How Much Does It Cost To Leave A Light On?

Updated on July 29, 2026 | Written by Alec Pow
This article was researched using 8 sources. See our methodology and corrections policy.

Leaving one light on costs about $0.04 per day for a 9-watt LED bulb or about $0.27 per day for a 60-watt incandescent bulb when both run for 24 hours. At the May 2026 U.S. residential electricity average of 18.44 cents per kilowatt-hour, the same LED costs about $1.19 per month, while the incandescent costs about $7.97 per month.

The cost depends on three numbers: the bulb’s wattage, how many hours it runs, and the electricity rate on the utility bill. Brightness does not determine the bill by itself. Two bulbs can produce roughly the same 800 lumens while drawing 9 watts and 60 watts.

A light left on all night usually costs only a few cents when it uses an efficient LED. The expense becomes more noticeable when a home has many bulbs, older incandescent or halogen lighting, high utility rates, or lights running in unused rooms every day.

Article Highlights

• A 9W LED costs about $0.0017 per hour at the May 2026 national residential electricity rate.
• Leaving that LED on for 24 hours costs about $0.04.
• A 60W incandescent costs about $0.27 per day or $96.92 (at $30 per hour, earning that amount would take about 3.2 hours of work, before taxes) per year when left on continuously.
• Ten 9W LEDs used eight hours daily cost about $48.46 per year.
• Ten 60W incandescent bulbs used for the same time cost about $323.07 per year.
• Replacing those ten incandescent bulbs with LEDs saves a computed $274.61 per year in electricity.
• Smart bulbs can reduce wasted use through schedules and sensors, but they draw a small amount of standby power.

How Much Does It Cost to Leave a Light On?

The U.S. Energy Information Administration reported an average residential electricity price of 18.44 cents per kWh for May 2026. The calculations below use that rate and assume the bulb stays on for 24 hours per day.

Bulb wattage	Cost per hour	Cost per day	Cost per 30-day month	Cost per year
5W LED	$0.0009	$0.02	$0.66	$8.08
9W LED	$0.0017	$0.04	$1.19	$14.54 (about 29 minutes at $30 per hour)
15W LED	$0.0028	$0.07	$1.99	$24.23
40W incandescent	$0.0074	$0.18	$5.31	$64.61
50W halogen	$0.0092	$0.22	$6.64	$80.78
60W incandescent	$0.0111	$0.27	$7.97	$96.92
100W incandescent	$0.0184	$0.44	$13.28	$161.56

Your result can be much lower or higher because residential electricity rates vary by state. The same 9W bulb costs twice as much to operate at $0.30 per kWh as it does at $0.15 per kWh.

Calculate the Cost of Any Light

Use this formula:

Wattage ÷ 1,000 × hours used × electricity price per kWh = operating cost.

For a 9W LED used for eight hours at $0.1844 per kWh:

9 ÷ 1,000 × 8 × $0.1844 = $0.0133 per day.

That is about 1.3 cents per day, $0.40 per month, or $4.85 per year.

For a 60W incandescent used under the same conditions:

60 ÷ 1,000 × 8 × $0.1844 = $0.0885 per day.

That equals about 8.9 cents per day or $32.31 (about 1.1 hours of work at $30 per hour) per year. The incandescent costs roughly $27.46 more per year than the 9W LED for one socket.

What Watts and Lumens Measure

Watts measure electricity use. Lumens measure the amount of visible light produced. A higher-wattage bulb does not always produce more light because different lighting technologies convert electricity into light with different efficiency.

The ENERGY STAR bulb guide uses about 800 lumens as the replacement target for an old 60W standard bulb. A modern LED can provide that brightness while using around 8W to 10W.

Common brightness targets include:

• About 450 lumens to replace a 40W incandescent
• About 800 lumens to replace a 60W incandescent
• About 1,100 lumens to replace a 75W incandescent
• About 1,600 lumens to replace a 100W incandescent

Compare bulbs by lumens first, then select the lowest suitable wattage. Comparing a dim 5W LED with a much brighter 100W incandescent does not show the cost of producing the same amount of light.

LED vs Incandescent Cost

The U.S. Department of Energy reports that LED lighting can use up to 90% less energy and last up to 25 times longer than traditional incandescent bulbs. The exact saving depends on the wattages being compared.

A 9W LED and a 60W incandescent can each produce about 800 lumens. At the current national rate, continuous operation costs:

• 9W LED: $14.54 per year
• 60W incandescent: $96.92 per year
• Difference: $82.38 per year

The LED uses 51 fewer watts, a reduction of 85%. That is a more defensible comparison than saying every LED always uses five, seven, or ten times less electricity.

The cost of buying a bulb is separate from the electricity expense. Full-spectrum, specialty-shape, high-CRI, dimmable, and connected products can cost more than a basic LED. Current full-spectrum light bulb prices illustrate why a low running cost does not always mean a low purchase price.

Ten-Bulb House Calculation

To show the household effect, ThePricer calculated the annual cost of ten bulbs used for eight hours per day at 18.44 cents per kWh.

Ten 9W LEDs consume 90 watts while they are on:

10 × 9W ÷ 1,000 × 8 hours × 365 days × $0.1844 = $48.46 per year.

Ten 60W incandescent bulbs consume 600 watts:

10 × 60W ÷ 1,000 × 8 hours × 365 days × $0.1844 = $323.07 per year.

The computed annual saving is $274.61. Twenty bulbs under the same use pattern would double the saving to about $549.22 per year, not the unsupported $800 estimate in the old article.

This calculation covers electricity only. Buying ten replacement LEDs creates an upfront cost, but even a $30 to $50 bulb purchase could be recovered quickly when the old bulbs truly draw 60 watts each and run eight hours daily.

