LED Conversion Savings Calculator
Calculate the annual electricity cost savings and CO₂ reduction you'll achieve by swapping incandescent or CFL bulbs for LEDs. Use it to justify the upfront cost of an LED retrofit.
About this calculator
LED bulbs consume a fraction of the power of incandescent equivalents, and those savings compound across many bulbs and operating hours. The annual savings formula is: Annual Savings = (currentWattage × numBulbs × dailyHours × 365 × electricityRate / 1000) × (1 − ledEfficiency). The first term computes the annual electricity cost of running your existing bulbs: wattage is converted to kWh (÷ 1000), multiplied by hours per year (dailyHours × 365), number of bulbs, and rate. The factor (1 − ledEfficiency) captures the fractional reduction in wattage when switching to LED. For example, if an LED uses 15 % of the wattage of an incandescent, ledEfficiency = 0.15 and (1 − 0.15) = 0.85, meaning you save 85 % of the original cost. A typical LED replacement uses 75–85 % less energy than an equivalent incandescent.
How to use
You have 10 incandescent bulbs rated at 60 W each, used 5 hours/day, with electricity at $0.13/kWh. The LED replacements consume 9 W each, so ledEfficiency = 9/60 = 0.15. Step 1 — current annual cost: (60 × 10 × 5 × 365 × 0.13) / 1000 = $142.35/year. Step 2 — savings factor: 1 − 0.15 = 0.85. Step 3 — annual savings: $142.35 × 0.85 = $121.00/year. With LED bulbs costing roughly $3 each ($30 total), payback is approximately 30 / 121 ≈ 3 months.
Frequently asked questions
How do I calculate the LED efficiency ratio for my specific bulbs?
The LED efficiency ratio (ledEfficiency) is simply the LED bulb's wattage divided by the wattage of the bulb it replaces: ledEfficiency = LED watts / original watts. A 9 W LED replacing a 60 W incandescent gives a ratio of 0.15, meaning the LED uses only 15 % of the power. You can find both wattages on the bulb packaging—look for 'Replaces X W incandescent' on LED packaging, or check the spec sheet. If you're replacing CFLs (which are already more efficient), the ratio will be higher—typically 0.6–0.7—so savings are smaller but still meaningful.
What is the average annual savings per bulb when switching from incandescent to LED?
At the U.S. average electricity rate of about $0.16/kWh and typical usage of 3 hours per day, replacing a single 60 W incandescent with a 9 W LED saves approximately 51 W × 3 h × 365 days / 1000 ≈ 55.8 kWh/year, worth about $8.93/year per bulb. For 10 bulbs that's nearly $90/year. The actual figure depends heavily on your electricity rate and how many hours the lights run—households with high rates or heavily used fixtures see proportionally larger savings. Over a typical LED lifespan of 15,000–25,000 hours, the savings easily dwarf the purchase price several times over.
How long does it take to recoup the cost of LED bulb replacements?
Payback period = upfront cost of LEDs / annual electricity savings. At roughly $2–5 per quality LED bulb and annual savings of $8–12 per bulb (at average U.S. rates and 3–5 hours/day usage), payback ranges from a few weeks to about six months per bulb. Fixtures used many hours per day—porch lights, kitchen lights, office spaces—pay back within weeks, while rarely used closet lights may take a year or two. Because LEDs last 15–25 years versus 1–2 years for incandescents, you also avoid frequent bulb replacement costs, which further shortens the true payback when those avoided costs are included.