Using energy-saving lightbulbs

Lighting can account for up to 20% of a typical electricity bill in the UK, according to the Energy Saving Trust. One way to reduce lighting’s impact on your energy usage is to make the switch from traditional incandescent lighting to energy-saving bulbs instead. Read on to discover why and how.
Share this guide
Man changing energy-saving bulbs

In this guide:

  • How do energy saving light bulbs work?

  • What are the benefits of energy-saving light bulbs?

  • Types of low energy bulbs

  • How to choose the best energy-saving light bulbs 

  • How to get free energy-saving light bulbs

  • Money-saving lighting tips

How do energy-saving light bulbs work?

The key difference between traditional light bulbs and energy saving light bulbs is of course the way they produce light. Traditional ‘incandescent’ light bulbs work by heating a wire filament until it glows. This type of bulb is incredibly inefficient – 90% of the energy used to power them is ‘lost’ to heat, with a mere 10% converted into light.

In the 1950s, halogen light bulbs were invented as a more energy efficient and longer-lasting alternative. These improvements were down to the halogen gas content and make halogen bulbs around 30% more efficient than incandescent ones. Halogen bulbs started being phased out in 2016.

Modern energy-saving bulbs use one of two methods to produce light:

  • Compact fluorescent lamp

This was the first mass-produced low-energy lightbulb. Look closely at the bulb and you’ll see glass tubes inside. These are filled with mercury vapour and an electronic ballast to channel the electricity when you switch on the lights. When the electricity flows through, the mercury vapour emits light. The light is emitted in the ultraviolet range, stimulating a phosphorus coating that produces the bright light that we see. 

  • LED (Light-Emitting Diode bulb)

These pass an electric current through a silicon diode component, moving electrons to create light-emitting particles.

Low energy bulbs are designed to fit all standard light fittings, including bayonet and Edison screws. This makes them compatible with the lamps and other fixtures you already have around your home.

What is the equivalent wattage of an energy-saving light bulb?

Energy-saving light bulbs use significantly less electricity, measured in watts, than the incandescent bulbs they’re designed to replace. As you can see, LED bulbs offer even better savings that CFL ones, which results in major savings in energy, particularly over a bulb’s lifespan:

Updated 21 December 2020
Bulb typeLow brightnessMedium brightnessHigh brightness
Incandescent 40-60 watts 60-75 watts 75-100 watts
CFL 12-15 watts 15-18 watts 18-23 watts
LED 4-5 watts 6-8 watts 9-13 watts

Energy-saving light bulbs – lumen value

Traditionally, an incandescent bulb’s wattage was used to measure its brightness, but because energy-saving bulbs produce the same amount of light at a lower wattage, a different measurement is required to measure their brightness. This is known as the lumen output. At the bottom end of the scale, a low-power bulb (40 watts equivalent) produces 450 lumens, while a high-power bulb (100 watts equivalent) produces around 1,600 lumens.

Another way to measure a light bulb’s efficiency is by the number of lumens per watt it produces, with higher numbers indicating greater efficiency:

Updated 29 April 2021
Lumens per watt 15 256072
Percentage more efficient than incandescentN/A 28% 75% 83%

Source: HomeElectrical

Low energy light bulbs are also measured using a colour index. Soft or warm white bulbs cast a yellowish glow similar to traditional bulbs and are ideal for home lighting. Those marked as cool or pure white are brighter and clearer, ideal for workspaces or kitchens. Look at the Colour Rendering Index (CRI) on the bulb’s packaging to see its colour rating. 

What are the benefits of energy-saving light bulbs?

The major benefit is that energy-saving bulbs will reduce your electric consumption considerably, leading to cheaper electricity bills and reducing your house’s carbon footprint. It’s estimated that each bulb can save around 2,000 times its weight in carbon emissions during its lifespan.

Can energy-saving bulbs save me money?

Yes, over the longer term. Energy-saving bulbs are more expensive to buy than traditional incandescent bulbs, which makes some people hesitant to purchase them. However, when looking at the overall lifespan of the bulb, you’ll save money.

According to the Department of Energy and Climate Change, if a typical UK household replaced all its old-fashioned bulbs with energy-savings bulbs, and halogen bulbs with LED spotlights, it would save around £60 per year.

How long do energy saving bulbs last for?

Not only do energy-saving bulbs save you money on your electricity bills – using up to five times less energy in the process – they also last longer. Not only will you be spending more money on your monthly electricity bill with a less-efficient bulb, but you’ll also need to replace it more often. For example, incandescent light bulbs have a rated life of just 1,000 hours – around 1.4 years – while CFLs last for up to 14 years (10,000 hours) and LEDs up to 34 years (25,000 hours) – a vast improvement.

