyday	80-140 kWh
Freezer Chest, manual defrost	Everyday	60-100 kWh
Range/Oven 12,200 watts Self-cleaning process	For family of 3 Each use	100 kWh 5 kWh
Microwave Oven	Each day	16-40 kWh
Toaster & broiler/oven	Once/twice a day	4-12 kWh
Color TV, tube-type, 300 watts	6 hrs everyday	55 kWh
Color TV, solid state, 200 watts	6 hrs everyday	37 kWh
Vacuum Cleaner – 650 watts	10 min. everyday	4 kWh
Water Heater – general use	For family of 4	350 kWh
Well pump – 1000 watts		75-130 kWh
Garage Door Opener – 113 HP	4 times per day	.3 kWh