How Long Can You Leave Lights On? [Average Cost & Home Safety]

how much money does leaving a light on cost

How many kWh does a light bulb consume? Not much, you might say. So who can blame you if you are leaving lights on whenever you’re in a rush? It’s not as if you left an electricity hog, like the AC unit, running while you’re away on vacation, right? 

Still, lighting fixtures consume energy, and the kWh adds to your home’s total energy usage. So if you constantly leave the lights on, don’t be surprised to find that your electricity bill has risen significantly. And that’s wasted energy, mind you. Let’s see how big a deal it is if you keep leaving the lights on in your home. 

Leaving the Lights On, What Will Happen?

Lights that keep on burning will consume electricity. As such, leaving even just a few lights on can add to your electricity costs. But that’s not the only expense you need to worry about. Keeping the lights on can shorten their operating life.  

The Electricity Consumption of Different Lights

Not all light bulbs consume the same amount of electricity. Those traditional incandescent bulbs that use the old technology are the costliest to operate. In contrast, LED lights are the most energy-efficient. 

Here’s how each type of bulb rates when it comes to how much energy they use. These bulbs’ brightness equals that of a 60-watt incandescent light. 

Incandescent Bulb

An incandescent bulb is a lighting fixture with a wire filament that glows as it heats up. This lighting option uses the oldest lighting technology. It’s the least efficient among the various illuminating solutions, giving off 90% of the energy it consumes as heat. Only 10% goes to creating light.  

This bulb type uses 0.06 kWh per hour. So keeping it on for 1000 hours will add 60 kWh to your energy usage. With electricity prices pegged at $0.11 per kWh, this comes to $6.60 for every 1000 hours you leave the bulb on. 

Halogen Bulb

Halogen lights use the same technology as their incandescent counterparts, albeit with some improvements. The slight modifications make this bulb type a bit more energy-efficient than an incandescent bulb. Halogens need 25% less energy than incandescents to produce light.  

However, this lighting solution still consumes a significant amount of electricity. Keeping a halogen light on for 1000 hours will cost you $4.73. 

CFL Bulb

CFL bulbs are 75% more energy-efficient than incandescent lights. You only add approximately $1.65 to your electric bills if you keep this bulb type on for 1000 hours. However, the on-off operation of a compact fluorescent light can impact its life span. Switching CFLs on and off less often can help make the bulbs last longer. 

LED Bulb

The cost-effectiveness of LED lights is unmatched by other lighting solutions as they are the most energy-efficient among the various lighting fixtures. Thus, using LED bulbs can help increase your energy savings. 

LED bulbs are 80% more efficient than incandescent bulbs, costing only as little as $1.32 to operate for 1000 hours. 

Fluorescent Tube

Fluorescent tubes use a chemical reaction inside the tube or strip to create light. An electric current interacts with the mercury vapor to produce an invisible UV light. The UV light triggers the phosphor coating on the inside of the lamp, causing it to glow.  

Keeping a 32-watt fluorescent tube on for 1000 hours costs around $4.30.  

Average Electricity Cost of Keeping Lights On

As we mentioned, leaving the lights on drives your energy consumption up as your home uses more electricity. But how much electricity you use depends on factors, such as how many lights you keep on, their wattage, and whether you use efficient bulbs. 

Let’s say you use LED lights, the most cost-effective option. Operating a 4.8-watt LED for one hour leads to a 0.0048 kWh addition to your home’s energy usage. Letting it run continuously for 24 hours will add 0.1152 kWh. 

We’re talking only of one bulb. An average home has around 40 light bulbs. So if you turn on all the lights in every room and then leave them on, you’ll need to add up the operating costs of all those light bulbs.  

How to Calculate Lighting Costs?

Knowing how to calculate your lighting expenses can help you determine how to lower your costs. There are two ways to go about this. 

Manual Calculations

Various online calculators exist, but you can try doing the calculations manually and then compare the results with those from online resources. 

  1. Take a look at your monthly electric bill to determine the cost of electricity. Zero in on the total cost, which includes all the charges you pay. 
  2. On your invoice, find the total number of kilowatts used. This indicates how much electricity you consumed 
  3. Multiply the total cost of electricity by the number of kilowatt-hours consumed. You can find the price per kWh on your bill. Otherwise, you can visit your energy provider’s website for information. 
  1. After you’ve figured out the cost per kWh, review the table on your electric bill and search for the one that states the operating cost per watt.
  2. Multiply the operating cost for each watt per year and multiply the answer by the number of watts used by your light fixture. That’s the electricity cost of your lighting solution.

Automated Calculations

If you don’t have a knack for numbers or simply want to quickly determine how much you spend for lighting, you can head on to any website that offers automated calculations for your electricity use. One example is the one found on 

Ways To Lessen Your Lighting Expenses

Lighting accounts for around 10 to 25% of your electric bill. Using these energy-saving tips can help lower your lighting expenses, leaving you some leftover cash from your utility bills. 

Use Energy-Saving Bulbs

A LED bulb is 60% more energy-efficient than a fluorescent light. And while a compact fluorescent lamp is 25-35% more energy-saving than an incandescent bulb, LED lights cut energy use by 75%. So if you keep your lights on for long periods, imagine how much you can lower your energy costs by switching to LED bulbs.  

