If you’ve still to upgrade your halogen MR16 spotlights to LED MR16, time is running out.

In September 2016, the European Commission directive banning the manufacture of ‘high-energy’ halogen spotlights came into force. These light bulbs are now becoming increasingly difficult to find as retailers sell through the last of their stock. This guide will tell you everything you need to know about replacing Halogen MR16 bulbs with LED bulbs.

Fortunately, upgrading Halogen MR16 light bulbs to LED is usually a painless affair, as most LED light bulbs are now designed to retrofit to existing light fittings. All you have to do to swap your old bulbs out is remove them from the light fixture and fit the new, shiny bulbs in their place.

The same goes for low voltage spotlights, but as they use transformers to convert mains voltage to a suitable lower one, you have to be careful to install the right LED light bulbs.

Crompton Lamps LED 12V Constant Voltage Driver 20W

Replacing Halogen MR16 light bulbs with LED MR16 light bulbs

If you have low voltage halogen light bulbs installed with a transformer, the first thing you need to do before replacing Halogen MR16 light bulbs with MR16 LED bulbs is to find the transformer’s maximum load. You should be able to find this on the body of the transformer itself, in the form of a ‘VA’ number. This VA number will either be fixed, or it will be a range (e.g. 10-60VA).

These numbers tell you the maximum wattage that the transformer can carry. For example, a 40VA transformer can handle up to a 40-watt halogen light bulb, while a 10-60VA one can carry between 10 and 60 watts worth of bulbs. Some transformers might just carry one individual light bulb, while others might be able to carry several lower wattage light bulbs in a series.

At this point, it’s important to note that if it is a halogen transformer, this maximum load applies to halogen light bulbs only. For example, if you have a 40VA transformer for halogen bulbs, you should not install 40-watts worth of LED light bulbs. This would overload the fitting and potentially cause a safety issue.

Fortunately, there is an easy way to find the right low voltage LED spotlights.

Osram LED MR16 Spotlight 8W GU5.3 12V Dimmable Parathom Cool White 36°

Equivalent wattage – swapping halogen MR16 light bulbs for LED MR16

The natural energy-saving properties of LED light bulbs means that they can offer the same brightness of a halogen equivalent, but using only a fraction of the power. A 5W LED spotlight, for example, can offer the same brightness of light as a 35W halogen spotlight.

The 5W LED light bulb is the ‘equivalent wattage’ of the 35W halogen light bulb. You can usually find this equivalent wattage listed with online product details, specification sheets (where available), and on the product packaging.

When replacing Halogen MR16 light bulbs with LED bulbs, it’s important to use LED bulbs of equivalent wattage to your existing halogen light bulbs. This will ensure that the transformer can still handle the load safely.

For example, if you have one 35W halogen installed in your kitchen, ensure you swap it for 35W equivalent LED. The actual wattage of the LED light bulb may vary, but the equivalent wattage must be the same as your current halogen bulbs. For example, you might find both 5W and 6W LED light bulbs that have an equivalent wattage of 35W; both of these would be fine to replace 35W halogen bulbs.

This is only getting more complicated as LED technology gets ever more energy-efficient, but as long as you remember to look for the equivalent wattage, you will find the right LED spotlights. We’ve finished our guide off below with a quick ‘cheat sheet’ to help you remember all the technical terms discussed above. See our in-depth glossary of lighting terms for even more information.

Equivalent Wattage

A term used to compare LED light bulbs with their incandescent alternatives. An LED light bulb with an equivalent wattage of 35W is a direct replacement for a 35W incandescent light bulb. This is different from a light bulb’s stated wattage (see below).

Halogen MR16 Spotlights

Spotlights are ‘directional’ bulbs that emit light in a focused beam. Halogen spotlights are a form of incandescent light bulb that use a tungsten filament and a mix of inert and halogen gases to produce light. The European Commission directive in September 2016 banned the manufacture of this type of power-hungry spotlights.

LED MR16 Spotlights

LED (light-emitting diode) light bulbs are the most technologically advanced and energy-efficient bulbs available. They last many times longer than halogen light bulbs, produce the same amount of light, but use only a fraction of the energy. Most LED light bulbs can be used with existing light fittings (this is called retrofitting).

Low Voltage

Most light bulbs operate off mains voltage (see below), but some light fittings are designed to be lower voltage. These are most commonly used in integrated kitchen fittings, where space is at a premium and smaller bulbs are a necessity. Low voltage light fittings often need a compatible transformer (see below) to convert mains voltage to the correct, lower voltage. Most low voltage spotlights will be between 12-24 volts.

