LED Lighting

Everything You Need To Know

It wasn't long ago that we were all replacing our traditional incandescent lighting with compact fluorescent lights - those little tubes that took a while to light up a room, and cast a slightly different coloured light than we were used to. The new revolution is LED lighting, which brings a number of benefits.

Energy Savings

LEDs use less energy than either traditional incandescent bulbs or compact fluorescent (energy saving) bulbs. The difference is startling: to produce the same amount of light, an LED will use approximately 10% of the amount of energy as a halogen bulb, less than 20% of the energy of an incandescent bulb, or around 50% of the energy of a compact fluorescent bulb.


To put this in financial terms: in a largish, modern house using mainly halogen bulbs (for example a house with recessed downlighters), an annual lighting electricity bill of £750 can be reduced to £75 by using LED bulbs, saving £675 each year.


10% of the energy use also means 10% of the greenhouse gas emissions during use - so LED bulbs help the planet too.

Longer Life

Traditional incandescent bulbs rely on hot metal wires (filaments) to work; as they are turned off and on, the filament expands and contracts, and eventually breaks.


Compact fluorescent bulbs (normal energy-saving bulbs) are more reliable, but still don't last forever. In normal use, you'll need to change them every few years. Some cheaper bulbs also lose performance after a while, so a bulb that was nice and bright when you installed it becomes dull and uninspiring.


LED bulbs last longer than either incandescent or compact fluorescent bulbs. In fact, many are now rated for 20,000-30,000 hours of use. To put this into context, an LED bulb lit for 10 hours a day, every day, would last for over 8 years of continuous use. More commonly, lights are lit for 3-4 hours a day on average, meaning that the LED bulb you buy today may last for over 30 years.


When choosing LED bulbs, do check how long the manufacturer or reseller guarantees the bulb for. You'll probably not find any company who will literally guarantee the bulb for 30 years, but many suppliers provide 2 or 3-year guarantees.


Be aware that cheap LED bulbs are available freely on eBay, often shipped directly from China. We've experimented with these and have found they are not built to last; one batch we tested lasted for only 3 months of occasional use! With LED bulbs, cheap is often not the same as good.

What Fitting to Choose

If you wish to fit LED bulbs, you have two choices: replace your existing bulbs, or replace the fitting.


Replacing existing bulbs is cost-effective and easy. LED replacement bulbs are available for most common fittings including bayonet, Edison Screw (ES) in both sizes, and GU10 and MR16 fittings often used for halogen spotlight bulbs in ceiling-mounted downlighters.


There are, however, a number of considerations you need to be aware of.


Physical Bulb Size


LED bulbs sometimes have a different physical size than traditional bulbs. In fittings with limited space for the bulb, check in advance whether the LED bulb you are looking at will actually fit. Note that, as LED bulbs produce very little heat, it is sometimes possible to use a larger bulb without risk of overheating parts of the light fitting, such as paper shades.


MR16 (halogen) replacement bulbs come in 50mm, 35mm and other sizes, depending on the diameter of the bulb they're replacing.




Individual LEDs are very directional - they produce light which covers a small area. An LED bulb generally consists of several individual LEDs. If they all shine in the same direction, the bulb will produce directional light. If they are clustered to point in different directions, the bulb will produce a more even light. Using a directional bulb will produce an uneven light and may cast more shadows, which can sometimes be a problem with spotlight bulbs in particular.


Some designs also include diffusers or reflectors, which help spread the directional light around.




Some LED bulbs are dimmable, but these are typically more expensive. If you have a dimmer switch, make sure you use dimmable bulbs, unless you wish to replace the dimmer with a normal on-off switch.


Even dimmable LED bulbs are not compatible with all dimmer switches. Results vary quite a bit between different bulbs and different dimmers, but invariably you will need a "trailing edge" dimmer switch. Unless you know you already have one of these, budget to buy a new dimmer - if you get the wrong dimmer, you could blow your brand new LED bulbs (we've seen this done!)


Replacing Compact Halogen (Downlighter / Spotlight) Bulbs


This is a little more complex, but the overall effect of replacing halogen bulbs can be huge, in terms of cost-savings and the quality of light produced.


Halogen bulbs come in two common fittings: GU10 bulbs have two mushroom-shaped pins and twist in to the socket to fit, whereas MR16 bulbs have two prongs and push in to fit. GU10 bulbs are generally 240V, whereas MR16 bulbs are nearly always 12V, used widely in bathrooms and kitchens. Before choosing an LED bulb, you'll need to take out one of your halogen bulbs and check carefully whether it is GU10 or MR16, and 240V or 12V.


12V halogen bulbs will operate off a transformer (either one per bulb, or one per group of bulbs). Some transformers are fussy about the power rating of the bulb they supply, so for example a 50W transformer may not operate properly with a 20W halogen bulb. However, in this case, you may still be able to use a 5W LED bulb (which is roughly equivalent to a 50W halogen bulb), but you may not be able to use a 3W LED bulb (which is roughly equivalent to a 30W halogen bulb). Sounds confusing? Yes, it doesn't make a lot of sense on the face of it - if in doubt, contact us for advice.


