How LED vs incandescent cost is worked out
An LED and an incandescent bulb are priced on the same thing: the electricity they burn plus the bulbs they use up. The total hours are the hours a day times 365 times the years: 3 × 365 × 10 = 10,950 hours. The energy is the watts times the hours divided by 1,000, in kilowatt-hours, and the energy cost is the kilowatt-hours times the price a kWh. The bulbs are the hours divided by the life, rounded up: the LED lasts 15,000 hours and the incandescent lasts 1,000 hours. The total is the energy cost plus the bulbs times the bulb price, and the winner is the smaller total.
At the defaults — 3 hours a day, $0.16 a kWh, LED 9 W, incandescent 60 W, LED bulb $3.00, incandescent bulb $1.00, horizon 10 years — the LED uses 9 × 10,950 ÷ 1,000 = 98.55 kWh, which costs 98.55 × $0.16 = $15.77, and needs ceil(10,950 ÷ 15,000) = 1 bulb, which is $3.00, for a total of $18.77. The incandescent uses 60 × 10,950 ÷ 1,000 = 657.00 kWh, which costs 657.00 × $0.16 = $105.12, and needs ceil(10,950 ÷ 1,000) = 11 bulbs, which is $11.00, for a total of $116.12. The LED wins by $116.12 − $18.77 = $97.35. A year costs $1.88 for the LED against $11.61 for the incandescent, and the energy alone is $1.58 a year against $10.51.
| Case | LED total | Incandescent total | Winner |
|---|
| Default (3 h/day, 10 years) | $18.77 | $116.12 | LED by $97.35 |
| 1 h/day | $8.26 | $39.04 | LED by $30.78 |
| 6 h/day | $37.54 | $232.24 | LED by $194.70 |
| $0.30/kWh | $32.57 | $208.10 | LED by $175.54 |
| $0.08/kWh | $10.88 | $63.56 | LED by $52.68 |
| LED 12 W | $24.02 | $116.12 | LED by $92.10 |
| Incandescent 40 W | $18.77 | $81.08 | LED by $62.31 |
| 5-year horizon | $10.88 | $58.56 | LED by $47.68 |
| 25-year horizon | $45.42 | $290.80 | LED by $245.38 |
| Flip: 0.05 h/day | $3.26 | $2.75 | Incandescent by $0.51 |
The worked example, line by line
Setup: 3 hours a day, $0.16 a kWh, LED 9 W, incandescent 60 W, LED bulb $3.00, incandescent bulb $1.00, horizon 10 years.
Line 1 — the hours. 3 × 365 × 10 = 10,950 hours.
Line 2 — the LED energy. 9 × 10,950 ÷ 1,000 = 98.55 kWh, and 98.55 × $0.16 = $15.77.
Line 3 — the LED bulbs. ceil(10,950 ÷ 15,000) = 1 bulb, which is $3.00.
Line 4 — the LED total. $15.77 + $3.00 = $18.77.
Line 5 — the incandescent energy. 60 × 10,950 ÷ 1,000 = 657.00 kWh, and 657.00 × $0.16 = $105.12.
Line 6 — the incandescent bulbs. ceil(10,950 ÷ 1,000) = 11 bulbs, which is $11.00.
Line 7 — the incandescent total. $105.12 + $11.00 = $116.12.
Line 8 — the winner. $116.12 − $18.77 = $97.35 to the LED. A year costs $1.88 for the LED against $11.61 for the incandescent.
Every branch, checked
1 hour a day: the hours are 1 × 365 × 10 = 3,650 hours, the LED energy is 9 × 3,650 ÷ 1,000 = 32.85 kWh, which costs $5.26, and 1 bulb is $3.00, for a total of $8.26. The incandescent energy is 60 × 3,650 ÷ 1,000 = 219.00 kWh, which costs $35.04, and 4 bulbs are $4.00, for a total of $39.04. The LED wins by $30.78. Less use shrinks the gap, because the saving is in the energy, and less use means less energy to save on.
6 hours a day: the hours are 6 × 365 × 10 = 21,900 hours, the LED energy is 197.10 kWh, which costs $31.54, and 2 bulbs are $6.00, for a total of $37.54. The incandescent energy is 1,314.00 kWh, which costs $210.24, and 22 bulbs are $22.00, for a total of $232.24. The LED wins by $194.70. More use grows the gap, because every extra hour is 51 watts the LED does not burn.
$0.30 a kWh: the LED energy costs 98.55 × $0.30 = $29.57, for a total of $32.57, and the incandescent energy costs 657.00 × $0.30 = $197.10, for a total of $208.10. The LED wins by $175.54. Dear electricity is the LED’s best friend: the saving is the wattage gap times the price, so dearer power means a bigger saving.
