FAQs - LEDSmiths Experts Answer Common Questions

Below are the answers to a few questions we have been asked over the years that we think may help you get off to a great start when choosing the right LED bulb for your fitting.

What is an 'LED'?

'LED' stands for Light Emitting Diode.  It is really the combined aspect of an LED and an internal driver that we call an LED these days, however for this FAQ we will leave out the technical details of the LED driver.  For more information about this please see our blog.

An LED is an energy saving light bulb that can, at the moment, save up to 90% of your electricity compared to the old traditional style incandescent light bulbs (or "lamps" as the industry terms them).

An LED retrofit bulb, meaning an LED bulb that looks and directly replaces what is planned to be replaced, ranges from under 1 watt for some LED G4 capsules to almost 20 watts for some LED GLS shaped light bulbs. (GLS stands for General Lighting Service, however you may know them more as your traditional light bulb shape).

The LED technology started out as little diode capsules, however it has moved on so far since those days at school connecting them to batteries.  They now come in the shape of an old traditional filament and look similar to the old style light bulbs and some are far more and aesthetically pleasing.

What is a 'Watt'?

A 'Watt' is one of the derived S.I. units (S.I is an abbreviation of the french phrase - Système Internationale d'unitéstranslated as 'The International System of Units, which is the modern form of the metric system and is the current system of measurement).

Watts measures power and although there is no need to go into technical details, it very simply means how much power is used by the LED or traditional bulb.  Watts used to mean how bright the bulb was and if you increased the wattage, then you increased the brightness of the room.  As an example, if you had a 40W candle lamp and you decided that the lamp wasn't bright enough then you could change the light bulb to a 60W and it would be brighter.  Unfortunately with LEDs it isn't quite as simple.

Nowadays you can't look at wattage and say that a 5W LED is definitely brighter than a 4W or a 3W LED because it might not be.  That is because of the LED driver that powers the LED chip inside the LED.  If a manufacturer cuts corners and decides to choose a low quality LED driver then that LED might end up being a higher wattage than similar LEDs which produce the same light output or lumen.  The key to LED brightness is to look at the lumen value on the LED packaging (required by law to be written on the packaging twice the font size of the wattage so you should not be able to miss it).

What is a 'Lumen'?

A lumen is also one of the derived S.I. units described above.  Lumens are the measure of illuminance.  Essentially lumens measure how bright a body of light is.  If an LED claims a lumen value of 806lm, then it is brighter than an LED that claims a lumens of 470lm.

In terms of 'old money', the following table of lumen values are the equivalent to the old light bulbs, the old style wattage is on the left and what that lumen value is:

Non-Directional Lamps:

Power Lumens
15W 150lm
25W 250lm
40W 470lm
60W 806lm
75W 1055lm
100W 1521lm
150W 2452lm


Directional light bulbs, spotlights, have a different set of values and are detailed out in a section below, lumens do not apply to directional bulbs, these are governed by a new measure called 'Useful Lumens'.

In conclusion lumens are now the most important part of the light bulb when considering what you are looking to replace and once you understand lumens, it takes the difficulty out of buying LEDs.  If you are looking for a 60W replacement, just search our website for 806 or just 60W and it will bring up all the 60W equivalent LEDs available to you.

What are 'Useful Lumens'?

Useful Lumens is the new term dreamt up by the EU to blur the lines between the old way of measuring direction bulbs 'Candela' and the way of measuring non-directional bulbs (eg GLS, golfballs and candles) via 'Lumens'.  Useful lumens is a great way to work out what is a good directional LED and what isn't a good directional LED.  Whereas 'Lumens' measures the whole light given off by a light source, 'Useful Lumens' only calculates the lumens in a particular angle in front of the bulb.  Any lumens that are outside this angle, are deemed to be 'wastage' light and therefore aren't counted in the 'Useful Lumens' figure.

This does separate the wheat from the chaff when it comes to sorting out LED bulbs.  Take for example, 2 LED bulbs that both have a lumen figure of 500lm.  However Bulb A has a directional value of 120° and Bulb B has a directional value of 45°.  Most of Bulb A's light is directed sideways, rather than downwards and therefore isn't considered a particularly good light source for a ceiling light, and therefore actually has a 'Useful Lumen' value of 200lm.  Bulb B on the other hand has almost all its light directed forwards, it is considered a perfect bulb for a ceiling and has a 'Useful Lumen' value of 450lm.  So you can see the difference in these 2 examples, Bulb B is good for ceilings, and Bulb A is good for general light.

Below is a set of tables laid out by the EU regulations governing lighting that covers the 'Useful Lumen' values for directional light and their equivalents for each type of bulb.  For example for a manufacturer to call a GU10 LED a 50W equivalent it must have at least 300 'Useful Lumens'.