Utilize Dimmer Lights

Dimmer switches are great not only for helping you set a mood in your living space. Using them is also an excellent way to cut your energy expenses because they reduce the electricity your bulbs use. Not only that, dimmers also increase the life span of some bulb types, which means more savings for you. 

Monitor How Many Hours Your Lights Are On

Turning lights on for extended periods naturally lead to higher power consumption. How much money you spend also depends on the types of bulbs, their wattages, and how many you have. So take note of the number of hours you leave your lights on. Doing so can help you become more conscious of how much energy you can save by switching them off when you don’t need them. 

When Should Lights Be Turned Off to Save Money?

The energy savings you get for switching off the lights depends on what bulb type you use and the per kWh electricity rate in your area. Sometimes, it’s not simply a matter of turning the lights off whenever you leave the house or room. The various bulb types have an operating life that is affected by the number of times the lights get turned on and off. Frequent on-off cycles can lower the life span of most bulbs. 

Incandescent Lighting

Incandescent bulbs waste a significant amount of electricity as they give off 90% of the energy they use as heat. That also leads to another drawback in keeping them on. They add warmth to a room. Incandescents should be turned off when you leave the area to conserve electricity. 

Halogen Lighting

Halogen bulbs use the same technology as incandescent lighting fixtures. They’re just slightly more efficient than incandescents, so they still consume considerable electric power. Also, like incandescents, halogen bulbs emit heat, so turning them off will keep the room cooler. 

CFL Lighting

This is where you’ll have to weigh your options on when to turn the lights on and off. CFL bulbs are energy-efficient, and turning them on and off impacts their life span. As a general rule, leave them on if you’ll be out of the room for only about 15 minutes or so. Otherwise, switch them off. 

LED Lighting

LED lights are the most energy-efficient and cost-effective among the various bulb types. They consume very little electricity, and while turning them on and off won’t affect their life span, leaving them on won’t significantly impact your power consumption. 

Why Do Some People Leave the Lights on All Night?

It usually makes more sense to turn off the lights when you go to bed at night. After all, you won’t need any source of illumination while you sleep. However, some people have reservations about leaving their homes in total darkness. Here are a few reasons why. 

To Have a Better Range of Vision

You can’t predict when you’ll need to suddenly get out of bed at night. By leaving a few lights on, you’ll be able to see your way quickly and won’t have to grope around in the dark. This lessens the risk of injuries like stubbed toes.  

For Security Purposes

Okay, there’s no certainty that burglars won’t hit a brightly lit home. Still, having some illumination can make thieves think twice about entering for fear that someone’s still up and about.  

To Ease Someone’s Fear of the Dark

Not everyone feels comfortable in total darkness. Children, and even adults, are sometimes afraid of the dark. For these individuals, leaving a night light provides a sense of comfort and security. 

Tips on How To Save Electricity

Some techniques will help you save electricity. Let’s take a look at some of them.

  • Replace Frequently Used Light Fixtures with Efficient Bulbs: LEDs are your best bet as they consume the least electricity.  
  • Use Timers To Turn Lights Off: Avoid wasting energy when you or any family member forget to turn the lights off by installing timers. The timer automatically turns the lights off for you. 
  • Make Use of Natural Light (Daylight): Natural light is free. Opening your window blinds or curtains lets you avoid turning on the lights on cloudy days. 
  • Lighter Colors Should Be Used in Decorating: Light colors reflect light, sometimes by as much as 80%. Reflected light reduces your need to use additional lighting. 


Does it cost more to leave a light on or turn it off?

It depends on what bulb type you use. Incandescent and halogen bulbs consume a lot of electricity so turning them off is more cost-effective. Meanwhile, switching CFLs on and off frequently shortens their lifespan. As such, it’s better to keep these light fixtures on if you’ll leave the room for only a few minutes. 

Is it bad to leave lights on for days?

Again, the answer depends on the bulb type. LEDs can be left on for days as they don’t emit heat and aren’t fire hazards. Still, installing a timer is best if you’ll be gone for several days. 

How much does it cost to leave a light on for 24 hours?

A LED light that remains lit for 24 hours will consume about 0.1152 kWh. If the electricity in your area costs around 0.11 per kWh, then that will add $0.012 to your electricity expenses. 

Can leaving a light on at night cause a fire?

Aside from adding to your energy bill, leaving a light on at night is a safety risk. Bulbs can turn extremely hot and ignite flammable materials around them. Tests show that paper wrapped around a 60-watt incandescent bulb can catch fire in approximately 20 minutes. LED lights are safer, but it’s better to turn them off as well. 


It’s easy to overlook turning off the lights, especially when things get hectic. However, if you aim to save electricity and money, every bit helps. Remember, the costs of keeping the lights burning to add up, and that will be wasted electricity if you illuminate an empty house or room. 

You can also avoid turning the lights into fire hazards if you remember to switch them off. So make it a habit to double-check your lighting fixtures before you turn in for the night or leave the house.

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