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Light Bulb Replacement Savings Calculator

Work out light bulb replacement savings instantly with clear inputs, formula shown and shareable results.

About Light Bulb Replacement Savings Calculator

Replacing a 60 W incandescent with an 8 W LED saves 52 W for every hour it burns. Across fifteen bulbs at four hours a day that is 1,139 kWh a year — well over three hundred pounds — with a payback measured in weeks rather than years.

Formula

Lighting saving

saved kWh = (old W - new W) x bulbs x hours x 365 / 1000; payback = bulb cost / annual saving

Worked example

With the default values below, Light Bulb Replacement Savings Calculator returns Annual saving of $318.86. Change any input above and every figure here is recalculated in your browser.

Inputs used

Bulbs to replace
15 bulbs
Old bulb wattage
60 W
LED wattage
8 W
Hours used per day
4 h/day

Results

Annual saving
$318.86
Annual energy saved
1,138.80 kWh
Payback on 3 per bulb
1.69 months
Ten-year saving
$3,143.64

Step by step

  1. 1Values used
  2. 2Lighting saving
  3. 3Annual saving= 318.86
  4. 4Annual energy saved= 1,138.80 kWh
  5. 5Payback on 3 per bulb= 1.69 months
  6. 6Ten-year saving= 3,143.64

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Which bulbs should I replace first?

The ones on longest: kitchen, living room and hallway. A bulb used ten minutes a day saves almost nothing however inefficient it is.

Do LEDs really last 25,000 hours?

The LED itself often does, but the driver electronics frequently fail sooner, especially in enclosed fittings where heat builds up.

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