Energy-saving bulbs are becoming increasingly popular, and as demand has expanded, the costs have come down accordingly. You can now find energy-saving bulbs for under £1.50. 

Types of low energy bulbs

There are two main types of energy efficient light bulbs:

Compact fluorescent lamps (CFL)

Until recently, most energy-saving bulbs were CFLs. These are the types that contain argon gas and mercury vapour. Their main drawback is that it can take a few seconds for the bulb to reach maximum brightness, creating a brief warm-up period. The good news is that the effect is far less noticeable in modern bulbs, compared to earlier iterations that could take up to a minute to reach full brightness. A secondary drawback is that they contain mercury, which makes them harder to dispose of – make sure you properly recycle any used CFLs.

Light emitting diode (LED)

LED bulbs were invented decades ago, but it’s only in recent years that they’ve become a common, affordable option. These pass an electric current through a silicon diode component, moving electrons to create light-emitting particles, and use less than half the energy of CFL bulbs, with instant-on brightness to boot.

Are halogen bulbs energy efficient?

Yes and no. Although halogen bulbs are more energy efficient than incandescent bulbs, energy consumption is often greater. This is because people tend to use more of them in a room, since they’re designed to fit into ceiling recesses or open mounts. You’ll often see halogen bulbs used in spotlight ceiling bars, down-lighters, and decorative lighting fixtures.

Although a single halogen bulb might be 40 watts, if you position a row of lights along your ceiling the overall wattage might be higher than when using one or two incandescent bulbs. 

Halogen bulbs are also inefficient because they produce a lot of heat. To produce light, a current of electricity is passed through a thin tungsten filament. The tungsten heats up as it provides resistance to the electricity, eventually emitting a warm light. This process produces more heat than with other bulbs, which requires more energy.

The good news is that many halogen bulbs can be replaced with more energy-efficient LED alternatives.

Are fluorescent tube lights energy efficient?

It’s a common misconception that fluorescent tubes use significantly more electricity compared to other forms of lighting. They can be an efficient option, popular for lighting areas like kitchens, lofts, and garages. 

One thing to note is that like any other bulb, they have a limited lifespan. After several years, common signs that the tube has come to the end of its lifespan includes flickering. However, fluorescent bulbs come with replacement starter cartridges (look for a removable cylindrical object at one end of the light fitting) – it may be that this requires replacing rather than the light itself.

How to choose the best energy-saving light bulbs 

You’ll find CFLs and LEDs available in a wide range of powers, shapes, and mounts to suit most lighting fixtures in your home. Mounts for low energy bulbs include bayonet (BC and B22), small bayonet (SBC and B15), standard Edison screw (ES and E27) and small Edison screw (SES and E14). There are also GU-10 mounts to replace kitchen halogen bulbs, but these can’t be used to replace the low voltage halogen lights used in recessed ceilings.

When it comes to shapes there’s even more variety, whether you fancy a spiral, pear shape or golf ball. Typically, bulbs are either covered or uncovered. Covered shapes like candles and pears are slightly stronger, protecting the fluorescent tube behind an additional layer of glass. The downside of this is that it can slightly reduce energy efficiency because the light must penetrate an additional layer. 

How to get free energy-saving light bulbs

Sadly, free energy-saving light bulbs aren’t widely available unless occasionally part of a one-off, time-limited promotion through a retailer. That’s the bad news, the good news is that prices are falling all the time, and light bulbs are no longer a disposable item that need replacing every year or so. CFL bulbs will last up to 14 years, and LEDs will last even longer – up to 34 years. The trick to getting cheaper energy efficient bulbs is to buy in bulk from reputable online and DIY stores like Screwfix.

Money-saving lighting tips 

No matter which type of bulb you use, there are additional ways to save money on your electricity bills. A good way to start is by comparing energy deals to ensure you’re on the best possible tariff. Beyond this, you can save energy (and money) at home with the following tips. 

  • Turn off lights whenever you leave the room. 

  • Use daylight whenever possible. It’s the most energy efficient lighting out there. 

  • Dial down the wattage. Overly bright rooms can feel sterile and office-like, while bulbs with lower watts can create a more cosy, atmospheric effect. They also save energy at the same time. Dimmer switches can also reduce the amount of energy a light uses. 

  • Consider your fixtures. A common mistake is replacing a single incandescent bulb with multiple low-wattage bulbs in multiple fixtures. If you’re using more lights, you’ll consume more power, despite the low wattage. 

  • Install motion detectors outdoors or smart lighting systems that automatically turn off according to a timer or sensor. This will save you energy when not needed. 

  • Clean your light bulbs regularly. Like any other household surface, bulbs can attract dust which can obscure the light.

  • Install low energy bulbs with the correct light output. Use the table above to choose the correct wattage LED or CFL bulb.

Last updated: 21 December 2020