What Uses Watts in Your Home

Electricity usage is calculated in kilowatt-hours. A kilowatt-hour is 1,000 watts used for one hour. As an example, a 100-watt light bulb operating for ten hours would use one kilowatt-hour.

How to calculate electric usage cost:

1. Volts x Amps = Watts
2. Watts รท 1,000 = Kilowatts (kW)
3. Kilowatts (kW) x Hours of Use = Kilowatt Hours (kWh)
4. Kilowatt Hours (kWh) x kWh rate = Cost of Usage
5. Add TVA Power Cost Adjustment charge per kWh

Below are some examples of electrical appliances found in most homes. These examples are using a 10 cents per kWh rate.

Appliance/Equipment Avg. Usage Monthly kWh Cost/Month
Comfort & Health      
Air Conditioner – Window
12,000 BTU (1,400 Watts)
8 hours/day 341 $34.10
Dehumidifier (257 Watts) 12 hours/day 94 $9.40
Fan – Furnace (300 Watts) 7 hours/day 64 $6.40
Fan – Ceiling (125 Watts) 12 hours/day 46 $4.60
Fan – Attic (1000 Watts) 2 hours/day 61 $6.10
Heat Pump (Average Rating)
(1,800 sq. ft. house) 7.7 HSPF*
daily Average Annual Cost $841.50
Heat Pump (High Efficiency)
(1,800 Sq. ft. house) 8.5 HSPF*
daily Average Annual Cost $762.30
Heat Pump (Geothermal)
(1,800 sq. ft. house) Equiv. 13.3 HSPF*
daily Average Annual Cost $487.10
Heater – Portable (1500 W) 8 hours/day 365 $36.50
Humidifier (177 Watts) 8 hours/day 43 $4.30
Water Heater (4500 W) 3 hours/day 411 $41.10
Hair Dryer (1,000 W) 15 min./day 7.6 $0.76
*Heating Season Performance Factor (an efficiency rating)
**Based on 4,296 Heating Degree Days. Cooling costs would be approximately 40% of total energy costs.
Food Prep. & Preservation    
Blender/Food Processor (400 Watts) 1 hour/week 2 $0.20
Coffee Maker (894 Watts) one hour/day 27 $2.70
Dishwasher (1,200 Watts)
(excludes hot water costs)
one hour/day 37 $3.70
Microwave Oven (1,450 W) 30 min./day 22 $2.20
Range (12,200 Watts) 30 min./day 186 $18.60
Freezer 15 Cu. Ft. (341 W.) 12 hrs/day 124 $12.40
Refrigerator – 14 Cu. Ft. (440 W.) 12 hrs/day 161 $16.10
Refrigerator – 18 Cu. Ft.
(manual defrost – deduct 35%)
12 hrs/day 180 $18.00
Laundry      
Clothes Dryer (4,900 W) 6 loads/week 90 $9.00
Washer (512 Watts)
(Excludes water costs)
6 loads/week 9 $.90
Home Entertainment/Recreation    
42″ Plasma TV (320 Watts)
(instant-on tvs use some electricity continuously)
35 hours/week 44.8 $4.48
Home Computer (500 W)
Including Monitor
4 hours/day 61 $6.10
Hot Tub (5,000 W) 2 hrs/day 304 $30.40
Pool Heater (incl. motor) avg/daily 670 $67.00
Pool Pump (1 hp) continuous 1240 $124.00
Lighting      
40-Watt Bulb (40 W)
Equivalent compact fluorescent
4 hours/day
4 hours/day
5
1.375
$.50
$.14
60-Watt Bulb (60 W)
Equivalent compact fluorescent
4 hours/day
4 hours/day
7
1.625
$.70
$.16
75-Watt Bulb (75 W)
Equivalent compact fluorescent
4 hours/day
4 hours/day
9
2.5
$.90
$.25
100-Watt Bulb (100 W)
Equivalent compact fluorescent
4 hours/day
4 hours/day
12
3.25
$1.20
$.33
Farm      
Electric Fence Charger daily 2 $.20
Heater (tractor engine block) (600W) 10 hrs/day 182 $18.20
Heater (livestock tank) 8 hrs/daily 365 $36.50
Auto Battery Charger (600W) 2 hours 36 $3.60
Well Pump (750-1000W) avg./10% usage 40 $4.00

For other tips on saving energy visit the Department of Energy Web site, Energy Savers – Tips on Saving Energy and Money at Home