Mains Voltage

The voltage of a building’s electrical circuits. In the UK mains voltage was 240 volts until late in the 20th Century, when it was changed to 230V to match other European countries. As this comes with a +10% tolerance, electrical equipment with a stated voltage of 240V is still fine to use on standard UK mains circuits. The majority of bulbs are for use with mains circuits, except for ‘low voltage’ light bulbs, which must be used with a compatible transformer (see below). All low voltage bulbs should be clearly stated as such on product listings and packaging.


Bulbs that operate on a lower voltage than 230-240V must be used with a compatible transformer when installing on UK mains circuits. The transformer converts mains voltage to a lower voltage suitable for the bulbs, ensuring they function as designed and preventing damage to the bulbs and/or light fittings.

VA rating

The volt-ampere (VA) rating is the maximum load (in watts) that a transformer can safely carry. For example, a 40VA transformer can handle up to 40-watts of electrical equipment, while a 10-60VA one can carry between 10 and 60 watts worth. Installing low voltage LED light bulbs on a transformer designed for halogen lighting requires you to find the equivalent wattage (see above) for the LED bulbs, so as not to overload the transformer.

Wattage (or Stated Wattage)

Denotes the rate of power consumption of electrical equipment. A higher wattage equals greater power consumption. LED light bulbs have a stated wattage and lumen output, as well as an equivalent wattage (see above).

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Robert Becker

I have Contrast Lighting IT2000M housing units for recessed lights that have magnetic transformers that originally came with 50Watt MR16 bulbs. I swapped out the halogen bulbs for Feit MR16 6.6 Watt led bulbs. The led’s work however, on two sets of switches I’m experiencing buzzing sounds that go away if I adjust the dimmer down and on other set of lights when I turn them on a whoosh feedback sound can be heard when turning them on. Will upgrading the dimmer switches to led compatible reduced the buzzing and work with the old transformers? Thank you in advance.


Hi, thank you very much for such an insightful article. It was exactly what I was looking for. I currently have halogen mr16 with “ET-E 60 220-240V 50/60Hz” transformer. Would there be any LED mr16 that would be compatible with this transformer? Thank you!

Mat @ Lightbulbs Direct

Hi, this transformer is a Philips transformer and is designed for halogen lamps, so has a minimum load of 20W. This means that it will only work with bulbs of 20W or higher, which sadly isn’t compatible with single LED light bulbs as they are lower wattage than 20W.


I think this article needs to cover Power Factor. It’s not actually true that for all bulbs that a 60 VA transformer can supply a 60W bulb – true for incandescent with a power fator of 1, but not for lower PFs. I recently bought some LED MR-16s, 6W electrical power with 12V 50 Hz AC input (integral converter to DC) and found they had a power factor of 0.4. This means that they needed a supply of 6 W ÷ by 0.4 = 15 VA capacity. So four of these could not be powered by a 60 VA transformer, as that would provide no spare capacity, it would need something like 80 or 100 VA transformer. It’s extremely rare to get a discussion on power factor in info on LEDs.


I currently have 4 halogen 12V 50W 5.3 MR16 bulbs in my downlighters, each running off its own ET60T-3 (20-60VA) transformer.

I want to replace the halogen bulbs with Philips Master Value LED 5.8W MR16 4000K 36D Dimmable (35W equivalent) bulbs. This Philips bulb boasts compatibility with a wide range of transformers.

Would this work, or are the transformers likely to struggle with this bulb?

Mat @ Lightbulbs Direct

I think that transformer maybe too powerful for LED, as its lower range is 20VA, and I calculate 4x 12V 5.8W to be about 2VA


I had a very similar issue. 4 x 6.1W LEDs, needing 12v AC input with integral AC/DC conversion. The transformers, 1 per bulb, are 20-60VA units 12v AC output, originally for 50W halogen dichroics. In complete ignorance of the complexities I just fitted the bulbs and they worked fine, no flickering. Then I found these bulbs had a power factor of 0.4, meaning they needed 6 ÷ 0.4 = 15VA transformers. As 15 is not far below the transformer range of 20 to 60, I am guessing this is why they are working ok.


p.s. it’s almost impossble to find power factor data on LED bulbs without getting the mfrs data sheet. I’ve never seen it on an online shop’s pages. I only tripped over it reading the leaflet that came with my Integral LED MR16s

Mat @ Lightbulbs Direct

Hi Cliff, you are very much correct on all your comments.