$0.08 a kWh: the LED energy costs 98.55 × $0.08 = $7.88, for a total of $10.88, and the incandescent energy costs 657.00 × $0.08 = $52.56, for a total of $63.56. The LED wins by $52.68. Cheap electricity shrinks the saving, but the LED still wins, because the bulb itself is only $3.00 against $11.00 of incandescent bulbs.
LED 12 W: the LED energy is 12 × 10,950 ÷ 1,000 = 131.40 kWh, which costs $21.02, for a total of $24.02, while the incandescent stays $116.12. The LED wins by $92.10. A brighter LED costs more to run, but 12 watts is still a fifth of 60, so the saving barely moves.
Incandescent 40 W: the incandescent energy is 40 × 10,950 ÷ 1,000 = 438.00 kWh, which costs $70.08, for a total of $81.08, while the LED stays $18.77. The LED wins by $62.31. A dimmer incandescent narrows the gap, because the wattage gap is what the LED saves on.
5-year horizon: the hours are 3 × 365 × 5 = 5,475 hours, the LED energy is 49.28 kWh, which costs $7.88, and 1 bulb is $3.00, for a total of $10.88. The incandescent energy is 328.50 kWh, which costs $52.56, and 6 bulbs are $6.00, for a total of $58.56. The LED wins by $47.68. A shorter horizon halves the saving, because the saving accrues by the hour.
25-year horizon: the hours are 3 × 365 × 25 = 27,375 hours, the LED energy is 246.38 kWh, which costs $39.42, and 2 bulbs are $6.00, for a total of $45.42. The incandescent energy is 1,642.50 kWh, which costs $262.80, and 28 bulbs are $28.00, for a total of $290.80. The LED wins by $245.38. Over 25 years the LED needs 2 bulbs and the incandescent needs 28.
Flip — 0.05 hours a day (3 minutes a day): the hours are 0.05 × 365 × 10 = 182.50 hours, the LED energy is 1.64 kWh, which costs $0.26, and 1 bulb is $3.00, for a total of $3.26. The incandescent energy is 10.95 kWh, which costs $1.75, and 1 bulb is $1.00, for a total of $2.75. The incandescent wins by $0.51. In a closet that is on for 3 minutes a day, the bulb price beats the energy saving, because neither bulb ever burns out in 10 years.
Reverse — the break-evens: the LED stops winning when the LED bulb costs $100.35, because the LED energy is $15.77 and the incandescent total is $116.12, so $116.12 − $15.77 = $100.35. The LED starts winning at 0.07 hours a day (4.03 minutes a day): below that the $2.00 dearer bulb costs more than the energy it saves. An incandescent bulb would need to draw 4.43 W to tie the LED, which is below any real incandescent bulb, so the LED wins at any realistic wattage.
What the defaults assume
The model assumes the LED lasts 15,000 hours and the incandescent lasts 1,000 hours, which are the usual rated lives, and it assumes both bulbs give the same light, so the comparison is fair. It assumes the electricity price stays flat for the whole horizon, with no price rises, and it assumes the bulb is on for the same hours every day. It leaves out the cost of the fitting and the labour, which are the same for both sides, and it leaves out the heat an incandescent throws off, which warms a room in winter and fights the air conditioning in summer. Rounding convention: money is rounded to cents, energy to 2 decimals, and all figures are computed from unrounded values, rounded only for display.
Output · formula · meaning
| Output | Formula | What it means |
|---|
| Total hours | hours/day × 365 × years | 10,950.00 hours. |
| LED energy | LED watts × hours ÷ 1000 | 98.55 kWh, costing $15.77. |
| LED bulbs | ceil(hours ÷ 15,000) | 1 bulb, costing $3.00. |
| LED total | LED energy cost + LED bulbs | $18.77. |
| Incandescent energy | incandescent watts × hours ÷ 1000 | 657.00 kWh, costing $105.12. |
| Incandescent bulbs | ceil(hours ÷ 1,000) | 11 bulbs, costing $11.00. |
| Incandescent total | incandescent energy cost + incandescent bulbs | $116.12. |
| Winner | smaller total | LED wins by $97.35. |
| LED per year | LED total ÷ years | $1.88/yr. |
| Incandescent per year | incandescent total ÷ years | $11.61/yr. |
| LED energy per year | LED energy cost ÷ years | $1.58/yr. |
| Incandescent energy per year | incandescent energy cost ÷ years | $10.51/yr. |
| 1 h/day | same model, 1 h/day | LED $8.26 vs incandescent $39.04, LED wins by $30.78. |
| 6 h/day | same model, 6 h/day | LED $37.54 vs incandescent $232.24, LED wins by $194.70. |
| $0.30/kWh | same model, $0.30 | LED $32.57 vs incandescent $208.10, LED wins by $175.54. |
| $0.08/kWh | same model, $0.08 | LED $10.88 vs incandescent $63.56, LED wins by $52.68. |
| LED 12 W | same model, 12 W | LED $24.02 vs incandescent $116.12, LED wins by $92.10. |
| Incandescent 40 W | same model, 40 W | LED $18.77 vs incandescent $81.08, LED wins by $62.31. |
| 5-year horizon | same model, 5 years | LED $10.88 vs incandescent $58.56, LED wins by $47.68. |
| 25-year horizon | same model, 25 years | LED vs incandescent , . |
| Flip: 0.05 h/day | same model, 0.05 h/day | LED $3.26 vs incandescent $2.75, Incandescent wins by $0.51. |
| Reverse: max LED bulb price | incandescent total − LED energy | $100.35. |
| Reverse: minimum use | tie point, 1 bulb each | 0.07 h/day (4.03 min/day). |
| Reverse: break-even incandescent watts | (LED total − incandescent bulbs) × 1000 ÷ (hours × rate) | 4.43 W. |
Who uses this
- The homeowner swapping every bulb in the house: they learn one LED costs $18.77 over 10 years against $116.12 for the incandescent — so they know each swap saves $97.35, and they check the 6-hours-a-day room at $194.70 first.
