LED vs Incandescent: The Full Cost Guide

The headline numbers

At the defaults, ten 9-watt LEDs use 98.55 kWh a year and cost $16.75 of electricity plus $1.31 of replacement bulbs, for $18.06 in total. Ten 60-watt incandescents use 657 kWh and cost $111.69 of electricity plus $10.95 of replacements, for $122.64 in total. The saving is $104.58 a year, and over ten years it is $1,045.80. Two facts drive almost all of it: the LED uses about one-seventh of the wattage for the same light, and it lasts about twenty-five times longer — 25,000 hours against 1,000. Everything else in this guide is detail around those two facts.

Why the wattage gap is so large

An incandescent bulb makes light by heating a filament until it glows, and most of the electricity leaves as heat rather than light. An LED makes light directly from a semiconductor, so far more of each watt becomes visible light. That is why a 9-watt LED matches a 60-watt incandescent at roughly 800 lumens, the standard brightness for an everyday room bulb. The practical rule is to shop by lumens, not watts: 800 lumens is the 60-watt replacement, 1,100 lumens replaces a 75-watt bulb, and 1,600 lumens replaces a 100-watt bulb. If you match lumens, the energy saving follows automatically; if you buy brighter LEDs than the bulbs they replace, you give some of it back.

The replacement treadmill

The second cost is quieter and easy to miss. At 3 hours a day, each bulb burns 1,095 hours a year. An incandescent rated for 1,000 hours therefore dies in under a year, so ten sockets need 10.95 replacements a year at $1.00 each — $10.95 a year, every year, plus the ladder trips and the dead-bulb drawer. An LED rated for 25,000 hours lasts over 22 years at the same usage, so ten sockets need just 0.438 replacements a year — $1.31 a year. The LED's higher shelf price, $3.00 against $1.00, is repaid in about ten weeks from the $104.58 annual saving, and after that the household is ahead by roughly $8.72 a month for as long as the LEDs live.

When the numbers move

The defaults are a modest house; real houses move the figures in predictable directions. With just 5 bulbs, LEDs cost $9.04 a year and incandescents $61.33, a $52.29 saving — even a renter who swaps one room still wins. With lights burning 6 hours a day, as kitchen and living-room lights do, LEDs cost $36.14 and incandescents $245.28, a $209.14 saving: swap the longest-burning lights first and the payback is fastest there. Where electricity costs $0.30 per kWh, LEDs cost $30.88 and incandescents $208.05, a $177.17 saving, because expensive power punishes the wasteful bulb hardest. And against 100-watt incandescents — keeping the 9-watt LED for a clean comparison — incandescent energy alone reaches 1,095 kWh costing $186.15, the incandescent total reaches $197.10, and the saving reaches $179.04 a year. (A true 100-watt-equivalent LED uses about 14 watts, which would still save nearly as much.)

When incandescents still make sense

The honest exceptions are narrow. Oven lights are the clearest: LED electronics cannot survive oven heat, so the appliance bulb stays incandescent or halogen by necessity. Some very old dimmers flicker or buzz with certain LEDs, though most modern dimmable LEDs have solved this — if a dimmer misbehaves, try a different LED brand before giving up. Enclosed fixtures can shorten LED life by trapping heat, so buy LEDs rated for enclosed fixtures where the fitting is sealed. And in a rarely used closet or attic, where a bulb burns a few hours a year, the saving is pennies and either bulb is fine. For ordinary room, porch, kitchen, and bathroom lighting, none of these exceptions change the verdict.

How to calculate your own house

Count the bulbs you actually use, not the sockets in the house — spare rooms and storage do not count. Estimate hours honestly: kitchen and living areas run 4 to 6 hours a day, bedrooms 1 to 2, bathrooms under an hour. Read your electricity rate from a recent bill, dividing the supply-plus-delivery total by kilowatt-hours used if the bill does not state a single rate. Then open the LED vs Incandescent Calculator, enter your count, hours, rate, wattages, prices, and lifespans, and read the annual totals: if the saving is over $50 a year, buy the LEDs on the next shopping trip and start with the longest-burning rooms. Keep the old working incandescents as spares for the oven and the attic, and recycle the dead ones rather than binning them where your area offers bulb recycling.