Work out what your home uses, what it costs and what it needs

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How much do you save by switching to LED bulbs?

Pick the bulbs you have, how many and how many hours a day you use them. We’ll tell you what you save a year, how long the LEDs take to pay for themselves and how long they last.

Check your bill: the total divided by the kWh.

To see how long they take to pay for themselves.

It’s on the box. 15,000 h was the minimum ENERGY STAR required of the LEDs it certified.

🔒 The maths runs on your own phone or computer. We don’t store or send your data.

What you save

You save per year
—
In money, per year
—
They pay off in
—
ChangekWh a year lessThe LED lasts

Not counting what you save on replacement bulbs.

Next steps

How it’s worked out

  1. The kWh you stop using = (bulb watts − LED watts) × how many × hours a day × 365 ÷ 1,000.
  2. The money = those kWh × what you pay per kWh.
  3. How long they take to pay off = what all the LEDs cost ÷ the money you save per year.
  4. How long the LED lasts = the hours on its box ÷ (hours a day × 365). ENERGY STAR, the U.S. government’s efficiency program, required at least 15,000 hours of the LEDs it certified (and 10,000 of compact fluorescents).

For incandescent bulbs, the calculator suggests the replacement LED by lumens (the light it gives), using the ENERGY STAR table: a 60 W bulb gives 800 lumens. For the LED watts it uses the most an LED rated class F on the European label would draw, which means at least 85 lumens per watt: 800 ÷ 85 = 9.4 W. If yours is more efficient, it uses less and you save more. For halogens, compact fluorescents and tubes, enter the watts of the LED you’ll fit.

With what it loads when you open it: 4 incandescent 60 W bulbs on 5 hours a day become 9.4 W LEDs: (60 − 9.4) × 4 × 5 × 365 ÷ 1,000 = 369.4 kWh a year. And one 100 W bulb, 3 hours a day, becomes an 18.8 W LED: (100 − 18.8) × 3 × 365 ÷ 1,000 = 88.9 kWh. In total, 458 kWh a year, 84% less on those bulbs. At 0.20 per kWh that’s 91.66 a year; if each LED costs 3, the 5 cost 15 and pay for themselves in 15 ÷ 91.66 × 12 = 2 months. On 5 hours a day, a 15,000-hour LED lasts 15,000 ÷ (5 × 365) = 8.2 years.

We explain how to choose the right LED (lumens, light colour and label) in how much LEDs save and which to choose.

Sources