Light Bulb Savings Calculator
Calculate how much money you save by switching from incandescent or CFL bulbs to LED, based on wattage, usage, and electricity rate.
Switching from incandescent bulbs to LED is one of the simplest and most impactful ways to reduce electricity costs. This calculator quantifies exactly how much you save and how long until the investment pays back.
Key formulas:
Energy Use (kWh) = Wattage × Hours Used ÷ 1,000 Annual Energy Cost = kWh per Year × Electricity Rate ($/kWh) Annual Savings = Incandescent Annual Cost − LED Annual Cost Payback Period (months) = (LED Bulb Cost − Incandescent Cost) ÷ (Monthly Savings)
What each variable means:
- Wattage — power drawn by the bulb (W). LED equivalent wattage is far lower than incandescent.
- Hours Used — average daily or annual hours of operation.
- Electricity Rate — U.S. average is ~$0.13/kWh, but ranges from $0.08 (Louisiana) to $0.29 (Hawaii).
Wattage equivalents:
| Incandescent | LED Equivalent | Light Output |
|---|---|---|
| 40W | 6–8W | 450 lumens |
| 60W | 8–10W | 800 lumens |
| 75W | 11–13W | 1,100 lumens |
| 100W | 15–18W | 1,600 lumens |
Worked example: Replace a 60W incandescent with a 9W LED. Used 4 hours/day. Electricity at $0.13/kWh. LED costs $4; incandescent $0.75.
Incandescent annual kWh = 60W × 4h × 365 ÷ 1,000 = 87.6 kWh → $11.39/year LED annual kWh = 9W × 4h × 365 ÷ 1,000 = 13.14 kWh → $1.71/year Annual Savings = $11.39 − $1.71 = $9.68 Payback = ($4 − $0.75) ÷ ($9.68/12) = $3.25 ÷ $0.81 = 4 months
LEDs also last 15,000–25,000 hours versus 1,000 hours for incandescent — about 25× longer.