LED Savings Calculator
Compare the running cost of incandescent or halogen bulbs with LED replacements and see the annual saving.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
LED bulbs turn roughly 80-90% of the electricity they draw into light, where an incandescent bulb wastes about 90% as heat. Swapping a 60 W bulb for a 9 W LED with the same brightness saves over 50 kWh a year per bulb. If the replacement does not reduce energy use or the entered electricity rate is zero, the payback period is not available. Set the lamp count to one for a single replacement. Watts saved refer to all selected lamps; energy and cost savings are annual, and payback is in months.
Worked example
calculated with the default values below
Number of bulbs 10 · Old bulb wattage 60 W · LED wattage 9 W · Hours used per day 4 h · Electricity rate 0.17 $/kWh · Price per LED bulb 3 $ Energy saved per year 745 kWh · Money saved per year 126.58 $ · Payback period (months) 2.8 mo · Wattage saved 510.0 W
General background references
Disclaimer
These calculators provide planning estimates only. Building codes, wiring regulations and safety requirements differ by country and change over time, and nothing here replaces a licensed professional or a permit. For structural, electrical or gas work, follow local code and have the installation inspected.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
E = n × max(W_old − W_led, 0) ÷ 1000 × h × 365; save = E × r; payback = n × p ÷ save × 12
- n
- number of bulbs
- W_old
- old bulb power (W)
- W_led
- LED power (W)
- h
- daily use (hours)
- r
- electricity rate per kWh
- p
- price per LED bulb
Annual energy saved (kWh); payback is in months and is undefined when modeled savings are zero.
Frequently asked questions
How quickly do the LED bulbs pay for themselves here?
Each swapped bulb saves the difference in wattage, 60 minus 9 equals 51 W. Across 10 bulbs at 4 hours daily the tool saves about 745 kWh a year, worth roughly 127 at 0.17 per kWh. Since the ten LEDs cost 30, the payback is under three months, about 2.8, after which the savings are pure. Usage hours drive the result more than bulb count.