Answer first
What this calculator tells you
Calculate yearly electricity savings from swapping older bulbs for LEDs. Rank the rooms worth relamping first by how many hours their lights stay on. Formula: Annual kWh saved = (old watts − LED watts) ÷ 1,000 × hours per day × 365 × bulbs; savings = kWh saved × price. At the worked-example inputs, the savings per year is $190. Holding every other input steady, moving electricity price per kwh from $0.14 to $0.20 moves the result from $156 to $223.
Transparent method
The formula
Rank the rooms worth relamping first by how many hours their lights stay on.
Worked example
Example inputs
How to interpret the result
Bulbs save money in proportion to the hours they burn, so the same swap is worth far more in a kitchen than in a closet. Replacing twenty 60 watt bulbs with 9 watt LEDs that run three hours a day saves about 1,117 kilowatt-hours a year, or roughly $190 at 17 cents. The bulbs also last longer, which the electricity math does not count.
At the worked-example inputs the savings per year is $190. It rises with electricity price per kwh, old bulb wattage, hours on per day and number of bulbs and falls as LED bulb wattage increases.
Real energy use depends on how the appliance or vehicle is actually run: duty cycle, weather, driving style, battery age and your utility's rate structure, including tiers and time-of-use pricing. Treat the result as a planning estimate and check it against your own bill or trip log.
Before you rely on it
What to check
Use the hours each bulb really burns, not the hours the room is occupied. Lights left on in empty rooms count against you.
The common error
Where people go wrong with LED bulb savings calculator
Assuming the savings apply to heating months in the same way. In a cold climate the old bulbs also gave off useful heat, which the furnace now has to supply.
Sensitivity evidence
How electricity price per kwh changes the savings per year
Holding every other input at the worked-example value, moving electricity price per kwh from $0.14 to $0.20 moves the savings per year from $156 to $223: a spread of $67, or 35% of the worked-example result.
| Electricity price per kWh | Savings per year | Energy saved per year (kWh) |
|---|---|---|
| $0.14 | $156 | 1,116.9 |
| $0.15 | $168 | 1,116.9 |
| $0.17worked example | $190 | 1,116.9 |
| $0.19 | $212 | 1,116.9 |
| $0.20 | $223 | 1,116.9 |
Every input, tested
Which input moves the savings per year most
Of the 5 inputs, electricity price per kwh moves the savings per year most ($45 across the range tested) and LED bulb wattage moves it least ($7.45).
| Input | Tested from | To | Savings per year at each end | Swing |
|---|---|---|---|---|
| Electricity price per kWh | $0.15 | $0.19 | $168 to $212 | $45 (24%) |
| Old bulb wattage | 54 | 66 | $168 to $212 | $45 (24%) |
| Hours on per day | 2.7 | 3.3 | $171 to $209 | $38 (20%) |
| Number of bulbs | 18 | 22 | $171 to $209 | $38 (20%) |
| LED bulb wattage | 8 | 10 | $194 to $186 | $7.45 (3.9%) |
Two variables at once
Savings per year by electricity price per kwh and old bulb wattage
Across the grid the savings per year runs from $120 to $276. Moving electricity price per kwh from $0.14 to $0.20 shifts it by $67 at the middle column, and moving old bulb wattage from 48 to 72 shifts it by $89 at the middle row, so old bulb wattage is the bigger lever here.
| Electricity price per kWh \ Old bulb wattage | 48 | 60 | 72 |
|---|---|---|---|
| $0.14 | $120 | $156 | $193 |
| $0.15 | $128 | $168 | $207 |
| $0.17 | $145 | $190 | $235 |
| $0.19 | $162 | $212 | $262 |
| $0.20 | $171 | $223 | $276 |
The highlighted cell is the worked example: $190.
Step by step
The worked example, input by input
| Input | Value used | What it means |
|---|---|---|
| Old bulb wattage | 60 | Enter the old bulb wattage used in this calculation. |
| LED bulb wattage | 9 | Enter the LED bulb wattage used in this calculation. |
| Hours on per day | 3 | Enter the hours on per day used in this calculation. |
| Number of bulbs | 20 | Enter the number of bulbs used in this calculation. |
| Electricity price per kWh | $0.17 | Enter the electricity price per kwh used in this calculation. |
| Savings per year | $190 | |
| Energy saved per year (kWh) | 1,116.9 | |
Inputs, definitions and assumptions
Old bulb wattage
Enter the old bulb wattage used in this calculation. The prefilled worked-example value is 60.
LED bulb wattage
Enter the LED bulb wattage used in this calculation. The prefilled worked-example value is 9.
