When I was a kid, I would go around turning off lights that weren’t in use. I’m not sure why I started doing this. These days, it’s a bit of a joke between my mother and me—she’ll turn off the lights in an exaggerated way when she leaves the room.
Of course, there are various reasons for leaving lights on, mostly notably being able to see. It’s also a safety issue—you want to make sure your place looks occupied and ensure the entrance is well-lit when you get home at night. Lights also lend a feeling of comfort and coziness on a dark and dreary day. And chances are, some of the time, you may just forget to turn off the lights or be in a hurry as you head out the door.
Yet we know that leaving lights on unnecessarily wastes energy. Here are some reasons to remember to turn off the lights and tips for changing your habits around lighting.
How much electricity does residential lighting consume?
Lighting makes up a small but significant portion of residential energy use. The U.S. Energy Information Administration (EIA) estimates that, in 2022, residential lighting in the U.S. consumed 67 billion kilowatt-hours of electricity. That accounted for 4% of all residential electricity use and 2% of total U.S. electricity use. The numbers are similar in Canada: lighting accounts for 3.5% of energy use within the home.
A 2012 residential lighting study in the U.S. found that light bulbs were on an average of 1.6 hours a day. Exterior lights tended to be on the longest, with an average of 2.9 hours of daily use. The International Energy Agency notes that, though lighting is becoming more efficient, increased demand has resulted in slight increases in global CO2 emissions and electricity consumption from lights.
The cost of leaving the lights on
In a U.K. study about leaving the lights on, 10% of respondents admitted to leaving the lights on when leaving a room and 21% regularly left them on when leaving the house. This would increase their electricity bill, not to mention waste energy.
ElectricRate.com estimates the cost of leaving different types of light bulbs on. Their estimate is $6.60 for every 1000 hours an incandescent bulb is left on, $1.65 for every 1000 hours a CFL bulb is left on and $1.32 for every 1000 hours an LED bulb is left on (based on all bulbs having a brightness equal to that of a 60-watt incandescent light).
Of course, you’re unlikely to leave a light on for 1000 hours in a row, and the cost will vary based on factors like where you live and the type of bulbs you use. Nonetheless, the numbers give you an idea of the type of costs from leaving lights on.
Tips for turning off the lights
Turning off the lights regularly can be easier said than done, so here are a few tips to help you remember!
- Put a reminder to turn off the lights near light switches or by the front door. This could be a simple sticky note or stickers, like these ones from EcoSchools Canada.
- Open the blinds or curtains to let in natural light instead of turning on the lights. In this way, you’ll also enjoy the health benefits of natural light. However, avoid doing this on very hot days, or you’ll heat up your living space.
- Use lighting controls like dimmer switches, motion sensors and timers to ensure lights are only on as much as they need to be. An important note: always check the light bulb’s instructions before pairing it with a device like a timer or dimmer switch—not all bulbs work with specialized switches. For example, some LED bulbs are not dimmable. Learn more about lighting controls in this article by Energy Saver.
- Try using smart lights that can be controlled using your cell phone in case you forgot to turn off the lights when you left your house or apartment. However, be mindful of accumulating too many of these types of devices since they contribute to digital pollution.
- Participate in Earth Hour in March to join in this global movement of turning off the lights for one hour.
- In a setting like a school or workplace, try running an initiative to turn off the lights on a certain day of the week. For example, in my high school environment club, we ran Lights Off Wednesdays, where we encouraged classes to turn off the lights for an hour on Wednesday afternoons.
When to turn off different kinds of light bulbs
Like just about anything in sustainability, the question of when to turn off the lights is more complicated than it might first appear. According to Energy Saver, incandescent lights should be turned off whenever they’re not needed because they’re extremely inefficient.
CFL bulbs are relatively efficient. Turning them on and off frequently also shortens their operating life. Given that new light bulbs require resources and energy to be produced and transported, Energy Saver recommends only turning off CFL lights if you’ll be out of a room for more than 15 minutes.
The operating life of energy-efficient LED bulbs is not affected by being turned on and off. In that case, it seems to me that you might as well turn off LEDs when you leave a room (though it wouldn’t generate as big energy savings as turning off an incandescent bulb, for example).
A crash course on light bulbs
I don’t know about you, but the few times I’ve gone to buy light bulbs at the hardware store, I’ve been confused by the array of options. So in case you need a refresher on the kind of bulbs you’d most likely be using for a light fixture:
- Incandescent bulbs are the traditional kind, which are generally no longer for sale or hard to find. They give off a warm glow. Though they’re cheap, they have a short life span and are extremely inefficient given that only about 10% of the energy is used for light (the rest is given off as heat).
- Compact fluorescent lamp (CFL) bulbs use up to 75% less energy than incandescent bulbs and last much longer. They’re the ones that are often curvy. They require special disposal because of their mercury content.
- Light-emitting diode (LED) bulbs are extremely energy-efficient. They can reduce energy consumption by up to 90% compared to incandescent bulbs. They’re also durable and long-lasting. Though LEDs tend to be more expensive, their cost has been dropping.
A couple of handy units of measure for light bulbs are lumens and watts. Lumens measure the quantity of light emitted, or brightness. Watts measure the amount of energy that the bulb uses. Different light bulbs require a different wattage to produce the same quantity of light. For example, an LED bulb uses fewer watts to generate 450 lumens than an incandescent bulb would.
A note about safety
When working with light bulbs, always pay attention to what type of bulbs can or cannot be used in a certain light fixture. Read the directions that come with the fixture, and only use the type of bulb recommended for that fixture. For example, CFL bulbs should not be used in enclosed fixtures and, as I mentioned, some LED bulbs cannot be used with dimmer switches. As well, if using a light bulb outdoors, make sure the bulb is approved for outdoor use. Safety comes first!
Beyond turning off the lights
Remembering to turn off the lights when you leave a room is only one part of the energy conservation puzzle. Switching the kind of light bulbs you use may have a bigger impact in the long run.
A 2019 study investigated why turning off the lights remains such a popular energy conservation behaviour, even though it’s less effective than actions like switching to LED light bulbs. The study broke energy-saving behaviours down into two categories: curtailment (low-cost, frequent behaviours like turning off the lights) and efficiency (actions that have a greater upfront cost but result in continuous savings, like switching to LED bulbs).
Based on their survey, the motivation for curtailment actions tends to be social—things like having been taught to turn the lights off as a child, seeing other people do it or feeling guilt. Efficiency actions, meanwhile, tend to involve longer-term thinking, such as a desire to help future generations by saving energy.
Turning lights off and swapping the kind of light bulb represent two different kinds of saving energy. Turning lights off prevents energy from flowing when it’s not being used, while switching light bulbs reduces the energy used when the light’s operating. The good news is that you can do both to maximize energy savings!
Tips for choosing energy-efficient light bulbs
Consider how many lumens of light you will need, then look for the bulb that produces that amount of light using as few watts as possible. As I’ve already alluded to, LED bulbs are the most energy-efficient, followed by CFL bulbs. Look for bulbs certified by ENERGY STAR.
The box will likely also tell you how long the light bulb will last. Where possible, choose the bulb with the longest life span so that you won’t need to change it as often.
Lowering the environmental impact of lighting
Turning off the lights is a small action that we can all take to help the environment. If you also use energy-efficient light bulbs like LEDs, you’ll make great progress on lowering the environmental impact of your lighting.
I want to know: Do you normally turn off the lights when you leave a room?
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