Why LEDs save so much
Incandescent bulbs turn about 90% of their energy into heat. LED bulbs give the same light, measured in lumens, with about 80 to 85% less electricity:
| Light output | Incandescent | Halogen | LED |
|---|---|---|---|
| 450 lumens | 40 W | 29 W | 5 to 6 W |
| 800 lumens | 60 W | 43 W | 8 to 10 W |
| 1,100 lumens | 75 W | 53 W | 11 to 13 W |
| 1,600 lumens | 100 W | 72 W | 14 to 17 W |
How the savings are calculated
- kWh saved per year = bulbs × (old watts − LED watts) × hours per day × 365 ÷ 1,000
- Money saved = kWh saved × price per kWh
- Payback = cost of the new bulbs ÷ monthly savings
Worked example
You replace 10 incandescent bulbs of 60 W with 9 W LEDs, used 3 hours a day, with electricity at $0.17 per kWh and LEDs at $3 each.
- Energy saved: 10 × (60 − 9) × 3 × 365 ÷ 1,000 = 558 kWh per year.
- Money saved: 558 × 0.17 = $95 per year.
- Payback: $30 ÷ ($95 ÷ 12) = 3.8 months.
- Over 10 years, after buying the bulbs: about $919.
- CO₂ avoided at the US grid average of about 0.37 kg per kWh: 207 kg per year.
Lifespan
LED bulbs are rated for 15,000 to 25,000 hours, against about 1,000 hours for incandescent bulbs. At 3 hours a day, one LED can last more than 13 years, replacing a dozen or more old bulbs, which adds to the savings.
Choosing LED bulbs
- Compare lumens, not watts. The Lighting Facts label on the box lists brightness, yearly energy cost and color.
- Color temperature: 2,700 K gives a warm white like old bulbs; 4,000 to 5,000 K is cooler and brighter, good for kitchens and workspaces.
- Dimmers: buy bulbs marked dimmable, and check that your dimmer is LED-compatible to avoid flicker.
- ENERGY STAR bulbs are tested for brightness, color and lifespan.
- Start with the bulbs you use the most, such as the kitchen, living room and outdoor lights; savings are proportional to hours of use.
Most general-service incandescent bulbs can no longer be sold in the US since 2023, but many homes still have them in use or in a drawer.