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All light bulbs in the UK are required to meet new energy efficiency standards. 

Energy saving bulbs come in a range of shapes, sizes and brightness. There are energy saving bulbs for every type of fitting, including dimmable. 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

Halogens are more efficient than old-style incandescent bulbs, however they are still high usege and are being phased out. Homes will still have existing halogen bulbs, and so it’s worth being aware that rooms lit by halogens (typically kitchens) usually have lots of them which increases the overall cost.


Compact fluorescent light bulbs are 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 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 achieve full brightness instantly, are available in almost all fittings and styles, are dimmable, and come in a wide range of colours, including hues close to traditional incandescent bulbs. LEDs are more expensive (although you can find them cheaper than the average £6 listed in our table, especially if you buy multi-packs) but their extremely low energy consumption means that they are likely to save between £45 and £75 over 10 years. In some fittings, they use a tenth of the electricity of the equivalent halogen bulbs. 

How do they compare?

Average purchase price£6.00£3.50£2.00
Typical lifetime*30 years10 years2 years
Yearly purchase costs (over 30 years)20p35p£1.00
Running cost per year**£0.84£1.55£4.92

* Of 1,000 hrs per year | ** 14.05p/kW | Tables: Energy Saving Trust

Smart bulbs 

These are LED bulbs which connect to the Wifi or Bluetooth system within the home. They allow you to turn your lights on and off via a remote, your phone, your tablet or your voice controlled home assistance system. They also enable you to set timers for your lighting to come on and off. There is not much evidence that having this control saves you money, but they can be very useful for people with mobility issues or for those who have concerns around home security.

Picking the right bulb 

The choice available when buying new lightbulbs can be dizzying. Here’s a few steps to help you buy the right bulb:
1. Know the fitting and bulb shape
Bulbs come in a wide variety of fittings, such as screws, bayonets or pins. The easiest option is to take the old bulb shopping with you, and compare it to the options available. You can also compare when shopping online, but be aware some fittings look the same but come in different sizes.

The shape of the bulb will affect how the light is distributed. Bulbs with a more traditional or candle shape offer an evenly distributed, diffuse light. Spotlights provide a more focussed light. You do not have to replace bulbs with one of the same shape; any bulb with the same fitting will work.

2. How bright do you want it? 
Traditionally we refer to brightness of bulbs by how many watts it uses, and we tend to know how bright a 60W or 100W bulb is. However, low energy lightbulbs will use less power to deliver the same brightness. Packaging will often list ‘60W equivalent’, but is not always a reliable comparison. For complete accuracy, look at the ‘lumens’, which is a measurement of how much light is produced. See our table for a comparison of Watts to lumens.

3. What colour? 
One advantage of LED technology is the ability to produce a range of colours, which are measured in Kelvin (K). It is possible to buy LED’s that range from very warm (1,800K), with a strong orange look, to cool daylight (7000k), which has a stark bluey appearance. Warm white (2700k) is the most popular option and gives a similar light to an incandescent bulb. Cool white (4000K) provides quite a bright light which is often popular in kitchens and bathrooms, giving a modern look.

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).

LumensOld-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? Do you need lights left on in hallways or landings? It is particularly important to use low-energy bulbs in places where you really do need to have the light on for long periods.

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

Old-style bulb

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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