- The renter with cheap electricity: they learn the LED still wins by $52.68 at $0.08 a kWh — so they know the swap pays even where power is cheap, and they check the $3.00 bulb against the $11.00 of incandescent bulbs.
- The homeowner with a closet light: they learn the incandescent wins by $0.51 at 3 minutes a day — so they know a closet bulb is the one place not to bother, and they check the 4.03-minutes-a-day line before they decide.
- The landlord pricing a whole building: they learn 25 years of one socket costs $45.42 for the LED against $290.80 for the incandescent — so they know the LED saves $245.38 a socket, and they check the 28 incandescent bulbs against the 2 LEDs.
Accuracy & limitations
The math is exact for the numbers you enter: the hours are the hours a day times 365 times the years, the energy is the watts times the hours divided by 1,000, the bulbs are the hours divided by the life rounded up, and the winner is the smaller total. What the model cannot do is read your electricity bill for you: check the price a kWh on the bill, because a $0.08 bill and a $0.30 bill give very different savings. It assumes the rated lives of 15,000 and 1,000 hours, a flat electricity price, and the same hours every day, and it leaves out the fitting, the labour and the heat an incandescent throws off. For the oven that heats the kitchen, see gas vs electric oven calculator; for the TV, see streaming vs cable calculator.
Cite this calculatorBright Side Kit. “LED vs Incandescent Bulb: 10-Year Cost Calculator 2026.” brightoolbox.com, 2026. Method: Total hours = hours/day × 365 × years; energy kWh = watts × hours ÷ 1000; energy cost = kWh × $/kWh; bulbs = ceil(hours ÷ life), LED life 15,000 h, incandescent life 1,000 h; total = energy cost + bulbs × bulb price; winner = lower total. Defaults: 3 h/day, $0.16/kWh, LED 9 W, incandescent 60 W, LED bulb $3.00, incandescent bulb $1.00, 10 yr → 10,950 h; LED 98.55 kWh, $15.77 energy, 1 bulb, $3.00 bulbs, total $18.77; incandescent 657.00 kWh, $105.12 energy, 11 bulbs, $11.00 bulbs, total $116.12; LED wins by $97.35; per year LED $1.88 vs incandescent $11.61; energy/year LED $1.58 vs incandescent $10.51; 1 h/day → LED $8.26 vs incandescent $39.04, LED by $30.78; 6 h/day → LED $37.54 vs incandescent $232.24, LED by $194.70; $0.30/kWh → LED $32.57 vs incandescent $208.10, LED by $175.54; $0.08/kWh → LED $10.88 vs incandescent $63.56, LED by $52.68; LED 12 W → LED $24.02 vs incandescent $116.12, LED by $92.10; incandescent 40 W → LED $18.77 vs incandescent $81.08, LED by $62.31; 5-yr horizon → LED $10.88 vs incandescent $58.56, LED by $47.68; 25-yr horizon → LED $45.42 vs incandescent $290.80, LED by $245.38; flip 0.05 h/day → LED $3.26 vs incandescent $2.75, incandescent by $0.51; reverses: max LED bulb price $100.35; minimum use 0.07 h/day (4.03 min/day); break-even incandescent wattage 4.43 W. Bright Side Kit. "LED vs Incandescent Bulb: 10-Year Cost Calculator 2026." https://brightoolbox.com/led-vs-incandescent-calculator/ Accessed October 25, 2026.
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