How much can LEDs really save?

An LED uses roughly 80 to 90 percent less energy than an incandescent bulb for the same brightness. Replacing a 60 W incandescent with an 8 W LED saves about 52 W per bulb, which adds up quickly across many bulbs used several hours a day.

How is the payback calculated?

Payback divides the total cost of the LED bulbs by the annual bill saving they deliver. Because LEDs are cheap and the saving is large, payback is often well under a year for bulbs used several hours daily, then the saving is pure benefit for years.

Do LEDs last longer too?

Yes. LEDs typically last 15,000 to 50,000 hours versus around 1,000 for incandescent and 8,000 for CFL. That means far fewer replacements, an extra saving this calculator does not include, so real lifetime value is higher than the payback shown.

What old-bulb wattage should I use?

Use the actual wattage printed on the bulb. As a guide, common incandescent bulbs are 40, 60, or 100 W, halogens are 35 to 50 W, and CFLs are 11 to 20 W. The bigger the gap to the LED, the larger your saving.

Does brightness stay the same?

It should — match LEDs by lumens, not watts. A 60 W incandescent produces about 800 lumens, which an 8 to 10 W LED matches. Choosing by lumens ensures you keep the same light output while cutting the energy used.

LED Lighting Savings Calculator

This calculator quantifies the saving from swapping old bulbs for LEDs. You enter the number of bulbs, the old and new wattages, daily usage and your tariff, and it returns the annual energy and money saved, the CO2e avoided, and how quickly the LED bulbs pay for themselves.

How it works

Energy use is wattage times hours, so the saving is the wattage difference run over a year, converted to kWh and then to money and carbon:

watts_saved = (old_W − led_W) × bulbs
kWh_saved   = watts_saved / 1000 × hours_per_day × 365
bill_saving = kWh_saved × tariff_per_kWh
co2_saved   = kWh_saved × grid_factor (≈0.21 kgCO2e/kWh)
payback_yrs = (led_cost × bulbs) / bill_saving

Because LEDs draw a fraction of the power of the bulbs they replace, the watts saved per bulb is large and the saving scales directly with how many hours the lights are on.

Tips and example

Replacing ten 60 W incandescent bulbs with 9 W LEDs, used 4 hours a day at 0.25 per kWh, saves about 745 kWh and 186 a year while avoiding around 156 kg of CO2. At a few units per LED the bulbs pay for themselves in well under a year. Always match replacements by lumens rather than watts so brightness stays the same, and prioritise the bulbs that are on the longest each day.