Hours on per day
Enter the hours on per day used in this calculation. The prefilled worked-example value is 3.
Number of bulbs
Enter the number of bulbs used in this calculation. The prefilled worked-example value is 20.
Electricity price per kWh
Enter the electricity price per kwh used in this calculation. The prefilled worked-example value is $0.17.
How to use this calculator
- 1Verify the inputs. Gather old bulb wattage, LED bulb wattage, hours on per day, number of bulbs and electricity price per kwh from your own documents; the prefilled values are examples.
- 2Save a baseline. The worked example puts the savings per year at $190. Store your own version of it as Scenario A.
- 3Test one change. Start with electricity price per kwh, the input with the biggest effect here: moving electricity price per kwh from $0.15 to $0.19 takes the savings per year from $168 to $212, a swing of 24% of the worked-example figure.
- 4Check the extremes. At half the example electricity price per kwh ($0.09) the savings per year is $95; at double ($0.34) it is $380.
People also ask
Frequently asked questions
How do you calculate LED bulb savings?
Annual kWh saved = (old watts − LED watts) ÷ 1,000 × hours per day × 365 × bulbs; savings = kWh saved × price. Enter electricity price per kwh in dollars. At the worked-example inputs the savings per year is $190.
What does the LED bulb savings result mean?
Rank the rooms worth relamping first by how many hours their lights stay on. At the worked-example inputs the savings per year is $190. It rises with electricity price per kwh, old bulb wattage, hours on per day and number of bulbs and falls as LED bulb wattage increases.
How much does electricity price per kwh change the savings per year?
Holding every other input at the worked-example value, moving electricity price per kwh from $0.14 to $0.20 moves the savings per year from $156 to $223, a spread of $67.
What are the limits of this LED bulb savings calculator?
Real energy use depends on how the appliance or vehicle is actually run: duty cycle, weather, driving style, battery age and your utility's rate structure, including tiers and time-of-use pricing. Treat the result as a planning estimate and check it against your own bill or trip log. The tables on this page test electricity price per kwh only from $0.14 to $0.20; a value outside that range is not tabulated here.
Which input moves the savings per year most in the LED bulb savings calculator?
Ranked by how far each moves the savings per year across the range tested: electricity price per kwh ($45, 24%), old bulb wattage ($45, 24%), hours on per day ($38, 20%) and number of bulbs ($38, 20%).
If I double electricity price per kwh in the LED bulb savings calculator, does the savings per year double?
Doubling it from $0.17 to $0.34 takes the savings per year from $190 to $380, which is 2.00 times the worked-example figure. So the result scales almost exactly in proportion. Halving it to $0.09 gives $95.
How much does old bulb wattage matter in the LED bulb savings calculator?
The worked example uses 60. Holding every other input at its worked-example value, moving old bulb wattage from 54 to 66 takes the savings per year from $168 to $212, a swing of 24% of the worked-example figure.
How much does LED bulb wattage matter in the LED bulb savings calculator?
The worked example uses 9. Holding every other input at its worked-example value, moving LED bulb wattage from 8 to 10 takes the savings per year from $194 to $186, a swing of 3.9% of the worked-example figure.
How much does hours on per day matter in the LED bulb savings calculator?
The worked example uses 3. With the other inputs left at the worked example, moving hours on per day from 2.7 to 3.3 takes the savings per year from $171 to $209, a swing of 20% of the worked-example figure.
How much does number of bulbs matter in the LED bulb savings calculator?
The worked example uses 20. Holding every other input at its worked-example value, moving number of bulbs from 18 to 22 takes the savings per year from $171 to $209, a swing of 20% of the worked-example figure.
Which inputs change the energy saved per year (kwh) in the LED bulb savings calculator?
At the worked-example inputs it is 1,116.9. Old bulb wattage takes it from 985.5 to 1,248.3, LED bulb wattage takes it from 1,138.8 to 1,095, hours on per day takes it from 1,005.2 to 1,228.6 and number of bulbs takes it from 1,005.2 to 1,228.6.
Why is standby power worth counting?
Devices left plugged in draw a few watts around the clock. Across a house of chargers, screens and set-top boxes that adds up, and it runs all 8,760 hours of the year.
Do EV efficiency figures include charging losses?
It depends on how the figure was measured, so check the source. The EV calculator lets you add a loss percentage, so the cost reflects what the wall supplies and not only what reaches the battery.
How do I measure my real gas mileage?
Fill the tank, note the odometer, drive normally, then fill again. Miles since the first fill divided by the gallons added is your mileage for that tank. Average a few tanks.
Sources and evidence
Free Calculators Online is independent and is not affiliated with or endorsed by the source organizations. Educational estimates only.