Incandescent bulbs turn most of the electricity they draw into heat. LEDs turn most of it into light. That single difference is why a lighting swap is still the cheapest, fastest energy upgrade available to most households — and the math is simple enough to check yourself.
The core difference in efficiency
A traditional 60-watt incandescent bulb produces roughly 800 lumens of light. A modern LED produces the same 800 lumens using about 8 to 10 watts. You are paying for roughly one sixth of the electricity for the same brightness.
Lumens measure light output; watts measure electricity drawn. When you shop, compare lumens for brightness and watts for running cost. A bulb labelled "60W equivalent" is telling you about lumens, not about what it actually consumes.
- Incandescent: ~800 lumens at 60W — roughly 13 lumens per watt
- Halogen: ~800 lumens at 43W — roughly 19 lumens per watt
- CFL: ~800 lumens at 14W — roughly 57 lumens per watt
- LED: ~800 lumens at 9W — roughly 89 lumens per watt
How to calculate the cost yourself
Annual kilowatt-hours = watts ÷ 1,000 × hours used per day × 365. Multiply that by your electricity rate in dollars per kWh — the number is printed on your utility bill — to get annual cost.
Example: one 60W incandescent running 3 hours a day is 60 ÷ 1000 × 3 × 365 = 65.7 kWh per year. At $0.17/kWh that is about $11.17. The 9W LED replacement uses 9.9 kWh, about $1.68. The difference is roughly $9.50 per bulb per year.
Scale that across a home. Twenty bulbs on the same usage pattern is around $190 a year of avoided electricity, before you count the replacement bulbs you no longer buy.
Lifespan and replacement cost
Incandescent bulbs are typically rated for 1,000 hours. LEDs are commonly rated 15,000 to 25,000 hours. At three hours per day, that is roughly one incandescent per year versus one LED every 14 to 22 years.
Rated life is a statistical median under test conditions. Enclosed fixtures, high ambient heat and poor-quality drivers all shorten real-world life, so treat the rating as a comparison tool rather than a promise.
Where LEDs are less obviously better
In a closet you open twice a week, the payback period stretches out for years, because savings scale with hours of use. Prioritise kitchens, living rooms, porches and any fixture that runs for hours each evening.
In cold climates, the waste heat from an incandescent does slightly offset heating during winter. In an air-conditioned home in summer, the opposite is true: you pay twice, once for the heat and again to remove it.
FAQ
- Do LEDs really save money if they cost more upfront?
- In fixtures used a few hours a day, yes. A bulb that saves roughly $9 a year in electricity typically pays back a $3 purchase price in under six months, then keeps saving for a decade or more.
- Are LED bulbs as bright as incandescent bulbs?
- Brightness is measured in lumens, not watts. Match the lumen rating — around 800 lumens replaces a standard 60W incandescent — and the perceived brightness will be the same.
- Why does LED light sometimes look different?
- Color temperature and color rendering vary. Choose 2700K for the warm look of an incandescent, and a CRI of 90 or higher where color accuracy matters, such as kitchens and bathrooms.
Keep reading
Free guide
10 Key Tips to Lower Your Electric Bill
A short, practical PDF you can work through in a weekend. No fluff, no hype — just the changes that move a real electric bill.
- The 3 changes that cut the most kWh first
- A room-by-room LED swap checklist
- How to read your bill and spot the expensive habits
- Where phantom loads hide — and how to measure them
