Why LEDs use less energy
An incandescent bulb turns ~90% of its electricity into heat; an LED turns ~90% into light. The same brightness needs a 60 W incandescent but only a 9 W LED — an 85% energy cut. Over a bulb's life (LEDs last 15,000–25,000 hours vs 1,000 for incandescent), the savings dwarf the purchase price.
The math
Yearly cost per bulb: watts ÷ 1000 × hours/day × 365 × rate. The calculator compares old vs LED across all your bulbs, shows the yearly saving, and divides the LED purchase cost by the annual saving to get payback time (usually 2–8 months).
Example
10 × 60 W bulbs, 4 h/day, $0.16/kWh: incandescents cost $140/year; LEDs cost $21. That's $119 saved per year — and $25 of LEDs pays for itself in 2.5 months, then saves for a decade.
Beyond the bulbs
- Heat bonus: in summer, incandescents also make your AC work harder; LEDs remove that load.
- Replacement cost: incandescent bulbs die ~25× faster; LED replacements are a rounding error by comparison.
- Dimmable & colour: modern LEDs match warm light; check the box for dimmable compatibility.
- Smart bulbs add scheduling — but a plain LED already captures 95% of the saving.