How To Tell If A Light Bulb Is Energy Efficient

low energy light and incandesant light side by side

We’ll tell you what you need to know about low energy lighting

We all know we should be using less energy and that changing lights to low energy lighting is an important part of the process.

However, it’s not always easy to know what type of lighting we have in the first place.

In this article I’ll explain:

  • Which of these types are not low energy and may need replacing.
  • A simple method to identify which lights are low energy and which aren’t.
  • How low energy lights can reduce your energy bills and CO2 emissions.
  • Is it better to change inefficient lights bulbs now or wait until they go.


The four most common types of lighting found in the home


Uk homes typically can have any combination of these 4 lighting types.

Incandescent bulbs

These are the traditional light bulbs that have been used for decades in UK homes. They work by heating a filament inside the bulb to produce light.

However, incandescent bulbs are not energy-efficient and have largely been phased out in favour of more energy-efficient options.

Incandescent light bulb
Halogen light bulb

Halogen bulbs

These are similar to incandescent bulbs but use a halogen gas to increase their efficiency and lifespan.

Halogen bulbs are still used in some UK homes, but they are not as energy-efficient as LED bulbs.

CFLs (Compact Fluorescent Lamps)

These are energy-efficient bulbs that use a gas to produce light.

They are more efficient than incandescent and halogen bulbs, but they take a moment to warm up to full brightness.

Compact florescent light bulb
LED Light

LEDs (Light Emitting Diodes)

These are the most energy-efficient type of bulb available in the UK.

They use a semiconductor to produce light and are more durable and longer-lasting than other types of bulbs.

LEDs are becoming increasingly popular in UK homes as the technology has improved and prices have come down.

How do I know if my light bulb is low energy?

To determine if your light bulb is low energy, you can look for the energy efficiency rating label on the packaging.

The new energy rating label shows a rating from A (most efficient) to E (least efficient) and gives information on the bulb’s energy and power consumption amount, brightness, and expected lifespan.

You can also check the wattage of the bulb, as low energy bulbs usually have lower wattages than traditional incandescent bulbs.

For example, a 60-watt incandescent bulb can be replaced with a 9-watt LED bulb that uses significantly less energy.

Another way to identify low energy bulbs is to look for the lumens, which measure the brightness of the bulb.

Low energy bulbs can produce the same amount of light (or lumens) as more traditional bulb bulbs while using less energy.

For example, a 60-watt incandescent bulb produces around 800 lumens, while a 9-watt LED bulb can produce the same amount of light.

In addition, many low energy bulbs in the UK will be labeled with the “Energy Saving Trust Recommended” logo, which signifies that the product has been independently tested and approved as energy-efficient.

Still not sure?

Then here is a simple technique to identify whether a light in your home is a low energy light or not.

Anyone can do it, you don’t need any technical knowledge, you don’t need any special tools.

It’s a simple technique that I often use in my daily job as a Domestic Energy Assessor.

I said you don’t need any tools, but the only thing you will need is a thermostat. Luckily, we all have a built in thermostat called our skin. In the example we’re simply going to use the back of our hand. Here’s how.

Incandescent lights and halogen lights are not low energy lights. They are inefficient because they give off a lot of heat in the process of producing the light.

  1. Turn on the light you wish to test and leave it on for around 30 seconds.
  2. Next, slowly raise the back of your hand towards the light.
  3. When your hand is about 50mm (2 inches) away from the bulb, one of two things will happen.

You will either feel a lot of heat coming from the bulb and as you move your hand marginally closely to the bulb you will feel the heat getting hotter and your in built thermostat in your skin will sense that if you go any closer you’re going to get burnt and to stop there. This bulb is not a low energy light.

On the other hand if you feel no heat coming from the light, move your hand closer to the light and if you feel no heat, slowly move it closer still.

You will get to the point where you can safely touch the bulb with the palm of your hand because it isn’t hot. If that happens, then you have an LED light.

If you feel a small amount of heat coming from the bulb, not hot enough to burn but warm enough to feel it, then you probably have a compact fluorescent light (cfl) bulb. These bulbs are classed as low energy, but they are not as efficient as LEDs.

What makes a light bulb more energy efficient

A bulb is typically considered a low energy light if it has a luminous efficacy of at least 60 lm/W.

  • Lumens (lm) is the amount of light emitted.
  • Watts (W) is the amount of energy used.

The more lumens produced by the watts of energy used, the more efficient the bulb.