The Cost of Leaving a Porch Light On

A porch light using a 9W LED for 12 hours each night consumes:

9 ÷ 1,000 × 12 × 365 = 39.42 kWh per year.

At $0.1844 per kWh, the annual electricity cost is about $7.27. A 60W incandescent on the same schedule costs about $48.46 per year.

A dusk-to-dawn sensor can prevent the light from running during daylight. A motion sensor can reduce operating hours further, but it may not suit a location where continuous nighttime visibility is preferred.

Outdoor decorative lighting can create a larger seasonal bill when many strings are used. The purchase and labor costs for Christmas light installation are separate from the electricity needed to run the display.

Smart Bulbs and Standby Power

Smart bulbs are usually LEDs, so their low operating wattage comes from the LED technology rather than the Wi-Fi, Bluetooth, or Zigbee controls. Their schedules, dimming, and occupancy routines may reduce the hours they stay on.

They also draw a small amount of standby electricity while switched off through the app because their radios remain ready to receive commands. Philips Hue says this draw is typically less than 1 watt per bulb. One current 800-lumen Hue bulb is rated at 8.8W while operating and 0.2W in standby.

If that bulb is on for eight hours and in 0.2W standby for 16 hours daily, standby adds only about $0.22 per year at the national rate. Ten such bulbs add about $2.15 per year in standby use.

A smart bulb does not automatically save more electricity than a regular LED. It saves money when automation prevents unnecessary operating time or reduces brightness. Paying $24.99 for the cited smart bulb solely to eliminate a few cents of monthly lighting use may not produce a fast financial payback.

The Bulb’s Purchase

Electricity is only one part of lighting ownership. Bulb lifespan, fixture compatibility, purchase price, and replacement labor can matter, especially in recessed ceilings, stairwells, outdoor fixtures, or hard-to-reach locations.

ENERGY STAR states that certified LED bulbs provide the same brightness with less energy and can last far longer than incandescent products. The cited Philips Hue model carries a nominal rating of 25,000 hours. At three hours per day, that rating represents about 22.8 years, though heat, enclosed fixtures, electronics, switching, and product quality can shorten real service life.

Do not assume every LED lasts 50,000 to 100,000 hours. Product labels commonly show ratings between about 10,000 and 25,000 hours for household bulbs. Check whether the bulb is approved for enclosed fixtures, damp locations, outdoor use, dimmer switches, or ceiling fans.

If a fixture or wiring problem requires professional work, the bulb’s electricity cost may be the smallest part of the project. The cost of installing a chandelier or replacing a fixture includes electrician labor, mounting, access, and possible wiring changes.

The Hidden Cost of Heat

Incandescent and halogen bulbs release much of their input energy as heat. During warm weather, air conditioning may have to remove some of that heat, which creates an indirect cost not shown in the bulb-only formula.

The heating effect can be less wasteful during cold weather, but a light bulb is not an efficient or controlled substitute for a heating system. The practical saving from LEDs remains strongest where lights operate for many hours, electricity is expensive, or cooling runs for much of the year.

Heat can also shorten LED life when bulbs are installed in fixtures that trap warm air. Buying a higher-priced LED and placing it in an incompatible enclosed fixture can erase part of the expected lifetime saving.

Three Realistic Lighting Scenarios

One bedroom lamp: A 9W LED used four hours per day costs about $2.42 per year. Turning it off one hour earlier each night saves only about $0.61 per year.

Ten-light living area: Ten 9W LEDs used six hours daily cost about $36.35 per year. Replacing them with higher-output 15W LEDs would raise the cost to about $60.58 per year.

Twenty old incandescent bulbs: Twenty 60W bulbs used eight hours daily cost about $646.14 per year. Twenty 9W LEDs under the same conditions cost about $96.92, leaving a computed difference of $549.22.

When Switching Bulbs Pays

Replacement makes financial sense if:

• The existing incandescent or halogen bulbs run for several hours daily.
• The LED replacement produces the same required lumens.
• The fixture accepts the bulb’s shape, base, heat rating, and dimming type.
• Electricity prices are high or the home uses many bulbs.

Immediate replacement may save little if:

• The old bulb is used only a few minutes per day.
• The replacement is an expensive smart or decorative product bought only for energy savings.
• The fixture requires a specialist LED with a high purchase price.
• A working efficient LED is being replaced by another LED with nearly the same wattage.

What We Verified

• Checked the current national residential electricity rate against the EIA’s May 2026 data.
• Confirmed that lumens measure brightness and watts measure energy use through ENERGY STAR brightness guidance.
• Cross-referenced LED energy and lifespan claims with Department of Energy lighting guidance.
• Verified smart-bulb standby use through Philips Hue’s power explanation.
• Confirmed that state electricity prices vary widely through the EIA’s state residential rate table.

Answers to Common Questions

How much does it cost to leave an LED light on all day?

A 9W LED costs about $0.04 for 24 hours at an electricity rate of 18.44 cents per kWh.

How much does it cost to leave a light on overnight?

A 9W LED left on for 12 hours costs about $0.02. A 60W incandescent costs about $0.13 for the same period.

Does turning lights off save much money?

It saves little for one LED used briefly, but the saving grows across many bulbs and many hours. Turning off ten 9W LEDs for four unnecessary hours daily saves about $24.23 per year.

Are smart bulbs cheaper to run?

They use efficient LED technology but draw a small standby load. They cost less only when schedules, sensors, or dimming reduce enough operating time to offset that standby use and their higher purchase price.

What is the cheapest bulb to leave on?

Among bulbs producing similar brightness, the one with the lowest wattage costs the least to run. For an 800-lumen household bulb, an efficient LED near 8W to 10W is much cheaper to operate than a 60W incandescent.