MArtin Carter

Isn’t the equivalent wattage on an LED bulb the wattage that a tungsten bulb would have to have to give the same brightness? That has little to do with the actual power consumption. which is what the transformer is interested in. Also, don’t LED bulbs cause a problem with an initial power spike in the transformer as opposed to tungsten bulbs which have a fixed load?

Mat @ Lightbulbs Direct

The equivalent wattage is related to the old technology they are replacing. So as MR16’s are traditionally halogen bulbs, then the equivalent is per an halogen MR16. For both tungsten, halogen and fluorescent technologies, the wattage is directly related to it’s brightness, so when we state an equivalent wattage, then yes, we are saying this bulb is a bright as an old ??W bulb. Typically a 5W LED is equivalent to the brightness 35W halogen MR16. The actually wattage on the LED (i.e. 5W), is the actual power consumption of the LED bulb. LED bulbs can sometimes cause an initial power spike when they are first turned on. This spike is caused by the sudden rush of current needed to activate the LED driver and start the LEDs. It is a short-lived event and usually not a significant concern for most transformers.


I have a 12v low voltage “toidal” transformers in the loft driving 8 to 10 35 to 50w halogen MR16 bulbs, can I replace the bulbs with LED’s? If so what wattage should I purchase?

Mat @ Lightbulbs Direct

I would suggest replacing this transformer is it is not designed for LED and may provide too much power to the LEDs which could cause overheating or other issues. To replace a 35W halogen MR16, we recommend a 5W LED bulb. To replace a 50W halogen MR16, we recommend a 8W LED bulb. We stock a suitable LED compatible driver and you could run 4x 5W LED bulbs off each driver.

Barbara Lemieux

Hello, I live in Canada. I have a Marcus MC100A transformer rated 100VA 120 Volt (pri) 12 Volt [sec). I currently have 3 Halogen MR16 lights with GU5.3 base (each 35 Watts) connected to that transformer. I want to switch to LED lights. Will it be fine to buy 3 LED MR 16 lights that have an Equivalent wattage of 35 Watts?

Mat @ Lightbulbs Direct

This transformer is a bit overpowered for LED, you would need to swap it out for an LED compatible transformer.


Is there an alternative LED lamp for a transformer labelled ‘MR16 12v 50W’ please?

Mat @ Lightbulbs Direct

Not enough information to go there, as we would need the minimum load the transformer can output to see if it LED compatible.


Why are we using the equivalent wattage for LED lamps? I just replaced 3 12v 35w bulbs with 3 12v 4w LED bulbs and it blew my 12v transformer. I get that I shouldn’t have used them but not why. In my head I was sure they would be fine as they where only drawing 4w each and I don’t understand why that would cause the transformer to fail? Why does equipment output wattage cause the transformer to fail are they actually drawing more apparent power, if so are we actually saving money?

Mat @ Lightbulbs Direct

The issue is that the driver is designed for 35W only and is not variable – it is trying to force 35W @ 12V into the light bulb and the light bulb won’t accept this, so one of the components is going to go pop.


How do you tell if a transformer/driver(??) is compatible with LED lamps? I am currently using Halolite HA-SE60 for my Halogen 50W MR16 GU5.3 12V lights can I them for LED replacement?

Mat @ Lightbulbs Direct

Looking up that transformer, and it is rated at 20W to 60W. As LED lamps are less wattage, for example 5W, then this transformer is not suitable as it supplies a minimum of 20W.


Hi, I understand that swapping a Halogen for an equivalent-rated LED but what if it has a lower Equivalent rating? I want to exchange a 12v, 50w (MR16 Gu5.3) Halogen for a 12v, 3w (GU5.3) LED (equivalent to 35w) is this ok?

Mat @ Lightbulbs Direct

Yes, it’s fine. Although, the 35W equivalent LED might not be as bright as a 50W


I have a techmar 12v 20w halogen transformer which has 6 Focus garden light fittings attatched.Can I replace the current bulbs with LED’s and if so can you advise which ones please.Currently I have red,amber,blue and green and would like to replace with colours if possible.

Mat @ Lightbulbs Direct

I don’t think there’d be much problem swapping over to LED, especially coloured LED’s as they are normally very low wattage. Just make sure the total wattage of the 6 bulbs is less than 20W. Sorry, but we cannot help with the supply of coloured LED MR16 lamps as we do not stock any.


