LED Bulb Savings Calculator
Swap incandescent bulbs for LEDs and see exactly what it returns: electricity saved each year, how many months until the bulbs pay for themselves, ten-year savings once avoided replacements are counted, and the carbon that never gets burned.
Your bulbs
Bulb prices & lifespan
How to use this calculator
1. Count the sockets, not the rooms
A single ceiling fixture often holds three or four bulbs, and each one draws its own wattage. Walk the house and count actual bulbs. If some fixtures are already LED, leave them out — this tool compares the ones you would still be swapping.
2. Be honest about hours per day
Hours are the single biggest lever in the whole calculation, bigger than the price of the bulb. A porch light on dusk-to-dawn runs 12 hours; a hallway fixture might run 45 minutes. Use the slider under the chart to see how quickly the payback line moves when you change it.
3. Use your real electricity price
Do not use the headline rate on your utility's website. Divide the bottom-line amount on your bill by the kilowatt-hours it lists — delivery, transmission, and fixed charges pull the true cost per kWh well above the advertised energy rate in many states.
4. Read the crossover, not just the total
The line chart plots what each option has cost you at every point in time. LEDs start higher, because you buy them on day one; incandescents start at zero and then climb steeply on electricity plus a new bulb every time one burns out. Where the two lines cross is the moment the swap has paid for itself. Everything after that is money kept.
LED savings FAQs
How much electricity does swapping one bulb to LED actually save?
Energy saved per year = bulbs × (old watts − new watts) ÷ 1000 × hours per day × 365. That gives kilowatt-hours; multiply by your electricity price for dollars. Trading a 60 W incandescent for a 9 W LED running 4 hours a day saves about 74 kWh per bulb per year — around $11 at 15¢ per kWh.
How long does it take an LED bulb to pay for itself?
Divide the up-front cost of the LEDs by the monthly electricity saving. Because a modern LED costs a few dollars and removes roughly 85% of the bulb's power draw, most household swaps pay back within months. Fixtures that run many hours a day pay back fastest; a closet bulb used ten minutes a day may never justify a premium bulb.
Should I replace working incandescent bulbs or wait for them to burn out?
For anything on more than an hour or two a day, replacing early usually wins — the wasted electricity costs more than the unused life left in the old bulb. Set the hours slider to your real usage and look at the payback figure. Under a year, do it now; over five years, wait for the burn-out.
Do LED bulbs really last 25,000 hours?
That is the rated life printed on most boxes, measured to the point where light output falls to 70% of new rather than to outright failure. Heat is what actually kills them, so LEDs crammed into enclosed fixtures or recessed cans age faster. Both lifespans are editable here — enter 15,000 hours if your fixtures run hot.
How is the CO₂ figure calculated?
Kilowatt-hours saved × an emissions factor. The 0.39 kg CO₂/kWh default is close to the average across the United States grid and is offered as an average, not a measurement of your utility. Regions running on hydro or nuclear can be below 0.1; coal-heavy grids can pass 0.7. Edit the field if your provider publishes its number.
Does this account for the replacement bulbs I no longer buy?
Yes. Over the period you choose, the calculator counts how often each incandescent would burn out and charges those replacements, then does the same for LEDs. The donut splits total savings into an electricity share and a replacement-bulb share, and the net figure subtracts the LEDs you buy on day one.
What about brightness and light colour?
Match lumens, not watts. A 60 W incandescent puts out roughly 800 lumens, 75 W about 1,100, and 100 W about 1,600 — the LED box lists the same figure. Colour temperature is separate: 2700K reads as warm household light, 4000K as neutral, 5000K as daylight. Savings do not depend on which you pick.