GU10 240V

Equivalent Power Useful Lumens
20W 90lm
25W 125lm
35W 200lm
50W 300lm

MR16 12V

Equivalent Power Useful Lumens
20W 180lm
35W 300lm
50W 540lm

R50 240V

Equivalent Power Useful Lumens
25W 90lm
40W 170lm


R63/R64 240V

Equivalent Power Useful Lumens
40W 180lm
60W 300lm


R80 240V

Equivalent Power Useful Lumens
60W 300lm
75W 350lm
100W 580lm


Can I replace my old light bulbs with new LEDs?

Yes you almost certainly can.  At the time of writing, almost all of the old style light bulbs are able to be replaced by LEDs.  There are regular technological advances which also mean that LEDs have fallen in price and increased in quality.  The old LEDs didn't do the current range of LEDs any favours however and many people have a poor opinion of LED bulbs.  They used to be expensive, not very bright, claim to have 50,000 hours life, were an extremely harsh white light and didn't look like the bulbs they replaced.

Now you can't even tell that an LED is an LED.  They even look like the old style light bulbs, and you can often choose the colour you want.  They can come in warm white (the old style light bulb colour) to suit your home, cool white to suit your kitchen or office if you have gone for a crisp clean look, or daylight that is perfect for craft work or for SAD sufferers.

You just need to make sure that you choose the right lumen value and the right colour that you need.  If you need to refer to the above tables for lumen values then please do, this will ensure that you get the right bulb for your fitting.  If you have any questions then please get in touch with us.

Can I swap my Halogen MR16 bulbs for LEDs?

The simple answer is yes you can swap them directly for LEDs.  However there are a few things to consider.  First, are the MR16 bulbs on a dimmer switch?  If they are then it may be a costly exercise to swap them over.  We will start with talking about the MR16s that aren't going to be on dimmer switches.  In order to work correctly, it all depends on the transformer that the bulbs are running on.  If you don't know what a 'transformer' is then it is the little box in the ceiling that the 12V light bulb is connected to.

Please note that LEDSmiths always recommends that you use a qualified electrician for any electrical work and the advice below is for electricians and competent people.

The transformer will say a lot of information on it, however the key information is the writing that is a few numbers that has the suffix (the bit on the end) that follows some numbers of 'VA'.  This stands for Volt Amps, this is simply the wattage of the bulb divided by the 'Power Factor'.  For ordinary bulbs or the standard halogen bulbs the power factor is actually 1 so when you look at the VA you may have just in the past directly converted this to Watts.

Halogen Example:

The transformer says output - 10 - 60 VA.  This in halogen terms would just mean that it runs an output of 10-60 watts of bulbs, so you could put 3 x 20W halogen bulbs on, or 1 x 35W bulb or 1 x 50W bulb.  Unfortunately with LEDs lamps it isn't so simple.

LED Example:

The same transformer says output - 10 - 60 VA, however the LEDs that you have are only 5W.  You might not think that it would work, however the low voltage LEDs tend to have a low power factor, so they might be 5W but have a power factor of 0.4 (not 1 like halogen bulbs).  This means that in VA terms, that 5W LED bulb looks to the transformer more like a 12.5W light bulb, so it should run perfectly on your transformer.  This means you can put 4 of these bulbs on this transformer and it should run perfectly.

Adding dimmable into the equation.  Unfortunately coupled with the above, you also have to do the same calculations when working out if the LEDs will be compatible with your dimmer switches.  In the past there may have been a theory that you can only install 10% of the total wattage the dimmer states, so if the dimmer says on the back of it, min 0W, max 250W, you might think that you can only put up to 25W of LEDs on this dimmer.  The best thing to do is consider the power factor as above.  If that 5W LED has a power factor of 0.4 and you want to use your 250W dimmer but you don't know how many bulbs you can put on then do the following:

Divide the wattage of the LED by the power factor - 5W ÷ 0.4 = 12.5

Now take the dimmer max rating and divide it by the number you got as the result above - 250 ÷ 12.5 = 20. 

This means you should be able to put 20 of the above lamps on the dimmer circuit without any problems.

The only other factor to consider is whether the dimmer will be ok for your bulbs.  IMPORTANT - NOT EVERY LED BULB WILL RUN ON EVERY DIMMER SWITCH.  Even dimmer switches that claim to run LEDs, may not run every LED.  It is important to get in touch with the manufacturer of the LED, or browse their website, to find out if it is compatible with your dimmer switch.  Some dimmer manufacturers publish which bulbs will run on your dimmer.