We have 10 low voltage mr16 50w lights in our bedroom that are powered by a “toidal”? transformer in the loft, we also have 2 banks of 4 lights on dimmers powered by a similar transformer again in the loft. Can we replace the bulbs wit LED’s? directly without changing the transformers?

Mat @ Lightbulbs Direct

Just looking into a toroidal transformer and I would suspect they wouldn’t be compatible with LED bulbs as many manufacturers recommend the use of an electronic transformer.

Dave Longhurst

Hi I need to replace GZ6.35 100W Halogen with LED any ideas

Mat @ Lightbulbs Direct

We haven’t seen an LED equivalent to this lamp on the market yet – since it is such a specialist lamp, then halogen versions are not part of the halogen ban and can still be manufactured and sold (I’m afraid we don’t have stock these either).


In my bathroom there are 6 low voltage halogen gu5.3’s. I have no idea of their wattage as there are no markings on the the bilbs other than MR16, i have replaced them with 6x 8w LED’s. When you switch them on one us very bright and one is strobing, the rest are dull, any ideas please

Mat @ Lightbulbs Direct

Yes, the transformer in the fitting is not suitable for LED MR16 light bulbs as it has been designed for use with Halogen. Halogen MR16’s are now scare to buy due to being banned (we have no stock), so it may be time you either need to replace your fitting completely or find an electrician who can modify the fitting for LED.

Brent Gardner

Hello, I have recessed spot halogen potlights in my ceiling. They take MR-16 35W halogen bulbs.House was built in 1996 and they are original to that time. Label says 35W max Halogen bulbs. I switched bulbs to LED MR16. The new bulbs work, but some of them are smoldering/smoking and then they stop working after a month. When I remove bulb the connector MR16 plug is a charred blackened lump that looks like it came out of a fireplace. Both bulb and socket are destroyed. I have over 100 potlights and thus far 8 have stoped working burnt out the connection, and 92 are still working without damage. What could be causing this? The transformer(s)? It seems that the LED bulbs are being given too much power through the connection and this is causing (some of) them to burn/melt. The only reason I can think of is that the bulb is being given too much power and is overheating.

Mat @ Lightbulbs Direct

First thing first, this sounds like a dangerous situation and a serious fire risk – I would advise you get an electrician to test those remaining fittings immediately. Although not being an electrician myself, I would suggest you may be right in your assumption. As halogen transformers are rated for halogen use i.e. 35W, they may not be able to output the small power amount that an LED requires. LED transformers output at a typical range of 0W to 10W, whereas a halogen transformer maybe 30W to 100W. It would also be worth considering that the light bulbs are poorly manufactured and could be at fault. Above all, please be safe.


Hi Brent,
Can’t be sure but it sounds like you may have fire-rated sealed fittings in your ceiling. These units require special alumnimum backed halogen lamps – sometimes called ‘ali-back’ or ‘coolfit’.
These lamps can be 50w but must be sourced and fitted as above for ceramic pot type mountings.
You’ll need to replace any wiring and sockets. Standard transformers will be ok.
Another option is to upgrade to cooler running LEDs, and then the transformer must be changed out to a compatible 0-x wattage unit. Wiring and socket should be renewed as well.
Hope this helps in time.

Derek Monahan-Smith

I have 6 downlight fittings in my lounge on a single dimmer switch. I want to replace the current lamps for LED version. The info. on the bulb is LCLEXNE MR16+C 12v 50w 1045.
Can you help with information on the replacement model

Mat @ Lightbulbs Direct

Hi Derek, we don’t offer a LED MR16 in warm white that is equivalent to a halogen 50W, we can only offer 35W equivalent LED MR16 which wouldn’t be as bright.

Catherine Macdonald

I have an existing transformer running two 12V50W recessed adjustable spots with halogen bulbs.
The recessed fittings need replacing, and a switch to LED would be sensible at the same time. But I don’t want to replace the transformer.
Are there any new LED compatible fittings that would work with the existing transformer.

Mat @ Lightbulbs Direct

This depends on the minimum load of the transformer, and whether it is low enough to power a 5W LED. If you do need or decide to replace the transformer, we stock a replacement transformer designed for 12V LED light bulbs.


Hi. i currently use halogen downlights but want to switch over to use LED ones. Can i simply just replace them out? some contractors told me that i cannot do that and must change the whole electrical system or something like that.