For example, LED bulbs can have a luminous efficacy of up to 200 lm/W, while CFL bulbs typically have a luminous efficacy of around 50-70 lm/W.

Incandescent bulbs, on the other hand, have a luminous efficacy of only around 10-17 lm/W.

·         LED and CFL light would be classed as energy efficient.

·         Incandescent and halogen lights would be classed as in-efficient.

However, it’s not all about brightness, as in the real world different activities require different amounts of lights, such as to be able to perform a task or to set a desired mood.

What is the difference between LED and low energy bulbs

LED (Light Emitting Diode) bulbs and low energy bulbs (such as CFLs or Compact Fluorescent Lamps) are both energy-efficient lighting options that use less electricity than traditional incandescent bulbs.

However, there are some differences between these two types of energy saving light bulbs.

One major difference is the technology used to produce light. LED bulbs use a semiconductor to generate light, while low energy bulbs use an electric current to excite a gas or vapor, which then produces light.

This means that LED bulbs are generally more durable and longer-lasting than low energy bulbs, as they do not contain fragile filaments or gases that can degrade over time.

Another difference is the level of light energy and efficiency. LED bulbs are the most energy-efficient lighting option available, as they can convert up to 80% of the electricity they consume into visible light.

Other low energy bulbs, on the other hand, are less energy-efficient, typically converting around 50-75% of their energy into light.

In terms of brightness and the colour temperature, LED bulbs can provide a range of colours and brightness levels, while low energy bulbs may take a moment to reach full brightness and can sometimes have a yellowish tint.

Overall, both LED bulbs and low energy bulbs are energy-efficient lighting options that can help reduce electricity bills and lower carbon emissions.

However, LED bulbs are generally more durable, longer-lasting, and more energy-efficient than low energy bulbs.

How do the energy rating of lights work

In the UK, the new energy rating for lights is based on a system called the “EU energy label”.

This label is designed to help consumers understand how energy efficient a light bulb is, and to make it easier to compare different products.

The energy label ranks light bulbs on a scale from A to G, with A being the most energy efficient and G being the least efficient.

The label also includes information about the bulb’s brightness, measured in lumens, and its estimated lifespan, measured in hours.

The label applies to all types of light bulbs, including incandescent bulbs, halogen bulbs, and LEDs.

However, since September 2021, halogen and old incandescent bulbs are no longer permitted for sale in the UK as part of efforts to reduce carbon emissions.

Although an E rating may sound poor, it is still classed as energy-efficient. For example under the new 2021 building regulations, which is extremely demanding, the average efficiency across all lights must be at least 80 lm/W.

The new energy rating system is part of a wider effort to reduce energy consumption and carbon emissions in the UK.

By choosing more energy efficient light bulbs, consumers can save money on their energy bills and help to protect the environment.

Although an E rating may sound poor, under the new rating scheme, it is still classed as energy-efficient.

Even the best domestic light you could purchase is rated an E rating. Therefore if your lights are rated F or E then this is considered a good rating.

The current rating gives scope for newer more efficient technologies to be rated as and when they become available.

New 2021 Lighting energy rating label

Energy Rating

Is it better to change inefficient lights bulbs now or wait until they go?

It is generally more cost-effective to replace incandescent light bulbs with low-energy alternatives, such as LED lights or CFL bulbs, even if the incandescent bulb has not yet failed. This is because low-energy bulbs use significantly less electricity than incandescent bulbs, which can result in lower energy bills over time.

In addition, low-energy bulbs tend to last much longer than incandescent bulbs, so you may save money on replacement costs in the long run.

While low-energy bulbs may have a higher upfront cost, this cost is typically offset by the energy savings and longer lifespan.

Overall, it is recommended to switch from halogen light bulbs to low-energy bulbs as soon as possible to start saving money and reducing energy consumption.

How much does low energy lighting improve the EPC rating?

In the domestic home, low energy lighting only raises the EPC rating a small amount.

So for example to go from no low energy lights to 100% low energy lights only raises the EPC rating by 2 points.

However, this is a simple DIY job that any homeowner can do and by default a home owner should aim to boost there EPC with this simple improvement. 


Rickie Dickson
Written by Rickie Dickson

Rickie Dickson is an experienced and qualified domestic and non domestic energy assessor. He helps homeowners and businesses in all matters relating to energy efficiency, from meeting building regulations compliance to improving a property’s energy rating score.