Lighting Energy Cost Calculator

Light Bulb Cost Calculator

Estimate the electricity costs of a light bulb or light fixture


Estimate the cost savings and payback period for an upgrade to LED or CFL lamps (optional)


Lighting Energy Cost Estimate:

Using our Lighting Energy Cost Calculator

Find out how much electricity your light fixtures are using and also estimate the monthly cost per light fixture. The lighting energy cost calculator can also estimate how much an upgrade to LED or CFL light bulbs can save you and show the payback time for the upgrade. Simply enter the number of light bulbs, wattage per bulb, approximate daily usage, and your electricity cost per kilowatt hour. We have pre-populated the form with sensible averages, and adjustment to your configuration and costs is simple.

How to Estimate How Much a Light Bulb Costs

Light bulb electricity costs can be calculated by finding the kilowatt-hours a light bulb uses and multiplying by the cost per kilowatt-hour

You can find out how much it costs to keep the lights on by finding the total wattage of your light fixtures, multiplying by the hours the lights are used for and dividing by 1000, then multiplying by the cost per kilowatt hour charged by the electric company. The calculator above can simplify the process, but we’ll go through the formula step by step.

Finding the Total Wattage of Your Lights

Getting the total wattage of your lights that you want to measure energy costs for involves adding the wattage of each bulb/fixture together to get the total. The average A19 incandescent light bulb uses 60 watts of electricity. If you know the wattage of each bulb, simply add the wattages of each bulb together to get the total watts for your lighting system. For example, if you have 5 60w incandescent light bulbs then your total wattage is 300w.

Finding the Energy Your Lights Use

Estimating how much electricity your lights use involves multiplying the total wattage from the previous step by the hours that the lights are on for. If you are trying to find the monthly cost then you need to multiply the wattage by the estimated hours used in the entire month. I find that it’s easiest to estimate how much time the lights are on in a given day and then multiply that by 30.

After you have the total wattage for the time period you need to divide by 1000 to get the kilowatt hours used. For example. If you have 5 60w light bulbs that are used 8 hours per day, your formula looks like this ((5*60) * 8) / 1000, or 2.4.

How Much Does That Electricity Cost?

Every electric company charges a different rate for electricity, and those rates may vary month to month. The national average electric cost is $.12 per kilowatt-hour. You can find your exact rate charged on your electric bill. To find the total cost we need to multiply the kilowatt-hours used that we found in the previous step by the cost per kilowatt hour. Continuing our example the cost would be 2.4 * .12, or $.29 per day or $8.70 per month. That’s almost $9 per month for our 5 light bulbs. Use our electricity cost calculator to estimate the true cost of electricity usage.

How Much Can You Save Upgrading to LED Light Bulbs?

Calculate how much money LED and CFL lamps can save

As you can see an incandescent light bulb costs more than you may have expected. If you multiply that by an entire home full of lights then you can begin to understand how much that costs per month. Enter LED and CFL light fixtures. These light bulbs are becoming very popular for their energy savings and longevity, but they do cost more than an incandescent light fixture. Our energy cost calculator can estimate how long it will take to pay for an LED/CFL upgrade based on the amount of usage, electricity costs, and number of lamps needed.


I prefer to use Philips 60 Watt Equivalent LED light bulbs, as I like the color temperature of the bulbs. LED light bulbs range from very cool and unnatural in color to the warm glow of an incandescent that we have grown accustomed to. The Philips LED bulbs are nice, but other LED can look as good and save as much money so look around.

An average LED light bulb that outputs the equivalent of the 60w incandescent fixture uses roughly 8-9 watts. Upgrading our 5 light bulbs to LEDs using 9 watts of electricity would likely cost $1.30 to power for the month vs the $8.70 of the incandescent lamps. That’s a significant cost savings.

LED lamps last significantly longer then incandescent lamps. This means you save money by not needing to replace light bulbs every year or two. This is not as easy to estimate since light bulbs can last from 6 months to several years, but it’s obvious that over a lifetime an LED or CFL bulb pays for itself purely on replacement cost savings. The average LED bulb lasts 50,000-100,000 hours. A CFL light bulb lasts 25,000 hours on average.