Efficiency · 6 min read
LED vs incandescent bulbs: the real yearly cost difference
A single 60W incandescent run 6 hours a day at the US-average rate costs $21.60 a year. The equivalent 9W LED costs $3.24. Across a typical house of 40-60 bulbs that delta is $700-1,100 a year in electricity alone.
The single-bulb math
A standard 60W incandescent bulb running 6 hours a day pulls 360 watt-hours, or 0.36 kWh a day. Over 365 days that's 131.4 kWh. At the US-average residential rate of 16.5¢/kWh, the bulb costs $21.68 a year to run.
The 9W LED that produces the same ~800-lumen output uses 19.7 kWh a year and costs $3.25. The savings per bulb, per year: $18.43. That's for one bulb running six hours. Scale the hours or the rate and the number moves proportionally.
Key insight
The 6.67× rule.
What a whole-house swap is actually worth
An average US house has 40-60 light bulbs. Not all of them run six hours a day: kitchen and living room fixtures do, bedroom and closet bulbs run 1-2 hours, decorative and outdoor fixtures vary by season. A reasonable blended average is 3 hours a day across all sockets.
Take a 50-bulb house, all still running 60W incandescent, at 3 hours a day average. That's 9 kWh a day, or 3,285 kWh a year, or $542 a year at 16.5¢/kWh. Swap every bulb to a 9W LED and the same house uses 493 kWh a year and costs $81. Annual savings: $461.
In higher-rate states the gap is steeper. The same swap in California at 31¢/kWh saves $865 a year. In Hawaii at 41¢/kWh it saves $1,144.
The "but LEDs cost more" objection
A quality 9W LED bulb runs $3-6 at retail. A 60W incandescent runs about $1. On sticker price alone the incandescent looks cheaper. The math changes fast when you look at total cost of ownership.
An incandescent is rated for ~1,000 hours. A 9W LED is rated for ~25,000 hours. Over the LED's life you'd replace 25 incandescents. Purchase cost comparison:
- 1 LED: $5
- 25 incandescents: $25
Before you count a single kWh, the LED is already $20 cheaper. Add the electricity delta over 25,000 hours at 16.5¢/kWh: incandescent uses 1,500 kWh ($248), LED uses 225 kWh ($37). Lifetime cost difference: $231 per socket. Across 50 sockets: $11,550 over the LED's life.
The payback if you're swapping today
If all your current bulbs still work and you're deciding whether to swap early: a $5 LED replacing an incandescent running 3 hours a day pays for itself in electricity savings in about 5-6 months. After that, everything is net positive. A kitchen fixture running 8 hours a day pays back in 2-3 months. A closet bulb running 15 minutes a day takes 5-6 years and probably isn't worth a pre-emptive swap.
The short version: replace high-use fixtures first (kitchen, living room, porch, hallway), replace low-use bulbs as they burn out.
When LEDs aren't the obvious winner
Dimmer compatibility.Older triac dimmers were designed for resistive incandescent loads and don't play well with every LED. Symptoms: flicker, buzzing, or a narrow dim range. The fix is either a dimmer-compatible LED (the packaging will say so) or a newer LED-rated dimmer switch ($15-25).
Enclosed or recessed fixtures.LEDs don't like heat. A non-enclosed-rated LED in a sealed fixture can fail early. Check the package for "enclosed fixture rated" before buying for a recessed can.
Very-low-use fixtures. A closet bulb that runs 10 minutes a day uses about 0.18 kWh a year as an incandescent. The annual cost delta is 12 cents. Not worth a pre-emptive swap; replace when it burns out.
Oven, appliance, and heat-resistant applications. Incandescent is still standard. LEDs fail in high-heat environments.
CFLs and halogens in the middle
Incandescent and LED aren't the only two options, but the middle ground has mostly closed. A 14W CFL replaces a 60W incandescent and costs about $5.06 a year to run at 6 hours a day at US-average rates. That's $1.81 more a year than the equivalent LED, which doesn't sound like much until you multiply by 50 sockets. CFLs also contain a small amount of mercury and have shorter rated lives than LEDs (~8,000 hours vs 25,000).
Halogens are incandescents with a small efficiency bump. A 43W halogen produces the same light as a 60W incandescent, saving about 28% on electricity. That's a quarter of the LED's savings at a comparable purchase price. There's no argument for halogen over LED on running cost.
What brightness actually matches
Watts are a power measurement. Lumens are the actual light output. When shopping LED replacements, match lumens, not watts:
- 40W incandescent ≈ 450 lumens → 4-6W LED
- 60W incandescent ≈ 800 lumens → 8-10W LED
- 75W incandescent ≈ 1,100 lumens → 11-13W LED
- 100W incandescent ≈ 1,600 lumens → 14-17W LED
Color temperature also matters: 2,700K-3,000K LEDs look like classic incandescent. 4,000K-5,000K looks like office lighting. Picking the wrong color temperature is the #1 reason people return LEDs and declare the swap a failure.
Check it against your own bill
Look at your current annual kWh (the utility portal usually shows a 12-month rollup). Assume lighting is 8-12% of a typical residential bill. If your lighting load is 300 kWh a month on incandescent, dropping to LED takes it to roughly 45 kWh. At your local rate that's a specific dollar number you can verify on the next bill. See reading-your-electric-bill if you need a refresher on where the kWh total lives on the page.