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Energy-saving light bulbs use up to 90% less electricity than the old bulbs but produce the same amount of light. And they last over 10 times longer.

Since 2011, all light bulbs in the EU have been required to meet new energy efficiency standards. Because of the phasing out of inefficient old-style bulbs and replacing them with energy efficient alternatives, a typical UK household now uses nearly a third less electricity to light their home than it did in the late 1990s.

Since 2016 only light bulbs with an energy rating of B or better have been available to buy. A typical old-style (incandescent) bulb would have an energy rating of E.

Like the old-style bulbs, energy saving ones come in a range of shapes, sizes and brightness. There are energy saving bulbs for every type of fitting and even dimmable low-energy bulbs have been developed. What’s more, you can now choose to have a variety of colours of light to suit your taste..

There have been three generations of low-energy light bulbs: halogen bulbs, compact fluorescent light bulbs (CFLs) and light emitting diodes(LEDs). Each produce more light for every unit of electricity than their predecessor and each generation lasts for longer too.

Halogen bulbs

These bulbs provided a very similar light as incandescent bulbs. Halogens are more efficient than old-style incandescent bulbs, however rooms lit by halogens usually have lots of fittings  (for example kitchens) which increases the overall cost of lighting. Halogens are now considered a high-energy using bulb and their sale has been phased out since 2016.


Compact fluorescent light bulbs or CFLs are now very widespread and often what people think of as a low energy bulb. They often look like tubes shaped into a helix or a series of loops, though it is now possible to get CFLs in a range of traditional bulb shapes. Early examples were criticised for poor light quality and for the length of time it took to get up to full brightness. Nowadays CFLs are much improved but have increasingly become a second best option to LEDs.


Light emitting diodes, usually referred to as LEDs, are the most efficient bulbs available. They’ve been around for years as little lights on TVs and as bicycle lights. They achieve full brightness instantly, can be dimmed and come in a wide range of colours, including hues close to traditional incandescent bulbs. LEDs are more expensive to buy but their extremely low energy consumption means that they are likely to save between £45 and £75 over an average lifespan (10 years). In some fittings, they use a tenth of the electricity of the equivalent halogen bulbs. LEDs are now available in almost all fittings and styles.

How do they compare?

 Halogen bulbsCFL bulbsLED bulbs
Rough cost per bulbn/a£6£6
Typical energy saved*20-30%75%85%
Average lifespan (hours)2,00010,00020,000
Time to reach full brightnessInstant30-120 secsInstant
Typical running cost per year£9.86£3.08£1.85

*compared to an equivalent old-style incandescent bulb

Watts and lumens

Light bulbs have traditionally been rated in watts. The wattage tells you how much electricity a light bulb will use and enables you to work out how much it will cost to run. The amount of light given off is measured in lumens. These days, when you buy a light bulb you will see a figure for lumens as well as the wattage rating on the packaging.

The table below shows the wattage you’d need to produce the same brightness with different types of bulbs. You can use it as a guide to converting your old bulbs to more energy efficient equivalents. For instance, you could replace a 100 watt old-style bulb with a 20 watt LED bulb and get the same amount of light (using much less electricity).

Lumens (brightness)Old-style bulbHalogen bulbCFL bulbLED bulb

Turn them off!

Finally, if you’re worried about your electricity bill, one of the best things you can do is keep an eye on your household’s use of lighting. Are lights switched off when they’re not needed or are they being left on in unoccupied rooms? What about passageways and landings? Do you really need those lights on all the time? It is particularly important to use low-energy bulbs in places where you really do need to have the light on for long periods of time.

Image: LED bulb, Tom Raftery | reproduced under a Creative Commons license

Frequently asked questions

Don't energy saving light bulbs take a long time to light up to full brightness?

Many years ago this would have been the case. However modern low energy light bulbs get up to full brightness very quickly. LED light bulbs are also becoming more popular. These are extremely efficient and light up instantly.

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Are low energy light bulbs as bright as the equivalent tungsten light bulbs?

Low energy bulbs come in a range of power-ratings. It will tell you on the box what the rating of the equivalent old-fashioned bulb would be for low energy bulb you are buying.

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We can advise you about saving energy, or help you understand what grants and support you're eligible for:

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Are there low energy light bulbs for all types of fitting?

Gone are the days when an energy saving light bulb had to stick out of the top of your lampshade. Low energy light bulbs are now available to fit the majority of fittings and come in a variety of shapes and sizes.

Need more help?

We can advise you about saving energy, or help you understand what grants and support you're eligible for:

Contact us Or freephone: 0800 082 2234

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This information is available as a freely downloadable PDF from this page.

For more domestic energy advice, view all our advice pages.

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