How to switch to LED lighting

In the late 19th Century a whole bunch of men independently invented the incandescent light bulb.


Incandescent means ‘emits light when heated’. Because these bulbs need to be hot to work, they use much more energy than they emit as light. Nowadays, alternatives to the cheap and cheerful light bulb abound.

However, converting from incandescent bulbs can be a daunting job – not least because on-line guidance is complicated and, generally, incomplete. This guide covers three key aspects of switching to LED – is it the right decision, choosing your bulb and how to change your lights. I also give some examples of the changes I have made.

Is changing to LED the right decision?

Three factors helped me decide which bulbs to change to LED and when to use compact fluorescents (CFLs).
1. The amount of use. The lights we use frequently have gone to LED and the lights we occasionally use – such as the one under the stairs – I replaced with a CFL. I had a bag full of CFLs that I gathered from my electricity company or special offers. Otherwise, I would have waited for the incandescent bulbs to blow and replaced them with LEDs.
2. Energy use. We have a smart meter and found that our energy use shot up when we turned on halogen lights in the bathroom or kitchen. While we may not use these lights often, there are many of them and they are expensive to run, so we are changing them to LEDs.
3. The quality of light. In our utility room and next to our bookcases we have gone LED. The light is so much better than the old incandescent or CFL bulbs. Now we can see what we are doing and the book we are choosing.

Whether you are changing for cost or the environment, swapping out a working bulb that sees little use is unlikely to have the impact you desire. You then might decide to swap it anyway – after all, you will change it eventually and might as well save money now. Alternatively, you could wait, even better bulbs will be available with each passing month, and the price should drop further.


Table 1: running costs, payback period and lifecycle of different types of light bulb
*Halogen lamps are incandescent but a bit more sophisticated than the old-fashioned light bulb.

The green table shows that replacing a 60 watt incandescent bulb with a 10 watt LED hugely decreases your energy consumption. If you use the light for two hours a day, you will recoup your investment in 400 days. However, if you are updating the bulb under the stairs (unless you already have one lying around), then the bulb may never pay for itself. Environmentally, modern bulbs use a lot of energy and materials to make, so if the bulb spends most days in the dark, then the carbon savings may be negative.

Because LEDs carry a higher price tag, they take longer to recoup their costs than CFLs. Yet many people are choosing LED – why is that? There are quite a few reasons: CFLs contain mercury and are increasing difficult to recycle (from a consumer perspective). They also provide a less pleasant light, can be slow to warm up and have higher upfront costs. Most importantly, six CFLs will blow out in the time it takes the LED bulb to die. Over the life cycle of one LED bulb the difference in life changes the costs (and environmental impact). You can see the cost of 50,000 hours of lighting with each type of bulb in the blue table (assuming you pay 15p for each kilowatthour of electricity).


Table 2: Costs over 50,000 hours of life

If you already have a CFL, you have a judgement call to make. Changing them for LED is expensive, uses more resources and is barely more energy efficient. At the same time, you may not like the quality of the light or the time the bulb takes to warm up. The choice is yours. Please remember that CFLs should not be put in your dustbin as they contain mercury.

Choosing your LED bulb

So you have decided to change to LEDs. Believe it or not, the fun has yet to start; once upon a time the biggest decision about buying a light bulb was choosing its energy consumption and, as energy has become so important, you might think this is still the biggest decision. However, like so many things in life even buying a lightbulb has become more technical. You are going to face lots of numbers, but be brave. These numbers will help you get exactly the lighting you need.


Unless you are going to change your fitment (see How to change your lights) you must replace the bulb with one of the same fitment:
E (Edison screw) either 14 or 27
B (Bayonet) either 15 or 22

bobbly-pinsGU10 – full voltage halogen spotlights, the one with the bobbly pins
straight-pinsMR16 – 12volt halogen spotlights, the one with the straight pins (changing MR16 spotlights is not straight forward, see How to change your lights)


When we choose our wattage in the days of hot lightbulbs, we were most often deciding how bright we wanted out lights to be. Now we are offered lumens. Lumens is a better indicator of brightness as it shows the amount of light coming out of the bulb. But it leaves the first-time buyer unable to work out exactly what they need. The pink table shows the lumens produced by different types of bulbs and their and power consumption according to ‘Which’.


Table 3: Wattage and lumens compared
NB: Because energy (wattage) is an inexact expression of brightness you will find lots of different values in lots of different places – this is a problem caused by the old lights, not the new ones.

Colour aka warmth

Some companies do not use numbers to tell you how warm the light is from your new bulb. They use descriptions like ‘warm’, ‘natural’, ‘cool’ and ‘daylight’. Unfortunately, these descriptions differ between manufacturers, retailers and sometimes the even style of bulb. Ask for the numbers. In the orange table, ‘Which’ gives the following explanations of light colour.


Table 4: How to interpret the colour of an LED bulb

Energy rating

Okay, they are not numbers, but it is worth making sure that your new bulb has a good rating. I would only buy A+ or above, as I am trying to save money and reduce my carbon footprint and a less energy efficient bulb will help me do neither.