Halogen bulbs get very hot in use, and fittings are often designed to keep the bulb away from things the heat may damage. However, if you replace halogen bulbs with LED bulbs, which do not get anywhere near as hot, this may no longer be a consideration. For example, it may be that by replacing your halogen bulbs with LED bulbs, you can replace the loft insulation over the top of the ceiling fittings, improving your house insulation. Always check with us before setting fire to your house!


Replacing Fittings


In some cases, for example if fittings are old or tatty, you may want to consider replacing light fittings with ones that are specifically designed for use with LED bulbs. A good example is outside security lights, which often use horribly inefficient 300W or 500W incandescent bulbs; the heat from the bulb will often degrade the fitting, or damage its waterproof seals, and replacing it with a £20-30 LED-based security light will save a lot of money and hassle.

Colour Temperature and Light Colour

In the early days of LEDs, only specific colours of light were available - 30 years ago, red and green was about as good as it got.


As technology has progressed, a much wider range of colours is now available. However, be aware that the colour of light from an LED bulb may be different than that of an incandescent or compact fluorescent bulb it replaces.


LED bulbs are often available in cool, warm and daylight variants. The difference is in the colour temperature: a specific measurement of the peak colour, and range of colours, that the bulb produces. Note that this isn't in any way a measure of how hot the bulb actually gets in use!


Cool LED bulbs produce a light with a subtle but distinct blue-white tint. This may be ideal in a modern bathroom or utility room, but in a room with warm colours, the light can sometimes be stark and unpleasant. A cool white bulb may have a colour temperature of 4000K.


Daylight LED bulbs produce a light that appears bright but cool. As with cool bulbs, in a warm-coloured room they can produce a distinctive colour cast, but this may be useful in a commercial property such as a shop floor, or in an artist's studio, for example. A daylight bulb may have a colour temperature of 6000K.


Warm LED bulbs are most suitable for indoor use, producing a white light with a subtle warm yellowish tint. Warm LED bulbs are often used as a direct replacement for incandescent or halogen bulbs; they are less yellow than halogen bulbs, and often produce a clearer, more crisp light. A typical colour temperature would be 3000K.


Given all the choice, you may be wondering what to go for. Why not try out several bulbs before you commit a lot of money on a colour you may not be happy with? We offer a try-before-you-buy service which gives you a chance to audition different bulbs in your house before you spend your money.

Power (Wattage) Rating and Brightness

Power is a measure of how much energy a bulb consumes, and is measured in watts, where one watt is one joule of energy per second.


A 60W bulb will convert 60 joules of energy per second into heat and light. An incandescent bulb will convert most of this energy into heat, and not produce much light, whereas an LED bulb will turn nearly all the energy into light, producing very little heat. This is why LED bulbs are so much more efficient than incandescent bulbs.


So how do you know what "wattage" bulb to buy?


The long answer is to compare light output, measured in candelas, or more properly, lumens. For example, a 5W 12V LED bulb may have a light output of 400 lumens. To produce 400 lumens from a 12V halogen bulb, the bulb might use 50W (50 joules per second) of electrical energy. So a 50W halogen bulb may be replaced by a 5W LED bulb.


However, as a rough rule of thumb, if you choose an LED bulb which has a tenth of the power rating of the halogen bulb it replaces, or a fifth in the case of an incandescent bulb, you will generally be on pretty much the right track: so a 60W bayonet incandescent bulb can be replaced by a 10-12W LED, or a 50W halogen bulb by a 5W LED. In practice, we've found using this rule of thumb leads to a slightly brighter overall effect, which may be explained by the difference in colour temperature.

Case Study: Peter & Helen

Peter and Helen had their house rewired three years ago when they moved in. The electrician fitted 12V halogen downlighters in their kitchen and Helen's art studio. However, in use, the lights generated so much heat, and burned through so much energy, that Peter and Helen found they weren't using the downlighters at all!


Devonia Electrical advised Peter and Helen on various options for replacing their halogen lights. We then test-fitted both warm and daylight bulbs in the kitchen and art studio so that Peter and Helen could see exactly what the overall effect of the different LED bulbs would be. Peter and Helen found that warm LED bulbs produced a light that was similar in tone to their old halogen bulbs, but was clearer and more even.


Peter and Helen had 12 halogen bulbs replaced in the art studio, and 4 in the kitchen. In the studio, the overall power consumption of the 12 halogen bulbs had been a whopping 600W. Using the bulbs for 6 hours per day would consume 3.6kWh of electricity daily, at a cost of around £210 per year.


In contrast, the 5W LED bulbs would reduce this cost by a factor of ten, to only £21 per year. Over the projected lifetime of the bulbs, the energy cost saving is an amazing £216 per bulb - or £3,456 across the whole project!


So Peter and Helen benefit from far lower running costs, a more pleasant and even light, very infrequent bulb replacement, and a great benefit to the environment - but the main benefit is that they can actually use their downlighters without worrying about the cost and heat!

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