LED Savings Calculator

How much you save by swapping old bulbs for LEDs, and how many months it takes to get the cost back.

Saving a year

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Saving a year—

Saving a month—

You get your money back in—

Electricity saved—

Cut in consumption—

Cost of the bulbs—

CO₂ avoided a year—

How this was worked out

The formula

saving = (old wattage − LED wattage) ÷ 1,000 × hours × price per kWh

Where it comes from

An LED gives the same light as an incandescent bulb on about 87 % less power: 8 watts against 60. Since the bill is paid by the kilowatt hour, that difference turns straight into money, and the longer the bulb is on, the sooner it shows.

How to work it out by hand

Subtract the LED's wattage from the old bulb's
Divide by a thousand to get kilowatts
Multiply by the hours of use a year and by the number of bulbs
Multiply by the price of a kilowatt hour

What is worth knowing

What to look at when buying is not the watts but the lumens, which is the light it actually gives: around 800 lumens matches the old 60 W bulb. And colour temperature changes the feel of a room completely: 2700 K is warm light, like an incandescent; 4000 K is neutral, for kitchens and bathrooms; above 5000 K the light is cold and unpleasant in living rooms and bedrooms.

Frequently asked questions

How much do you save switching to LEDs?

Swapping ten 60 W bulbs for 8 W LEDs on four hours a day saves around 114 a year.

How long do they take to pay for themselves?

Usually less than a year. With heavy use, a few months.

Which LED matches a 60 W bulb?

One of about 800 lumens, which normally draws between 7 and 9 watts.

Which colour temperature should I pick?

2700 K for living rooms and bedrooms, 4000 K for kitchens and bathrooms. Above 5000 K the light feels cold.