LED Savings Calculator (switch old bulbs to LED)

Understanding the LED bulb savings calculator — concept and principle

This calculator works out how much money, electricity and replacement bulbs you save per year by switching old bulbs to LEDs, how long the LEDs take to pay for themselves and the net saving over five years.

Watts saved × hours: with the default inputs the result is $105.89 a year (payback 3.4 months).

How it is calculated

Hours per year = hours per day × 365.
Energy saved (kWh) = bulbs × (old W − LED W) × hours ÷ 1,000; money = kWh × price.
Replacement bulbs avoided = bulbs × hours per year ÷ old-bulb life; their cost = number × old-bulb price.
Total yearly saving = electricity saving + replacement saving.
Payback (months) = LED cost ÷ (yearly saving ÷ 12).
Net over 5 years = 5 × yearly saving − LED cost.

The principle

A bulb's energy use is its power times the hours it is on. Incandescent bulbs turn most of their energy into heat, while LEDs produce the same light with far fewer watts; the US Department of Energy says LEDs use up to 90% less energy. Incandescent bulbs also burn out after about 1,000 hours, while LEDs last many times longer, so you stop buying replacements too. The payback period compares the up-front cost with the monthly saving.

Worked example

Default inputs: 10 bulbs, 60 W old, 9 W LED, 3 h a day, $0.17/kWh, LED $3 each, old bulb life 1,000 h at $1.

Hours per year = 3 × 365 = 1,095.
Energy saved = 10 × 51 × 1,095 ÷ 1,000 = 558 kWh; money = 558.45 × 0.17 = $94.94.
Replacements avoided = 10 × 1,095 ÷ 1,000 = 10.9 bulbs = $10.95.
Total saving = $105.89 a year (old bulbs $111.69, LEDs $16.75; energy use cut 85%).
LED cost = $30.00; payback = 30 ÷ (105.89 ÷ 12) = 3.4 months; net over 5 years = 529.45 − 30 = $499.43.

Each point is the calculator re-run with only “Old bulb power (W)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Old bulb power (W)	Money saved per year
15	$22.12
30	$50.04
45	$77.96
60	$105.89
75	$133.81
90	$161.73
120	$217.58

How to read the result

Bulbs used for many hours a day pay back fastest; a bulb in a rarely used cupboard may never be worth replacing early. Pick LEDs by lumens, not watts: an 800 lm LED replaces a 60 W incandescent. Check colour temperature and whether the LED suits your dimmer.

Common mistakes

Comparing watts instead of lumens when choosing an LED.
Using a dimmer that is not compatible with the LED.
Overestimating hours of use.
Forgetting that LEDs in enclosed or very hot fittings may have shorter lives.

Keep in mind: Savings depend on your actual usage and prices. This is an estimate, not financial advice.

Frequently asked questions

How much do LED bulbs save per year?

Replacing ten 60 W bulbs used 3 hours a day with 9 W LEDs saves about $106 a year at $0.17/kWh, including replacements.

What LED replaces a 60 W bulb?

One rated at least 800 lumens.

How long do LED bulbs last?

Typically around 15,000 to 25,000 hours, many times longer than incandescent bulbs.

Sources: US Department of Energy, Energy Saver, "Lighting choices to save you money" · ENERGY STAR, "Light Bulb Purchasing Guide" (2020)

Checked 9 Nov 2026. U.S. Department of Energy, Energy Saver “Lighting choices to save you money” (LEDs use up to 90% less energy and last up to 25 times longer; incandescent life about 1,000 h, LED about 25,000 h); ENERGY STAR “Light Bulb Purchasing Guide” (2020) for watts-to-lumens equivalents.

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