LED Savings Calculator
Yearly dollars and kWh saved by swapping bulbs to LED.
What it does
A bulb swap is the shortest payback in the house. A 60 W incandescent and a 9 W LED give the same 800 lumens, yet the LED draws one seventh of the power. At three hours a day that gap is 55.8 kWh a year per bulb, worth $8.38 at $0.15 per kWh.
The tool above prices any swap. Enter old and new watts, daily hours, rate, and bulb count. It prints yearly dollars first, then yearly kWh and monthly savings, with the old and new loads in the note for a sanity check. Ten bulbs on five hours a day at $0.20 save $186.15 a year.
Federal guides back the watt pairs. The DOE maps 800 lumens to 60 W versus 5.9 to 10.5 W LED, and the FTC notes the same 800 lumen point at about 9 W LED. Energy Star certification marks bulbs meeting EPA and DOE efficiency standards.
Hours decide the prize. A closet bulb burning 30 minutes a day saves little, while kitchen and living room bulbs on five hours carry the house total. Match lumens first so rooms stay as bright, then count the long hour bulbs for the first swap round.
How to use
- Enter the old bulb watts.
- Enter the replacement LED watts for equal lumens.
- Enter daily burn hours.
- Enter your rate per kWh.
- Enter the bulb count on that schedule.
- Read yearly dollars first, then kWh and monthly savings.
Formula
- old W
- Old bulb watts, often 40, 60, 75, or 100.
- new W
- LED watts for equal lumens, often 6, 9, 11, or 15.
- hours
- Daily burn hours per bulb.
- rate
- Electricity price in dollars per kWh.
Watt steps follow DOE lumen tables: 800 lumens maps 60 W to 5.9 to 10.5 W LED. Hours and rate are the levers; bulbs scale the total.
Worked example
Example: 60 W bulb to 9 W LED
Defaults: 60 W to 9 W, 3 hours daily, $0.15 per kWh, 1 bulb.
- Inputs: one 60 W bulb to 9 W LED, 3 hours a day, $0.15 per kWh.
- Old yearly: 60 x 3 x 365 / 1000 = 65.7 kWh, costing $9.86.
- New yearly: 9 x 3 x 365 / 1000 = 9.9 kWh, costing $1.48.
- Savings: 65.7 minus 9.9 = 55.8 kWh, worth $8.38 a year.
- Monthly: $8.38 / 12 = $0.70. Tool shows $8.38, 55.8 kWh/yr, $0.70 /mo.
Reference table
| Light | Old bulb | LED |
|---|---|---|
| 450 lm | 40 W | 4.5 to 7 W |
| 800 lm | 60 W | 5.9 to 10.5 W |
| 1100 lm | 75 W | 9.5 to 14 W |
| 1600 lm | 100 W | 10.5 to 18 W |
Limits
- Energy math only. Light quality and dimmer fit need checking.
- Assumes steady hours; seasonal use shifts results.
- Ignores purchase price; payback needs the bulb premium.
- Rate held flat; tiered and time of use tariffs vary.
Common mistakes
- Matching watts instead of lumens and dimming the room.
- Counting closet bulbs with the same hours as kitchen ones.
- Using a national rate instead of the bill rate.
- Forgetting dimmer compatibility on the LED pick.
- Skipping the long hour bulbs first.
Try it yourself
Quick checks. Answers sit tucked under each question.
100 W to 15 W, 4 hours, $0.12?
Gap 85 W. 85 x 4 x 365 / 1000 = 124.1 kWh. Dollars 124.1 x 0.12 = $14.89.
Ten bulbs 60 to 9 W, 5 hours, $0.20?
Per bulb 51 x 5 x 365 / 1000 = 93.075 kWh = $18.62. Ten bulbs: 930.8 kWh, $186.15.
Questions
Which swap is the standard example?
An 800 lumen bulb: 60 W incandescent versus about 9 W LED, inside the DOE 5.9 to 10.5 W range. Both give the same light.
How much does one bulb save a year?
About 55.8 kWh and $8.38 per bulb at 3 hours a day and $0.15 per kWh. Ten bulbs save $83.80 on the same schedule.
How do I scale to the whole house?
Multiply by bulb count. Hours and rate stay the same; energy and dollars scale linearly with bulbs.
How long do the bulbs last?
Roughly 1,000 hours for incandescent versus 15,000 or more for LED. Fewer replacements add to the savings.
What rate should I enter?
Check the bill or the utility site. US rates often sit near $0.12 to $0.25 per kWh; the default $0.15 edits freely.
How fast is payback?
Divide the extra purchase cost by monthly savings. A $3 premium against $0.70 a month pays back in about 4 months.