Should I turn off fluorescent lights when leaving a room?

It’s an urban myth that turning on and off fluorescent lights uses more energy than just leaving them on. (Photo by Katie Jacewicz.)

It’s an urban myth that turning on and off fluorescent lights uses more energy than just leaving them on. (Photo by Katie Jacewicz.)

Dear Angie: Some of my physician co-workers in the radiology department at the hospital leave the overhead fluorescent lights on in their administrative offices all day, even though they spend 90 percent of their time away from these offices working with patients, reading scans, etc. I have heard that it uses more energy to turn the lights on and off a few times a day than just to leave them on all day. I find that very hard to believe. I wish they would turn off the lights when they leave their offices. What are your thoughts? – Scott S., Lexington, Ky.

Dear Scott: Tell your co-workers it’s time to turn off the lights. It’s been a longtime urban myth that turning on and off fluorescent lights uses more energy than just leaving them on. In fact, the Electric Power Research Institute debunked the notion with a study that revealed it only makes sense to leave the lights on if someone is only leaving the room for three to five minutes. The reason for this is because the electronic ballasts and lamp combination draw a higher level of current at startup (when you turn the light on), but this additional energy only lasts for a fraction of a second.

Turning a light on and off frequently would certainly reduce its life and use a lot of energy, but so does leaving the light on all day. If someone leaves the room longer than those few minutes, it is more cost-effective to turn the lights off.

One way you could try to manage this situation without interoffice conflict is to install motion sensor light switches. Motion sensor lights can be customized to the users’ requirements. When people leave the office, the lights will go off after a certain period of time. Some manufacturers have made switches that allow the user to define how long that lag period is.

There are two common types of sensors: An occupancy sensor detects when someone enters a room and can turn on the lights at that time and then turn them off after the room is vacant. Though occupancy sensors can actually reduce the lamp life as measured in total hours because they do power on and off more frequently, they will extend the overall life in terms of replacement because the lamps operate only during the times they are needed and the energy savings will ultimately outweigh the replacement costs. Vacancy sensors detect only when the room is vacant and will automatically power off the lights after the designated lag time.

Often, these sensors can be installed in the space of the existing light switch with minimal investment. Most sensors cost about $30, but the energy savings will quickly offset that cost.

Another option is to ask your facility manager to contact your local utility for an energy audit, or to hire an independent auditor. Energy auditors can determine ways the facility is wasting energy and provide solutions to reduce energy use. You can also check into groups that work specifically with health care organizations on minimizing their environmental footprint.

Angie’s List collects about 65,000 consumer reviews each month covering more than 550 home and health services. Angie Hicks compiles the best advice from the most highly rated service pros on Angie’s List to answer your questions. Ask Angie your question at


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