Residential electric bills follow surprisingly uniform patterns from year to year. When a bill is higher than usual, it arouses curiosity. There are many reasons why your use and cost of electric service may vary.

Seasonal Changes

Cold weather requires more heat and use of furnace fans, humidifiers, roof and gutter cables, supplementary heaters, and auto engine heaters. Holiday entertaining requires extra cooking, lighting, and use of Christmas decorations. During hot weather, there is increased usage because of air conditioners, fans, refrigerators, freezers, dehumidifiers, and laundry appliances. The following charts show average use factors for heating and lighting and how they vary seasonally.

It's natural to expect your electric bill to decrease substantially when you're away from home. But while you're away, your refrigerator, freezer, and water heater continue to operate, unless you turn them off. Also, your vacation schedule may not coincide with a billing period. Your reduced usage, therefore, would be spread over two bills. It's likely, too, that you'll use more electric energy getting ready for a vacation and when you return home again.

• Your lifestyle may change, your family grows, you entertain more often, or you have more house guests.
• The age and condition of your appliances often affects their cost of operation.
• You may leave lights or appliances on unnecessarily — wasting electricity and affecting your bill.

Variations are caused by the length of the billing period. In general, for every day's difference in the billing period, your energy consumption increases or decreases 3 percent.

Use our Energy Calculators to figure the energy consumption of typical appliances. These calculators allow you to focus on the energy use of a specific appliance in your home. You will learn how much you can save by installing new, energy-efficient appliances and how to operate them efficiently.

See our Home Energy Saving Tips and Tools