Wattage X Hours Used Per
Day ----------------------------------- 1,000 |
= daily kilowatt-hour (kWh) consumption (1 kilowatt = 1,000 Watts) |

For example:

- Window fan: 200 Watts x 4 hours/day, 120 days/year = 96 kWh x 8.5 Cents/kWh = $8.16 /year.
- Clothes dryer: 5,000 Watts x 2 hours/day, 48 days/year = 480 kWh x 8.5 Cents/kWh = $40.80/year.

You can usually find the wattage of most appliances stamped on the bottom or back of the appliance, or on its "nameplate." The wattage listed is the maximum power drawn by the appliance. Since many appliances have a range of settings (for example, the volume on a radio), the actual amount of power consumed depends on the setting used at any one time.

Refrigerators, although turned "on" all the time, actually cycle on and off at a rate that depends on a number of factors. These factors include how well it is insulated, room temperature, freezer temperature, how often the door is opened, if the coils are clean, if it is defrosted regularly, and the condition of the door seals. To get an approximate figure for the number of hours that a refrigerator actually operates at its maximum wattage, divide the total time the refrigerator is plugged in by three.

If the wattage is not listed on the appliance, you can still estimate it by finding the current draw (in amps) and multiplying that by the voltage used by the appliance. (Most appliances in the United States use 120 volts. Larger appliances-clothes dryers, electric cooktops-use 240 volts.) The amps might be stamped on the unit in place of the wattage. If not, find a clamp-on ammeter-an electrician's tool that clamps around one of the two wires on the appliance-to measure the current flowing through it. You can obtain this type of ammeter in stores that sell electrical and electronic equipment. Take a reading while the device is running; this is the actual amount of current being used at that instant.

Note: When measuring the current drawn by a motor, in the first second that the motor starts, the meter will show about three times the current than when it is running smoothly. Contact EREC if you would like to know more about this.

The following are typical annual kWh consumption levels for some appliances. To determine your annual cost of operating one of these appliances, multiply the kWh/year on the table by your electric rate. The running time and wattage in this table are estimates. Your actual consumption will probably vary. Also note that many appliances continue to draw power when they are switched off. These "phantom loads," occur in most appliances that use electricity, such as VCRs, televisions, computers, and kitchen appliances. Most phantom loads will increase the appliance's energy consumption a few watts.

Appliance | Time in use | kWh / year |
---|---|---|

Aquarium | 24 hours / day | 700 |

Iron | 1 hour/week | 52 |

Clock radio | 24 hours / day | 44 |

Microwave oven | 2.hours/week | 89 |

Coffee maker | 30 minute / day | 128 |

Radio (stereo) | 2 hours / day | 73 |

Clothes washer (does not include hot water) |
2 hours / Week | 31 |

Refrigerator (frostfree 16 cubic feet) |
24 hours / day | 642 |

Dishwasher (does not include hot water) |
1 hour / day | 432 |

Refrigerator (frostfree 18 cubic feet) |
24 hours / day | 683 |

Dehumidifier | 12 hours / day | 700 |

Television (color) | 4 hours / day | 292 |

Electric blanket | 8 hrs / day,120days / yr | 175 |

Toaster oven | 1 hour / day | 73 |

Fan (window) | 4 hrs / day,180days / yr | 144 |

VCR | 4 hours / day | 30 |

Fan (furnace) | 12 hrs / day,120 days / yr | 432 |

Vacuum cleaner | 1 hour / week | 38 |

Fan (whole house) | 4hrs / day, 120 days / yr | 270 |

Water heater (40 gallon) | 2 hrs / day | 2190 |

Hair dryer | 15 minutes / day | 100 |

Water pump (deep well) | 2 hrs / day | 730 |

Heater (portable) | 3 hours / day,120 days / yr | 540 |

Water bed (no cover) | 12 hrs / day,180 days / yr | 620 |

Your interest in energy efficiency and renewable energy is greatly appreciated. If we can be of further assistance, please feel free to contact us again.

EREC is operated by NCI Information Systems, Inc. for the National Renewable Energy Laboratory/U.S. Department of Energy. The statements contained herein are based on information known to EREC at the time of printing. No recommendations or endorsement of any product or service is implied if mentioned by EREC.

Energy Efficiency and Renewable Energy Clearinghouse (EREC)

P.O. Box 3048
Merrifield, VA 22116

Voice: 1-800-DOE-EREC

E-mail: doe.erec@nciinc.com