Ask Dr. Bill

Pick new bulbs and calculate your savings.

Posted: 17-Oct-2006; Updated: 09-Jan-2007

Is it better to turn a light on or leave it off?

This is a great question and one that each of us confronts every day. To some extent, the answer depends on the type of bulbs you're using.

Traditional incandescent bulbs are so inefficient, that it really is better to turn them off when they are not needed, even if you're leaving the room for only a few minutes.

However, with compact fluorescent blubs (CFLs) you can be a little more flexible. The amount of energy used to turn lights off and on again - the "inrush" - is typically equal to only a few seconds of normal light operation. So, technically, you're saving energy by turning off CFLs.

But, CFLs are so energy efficient that you're not wasting too much energy by leaving them on if you're only stepping away for just a few minutes.

A common misperception is that it takes a lot of extra energy to turn on a CFL. This may seem true since some CFLs take a few minutes to "warm up" before they reach full brightness. Turning on a light does require additional energy; however, the bulb's "warm up" period does not draw extra electricity.

Rule of thumb: If you know you'll be away for more than a few minutes, you should make a habit of turning off your lights. And, regardless of your habits, you should buy CFLs and install them everywhere. The savings are enormous.

Where can I find a guide that compares compact fluorescents?

Perfect timing! We just completed our brand new light bulb guide that will allow you to compare compact fluorescent bulbs, types of lights and light fixtures, and find the right CFL match for your needs.

Once you've figured out which fluorescent bulbs are right for you, you can calculate how much you'll save by switching 1 or 100 incandescent bulbs to CFLs in your home.