Category: Energy Efficiency

Since the manufacture of traditional incandescent light bulbs ceased in 2016 it has become far less common to see them in UK homes. The same is true of halogen light bulbs that which the UK government banned from sale in September 2021. The reason behind this is to reduce the 11% of domestic electricity consumption used for lighting.

Traditional lights bulbs only convert around 5-10% of the electricity they use into light (the rest is given off as heat). They also didn’t last long as the tungsten filament used to produce the light is prone to breaking. Low energy alternatives are Compact Florescent Lights (CFLs) and Light Emitting Diode (LED) lights.

CFL bulbs

This type of bulb is typically 75% more efficient than an incandescent or halogen light bulb and can last up to ten times longer. In the early days users would often complaints about the length of time they took to light up and about the dimness of the light they produced.

Although CFLs did get better they are also being phased out. The reason for this is because they contain small amounts of mercury. The RoHS (Restriction of the use of Hazardous Substances) initiative means that the production of CFL’s, and most fluorescent tubes (T5 and T8) will stop from February 2024. Although it is still legal to buy CFL bubs, it will get harder to find them as existing stocks dry up.

LED bubs

LED bulbs are typically 90% more efficient than an incandescent or halogen bulb and twice as efficient as a CFL bulb. LED bulbs also last significantly longer (estimated at around 25,000 hours) than halogen (estimated at around 2,000 hours) and CFL light bulbs (estimated at around 10,000 hours – roughly 10 years).

Despite this, not everyone liked using LED bulbs when they were first introduced for household lighting, due to the harshness of the light they produced. Much has changed since then, with a much wider choice of colour and brightness available. Indeed, one of the advantages now of LEDs over other types of bulb is the shear range of colours available, measured in Kelvin (k).

Colour

The Colour Rendering Index (CRI) of a bulb tells you how well a bulb will illuminate a chosen colour compared to sunlight measured on a scale of 0-100. The higher the number the more accurate the colour will be. A CRI of 80 or more is appropriate for most household tasks, although great colour rendering, with all colours easily distinguishable starts at a CRI of 90.

Further information on the box will tell you whether the bulb has been manufactured to produce a blue, white (often referred to as cool white or pure white) or a more relaxing yellow white (often referred to as warm white or soft white). In terms of Kelvin, you can expect to a very warm, orange light to have a rating of 1,800k and a stark, bluey light to have a rating of 7,000k. Nearest to the light given off by an incandescent bulb is a warm white, with a rating in the region of 2,700k.

Lumens

Historically, we bought lightbulbs based on watts (W).  However, this is a measure of the amount of electricity consumed rather than brightness (which is measured in lumens). A 100-watt bulb would be bought for a room we wanted well-lit and a 60- or 40-watt bulb for table lamps.

Today bulbs are sold based on the number of lumens they produce, although sometimes the box will also provide a guide to the number of watts the lumens equate to. The Energy Saving Trust provide a useful comparison table of watts and lumens on their website. A couple of examples from that table are 470 lumens being equivalent to 40-watts and 1,520 lumen being equivalent to 100-watts.

Energy Ratings for bulbs

Like other electrical goods light bulbs have to an A-G energy label of the box. With an A now being the most energy efficient bulb available (A+, A++ or A+++ ratings no longer exist) and G the worst, this label can help you choose the most efficient bulb which meets your lighting needs.

Smart bulbs

Most smart bulbs are LED, with the added advantage of being controllable remotely, via a phone or tablet (and sometimes voice commands as well). Depending on the manufacturer, these smart bulbs can be switched between cool and warm white (and for more expensive smart bulbs other colours too), be dimmed and, be programmed to automatically turn on and off. Some also have motion sensors.

If you want to go down the smart bulb route, it is best to do your research before you buy and stick to one bulb manufacturer. The reason for this is the variations in connectivity used by different manufacturers. Some (like the Philips smart bulb) need a smart hub; some have built in Wi-Fi (like LIFX smart bulbs) and others work over Bluetooth as well as (or instead of Wi-Fi). To control a bulb that uses only by Bluetooth you will need to be within a specific range – often no more than ten meters.

Bulb replacement

One of the biggest savings that can be made by any householder is replacing halogen spotlights for an LEDs in the rooms that are the most frequently used. This is not just because LED bulbs are more efficient (and you will not be able to buy halogen bulbs in future), but because of the number of spotlights usually linked together on one switch. If you are unlucky you will need to replace the transformers in the existing fitting to switch from a halogen to LED bulb. If you are not sure about this, it is best to consult with an electrician.

According to the Energy Saving Trust switching a 35-watt halogen bulb for an LED once can save you up to £4 per bulb per year (based on a 525-lumen bulb running for 521 hours per year). Multiply that by six and you have a saving of up to £28 a year, albeit less the initial investment of buying replacement bulbs.

The last bulbs to replace in your home are the ones which are used the least – for example, the bulb in the attic used for storage only, under the stairs or in a cupboard. The payback on replacing bulbs in spaces like these will be minimal. In most cases you are safe to wait until the bulb stops working.