Buzz
As we face a period of economic strain, things seem to be getting more expensive. Wages aren’t growing at the same pace, and old money-saving tips are resurfacing. But what if you’ve already cut back and still need a bit more savings? One tried-and-true piece of advice is to turn off lights when you’re not using them. It seems like common sense: You’re paying for electricity, so switching off what you don’t need should help. But could it be that the new, energy-efficient light bulbs we’ve adopted in recent years might make the effort unnecessary? Is walking through a dimly lit home really worth the savings?
The answer isn’t simple. Let’s break down just how much you can actually save by turning off the lights.
You’ll need to do a bit of math.
Now, let’s do some math the old-school way. To begin, you’ll need two numbers: the wattage of your light bulb and your electricity rate. You can find the wattage on the bulb or its packaging. Then, you’ll convert watts into kilowatt hours (kWh). For example, if your bulb uses 13 watts, multiply the wattage (13) by the number of hours it’s been on, and then divide by 1,000. If the light has been on for one hour, the equation looks like this:
(13 * 1) / 1000 = 0.013 kWh
Great, we’ve got the math part down! Next, check your electric bill to see how much you’re paying per kWh. If you need help finding that number, you can check out some sample electric bills here. Now, multiply your rate by the kWh you just calculated. If your rate is 10 cents per kWh, running the lightbulb for an hour will cost 0.0013 cents—less than a penny. If your rate is 20 cents per kWh, you’ll be paying 0.0026 cents.
That doesn’t add up to much. If you’re wondering, at 10 cents per kWh, keeping the light on for 24 hours straight would cost only 3 cents. Of course, less efficient bulbs like a 100-watt incandescent bulb will cost more to run for 24 hours.
It’s still not a lot of money, but let’s think about your entire situation. How many lights do you leave on each day, and for how long? Let’s assume you have 10 lights that are typically on for eight hours at a time during the evening. Half of them are 9-watt bulbs and the other half are 13-watt bulbs, and you’re paying 10 cents per kWh.
(13 * 8) / 1000 = 0.104 kWh, which costs $0.0104 per day. Multiply that by 5 days and you get $0.052
(9 * 8) / 1000 = 0.072 kWh, which costs $0.0072 per day. Multiply that by 5 days and you get $0.036
So, you’re spending around 9 cents daily to keep your house lit. If you do this for 50 weeks a year (ignoring Daylight Savings Time), your annual cost will be approximately $31. Is it worth the effort to go around turning off the lights?
You may be thinking about whether the cost of replacing bulbs affects the equation, especially since you’re running them for 8 hours daily. While it’s true that constantly using LED bulbs will reduce their lifespan, they still typically last for years, even with continuous use. The cost of replacing them will be minimal, especially since you can get LED bulbs for just over a dollar each.
Other factors to consider in calculating your lighting costs
Here are some additional considerations for saving power and money through light bulb management:
CFL: While the math for compact fluorescent light (CFL) bulbs remains the same, their design causes them to react differently to being switched on and off. Turning a CFL on and off frequently can shorten its lifespan significantly. A general rule of thumb is this: If you’ll need the light again within 15 minutes, leave it on. If it’ll be off longer than that, go ahead and turn it off.
Incandescent: This demonstrates why it’s wise to switch away from classic incandescent bulbs. Even the lowest wattage typically found in homes—40 watts—can cost around $112 annually if you run 10 of them for eight hours each day.
The conclusion: Turning off your lights can save some money, but not much. Whether it’s worth the effort really depends on how much you need to save every penny.
