LED Upgrade Payback Calculator

LEDs have gotten cheap. A quality A19 LED bulb now costs $1-3. That makes the payback period surprisingly short — often under a month for bulbs running several hours a day.

The math

Annual energy savings (kWh) = (old_watts - led_watts) / 1000 x hours_per_day x 365

Annual savings ($) = kWh_savings x electricity_rate

Payback (months) = led_cost / (annual_savings / 12)

Where the savings are real

A 60 W incandescent swapped for a 9 W LED saves 51 watts. At 5 hours a day that is 93 kWh a year, worth about $14.90 at the current US average of $0.16/kWh. A $2 bulb pays for itself in six weeks and then keeps paying.

Halogen swaps are smaller per bulb but there are usually more of them. A 50 W halogen replaced by a 6 W LED saves 44 watts, and a house with 20 recessed cans running 4 hours a day saves about $205 a year.

CFL to LED is the closest call. CFLs already cut consumption sharply, so the electricity gap is modest and the payback is mostly about lifespan and not waiting for the light to warm up.

Lifespan, and the arithmetic people get wrong

At 5 hours a day a 25,000-hour LED runs for 13.7 years. Over those same 25,000 hours you would have bought roughly 25 incandescents at 1,000 hours each, or 3 CFLs at 8,000. That bulb-replacement cost is real money on top of the electricity, and it is worth far more than money in a fixture that needs a ladder.

The savings concentrate in the bulbs that run longest. Do the kitchen, the living room and the porch light first; the closet bulb can stay incandescent until it dies of old age.