The adage ‘you get what you pay for’ has never been more true and less true at the same time. It seems obvious that a bulb selling for less than half the price of equivalent bulbs is unlikely to benefit from rigorous R&D, the best materials or robust manufacturing practices, at the same time there are bulbs out there that cost over £15 each. Practice discretion when buying and read reviews – be the savvy shopper you know you are.


Look for warranty. As with any feature, it is up to you to decide how much you are willing to pay for it. There are on-line retailers offering five-year warranties – if you leave the bulb on all day, every day for five years you will get close to the 50,000 hour life you can expect from a high-quality bulb.

Where should I buy?

Personally, I would love to buy from a specialist hardware shop, where the person behind the counter (ideally in a brown overall) has done all this research for me. But that isn’t going to happen. Instead, we have lots of choices; DIY stores, supermarkets and retailers from Ikea to Poundland all stock LED bulbs, but the chances of anyone being able to help you choose the right one is pretty much rock bottom. You can also buy on-line. There are several specialist outlets, that can provide guidance (I have used two to date, and they are okay). Of course, you can also buy from any number of general, on-line retailers. Shop wisely; these bulbs should last you a couple of decades or longer, so it is worth the effort to get the right one.

(There are more numbers, such as CRI, but you are getting into specialist territory there and most domestic bulbs do not carry this information.)

How to change your lights

The easy jobs

For some bulbs, this job is the same as it ever was. Buy the right bulb, safely access the light (make sure it is off and cool), remove the bulb and fit the new one. If you are replacing a bulb with a screw or bayonet fitting that is all there is to it.
Even some spotlights are easy. If your spots use GU10 halogen spotlights, the ones with the bobbly pins, the job is the same.

NB: there are many more halogen spotlights than those mentioned here, GU10 and MR16 are simply the most common. If your old bulbs have 12 V printed on them, then follow the instuctions for MR16 bulbs. Otherwise check with a specialist retailer.

 The less straightforward jobs

However, if you have MR16 halogen spotlights, the ones with the smooth legs, the job is not straight forward. (MR16 are also called GU5.3)

Between the mains cable and the bulb you have a transformer. It normally nestles in the roof space, and you need a ladder, a friend and very bendy wrists to get to it after turning off the electricity (the friend is going to hold the bulb, lamp holder, transformer and wiring as you remove them from the ceiling).

Just like a phone that charges slowly with the wrong charger, LEDs don’t work so well with the wrong transformer. You can just give it a go, swap the old halogen spotlight for an LED. If it works and continues to work; then you might be okay – or it might burn out early. The best thing to do is to swap the old transformer for a new ‘LED driver’. Changing the transformer is not a job for an amateur. Since your lights went in, the wiring regulations have almost certainly changed, and you need to match the driver to the bulbs you want to use. Call an electrician to work out what is needed to make the change safely.

You might decide now is the time to change from MR16 to GU10. That will eliminate the need for a driver. But this job must only be carried out with an understanding of the wiring regulations.

Panels and flush lights – if you are changing a full voltage fitting for another full voltage fitting or a low voltage fitting for another low voltage fitting, you may feel able to do the job with the help of a DIY manual or on-line guide. But if you don’t know what the words above mean or you are putting in a fitting with a different voltage, then call an electrician.

To be clear, for the less straightforward jobs consult an electrician. If you are likely to do a bodge job and attempt to blame me, then CONSULT AN ELECTRICIAN. You might be god’s gift to electricity, but if your wiring or knowledge is out of date, then you may make a dangerous or costly error, so consult an electrician.

The changes I made

Bathroom spotlight (replacing one 50 W, MR16 halogen spotlight): I bought an 8 W, 640 lumens spotlight; it seems much brighter than the bulb it replaced. That could be because our previous bulbs did not produce as much light as they should, or because of colour. The colour of the bulb is ‘cool white’ (4,000 kelvin). I used the existing transformer, which was okay for a while, but the bulb has now started to flicker. I have bought a 15 W driver and will replace the transformer shortly.

The nice bright lights in our utility and next to the bookcases are 18 W, warm white. They are 1390 lumens bright and produce either 2,700 or 3,000 Kelvin (depending which bit of the retailer’s website you believe). They seem much brighter than the 100 W incandescent bulbs we changed out.

For uplighters in our lounge and hall, we bought 5 W, warm white (2,700 kelvins) frosted candles producing 380 lumens each.

For our study, we bought 5 W, cool white (5,000 kelvins), frosted candles producing 420 lumens each.

With the guidance of an electrician, we will shortly swap out most of our MR16 fittings; there is much work to do. We bought 5 W, cool white (4,000 kelvin) spotlights producing 445 lumens each. They are said to be the equivalent of 43 W halogens, but I expect they will be much brighter.

I know that lightbulbs are really called lamps, but really who says that?

Have fun

References and attributions

CFL image By Sun Ladder – Own work, CC BY-SA 3.0,
LED lamp image By Photo:My Self – Own work, CC BY-SA 3.0,
Halogen lamp image Public Domain,
Incandescent bulb image By KMJ – de.wikipedia, original upload 26 Jun 2004 by de:Benutzer:KMJ, CC BY-SA 3.0,
Lifecycle incandescent, CFL and LED.
Lifecycle halogen,review-1986.html
Lumens, power comparison and light colour
The wiring regulations


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