How Much Do Lights Affect an Electric Bill?

Can you really save money by turning the lights off when you leave a room? The answer depends on what kind of light bulbs you use, how long the lights stay on and how much you pay for electricity. With a simple calculation, you may find that you're already quite efficient when it comes to light bulb use. But perhaps there is still room for improvement.

Before you can calculate the cost of a light bulb, you need to know how much you pay for electricity per kilowatt hour. Check your latest electricity bill to see if it lists the price per kilowatt hour that you pay. If it does not, consider calling your electricity company or looking up your state's average.

The average cost of electricity per kilowatt hour varies depending on your location. In general, electricity tends to be more expensive in New England and along the Pacific and more affordable in the South and Midwest. The national average cost of residential electricity is 13 cents per kilowatt hour.

You can calculate exactly how much money your light bulbs cost you if you know the wattage (which should be printed on the light bulb), how long it stays on and the price per kilowatt hour.

For example: Let's say you have a busy household in which the lights stay on for most of the day. In this example, we'll say that you have five 60-watt bulbs that run from 8 a.m. to 11 p.m.

That gives us 300 watts (5 x 60) running for 15 hours, or 4,500 watt hours. To convert this to the standard kilowatt hour, we need to divide by 1,000. In total, the five 60-watt light bulbs represent 4.5 kilowatt hours each day. Multiplied by the national average cost of electricity, you would spend 59 cents to light your home in a single day. Multiply that by 30 to discover that $17.55 of each month's energy bill goes toward those five light bulbs.

Walk through this example again, but this time replace the numbers with the actual wattage of your light bulbs, with the actual amount you pay per kilowatt hour and with a timeframe that makes sense for your household usage. This exercise should give you an idea of how much light bulbs contribute to your electricity bill.

A lower-watt light bulb costs less to run than a higher-watt bulb. However, lower-watt bulbs tend to give off less light. You may end up putting more lamps or fixtures in a room to light it adequately with lower-watt bulbs, which turns their cost savings into a moot point.

Light bulbs such as LEDs and CFLs earn the moniker "energy saving" because they emit bright light with low wattage. That means they cost less to use but give off light comparable to high-watt counterparts.