Mat @ Lightbulbs Direct

This depends on the driver used in the fittings, and whether it can handle the low loads of an LED. Because a typical halogen spotlight bulb maybe 35W-50W in power, but LED is only 5W, if the driver is not suitable to supply power for a 5W light bulb, then you may run into problems. For these instances we sell a replacement driver designed for 12V LED light bulbs, but you would be best to consult an electrician to fit it.


Thanks, After some research and consultation, i realized that the new LED downlights have built in transformers and thus can be directly connected to the 220-240v line.

steve keene

I have two halogen m32 bulbs that I would like to get in led can anyone help?

Mat @ Lightbulbs Direct

We only stock Halogen version so of this bulb – GY6.35 2-Pin Capsule Light Bulbs

Donald Folley

help looking
for mr16 / 250w 24v Bulb led replacement
thanks in advance


I have replaced a 50w halogen bulb with a MR16 5W 12v LED. I have replaced the driver with an AURORA AU-LED 16T 1-16W constant voltage. The bulb now flashes like a disco. What have I done wrong? 

Mat @ Lightbulbs Direct

Is the lightbulb on a dimmer circuit? I see that the driver you have used is classed as non-dimmable?


No the bulb is not on a dimmer circut, it’s in a bathroom above the bath.

Mat @ Lightbulbs Direct

Hi Alan, I would guess there is a compatibility problem between the bulb and the driver. The bulb manufacturer should issue a list of compatible drivers on their website, so maybe check with the bulb manufacturer for help with this issue.

Alan Thompson

Will do. Thanks. 


I have a 150w 82v mr13 halogen bulb that I would like to replace with an LED but cannot find one anywhere. I am having a very hard time even finding a 150w equivalent LED bulb of any kind. Any help would be greatly appreciated.

Mat @ Lightbulbs Direct

Sorry to say, but I doubt very much that an LED version of that very specific bulb is available, or will ever be available. Bulbs like this are exempt from the halogen ban because of their very specific application use.


Anyone know the answer to this ?…… My lights are 12 volt……20 Watt max…….Halogen…With transformer….. There are 4 lights…… 20w bulb in each one…… MR16….GU5.3…. 50mm wide by 45mm depth
Can I use LED bulbs ……  Also…..Would the VA rating of my transformer be 80…..4 X 20w…….Or would it simply be 20 ?……


i’ve tried replacing my warm led spotlights with brighter led spotlights but they flash on and then go super dim. Can you help explain why that might be?
old bulbs – MR16 5.2W 2700K AC/DC12V 50/60HZ
new bulbs – MR16 5W 6000K AC?DC12v 
I thought 5w vs 5.2w would be fine? please advise


Hi there,
I have recently replaced my MR16 halogens with LEDs around 50 of them. LEDS have an Equivalent wattage to 35.
I have these transformers which have been attached since 2000, see photo below, can you please advise if I have made a mistake in choosing the correct bulbs for the job?
(If there is an issue with upload the transformer states Outputs 12V 1x50VA)
Thanks in advance

Last edited 2 years ago by James
Mat @ Lightbulbs Direct

Unfortunately you image upload didn’t work – for info, the equivalent wattage of the LED’s is irrelevant – what is important is the actual wattage they draw and is the transformer capable of delivering that. You could always try a couple of lightbulbs and see what happens before swapping them all out?


Im sorry but is this not in direct contradiction to what you said in the following paragraph? I promise I am not trying to call you out, just very confused to what I need to do in order to select the correct bulbs.
“For example, if you have one 35W halogen installed in your kitchen, ensure you swap it for 35W equivalent LED. The actual wattage of the LED light bulb may vary, but the equivalent wattage must be the same as your current halogen light bulbs. For example, you might find both 5W and 6W LED light bulbs that have an equivalent wattage of 35W; both of these would be fine to replace 35W halogen light bulbs.” 

So i have removed 50W halogens and replaced them with 5W LEDS which are equivalent to 50W halogens. They work fine but i am worried it will cause a fire so thats why I have asked. 


Mat @ Lightbulbs Direct

Hi James, you’ve got it correct there and have replaced the lamps with the correct type. There shouldn’t be a fire risk.


Hi, I have 17 low voltage halogens bulbs in my kitchen,
Each has its own transformer and the three circuits are controlled by dimmer switches. I have tried replacing the bulbs with Lv less but they flicker.
Do I need to swap the transformers for Led drivers, do the also act as a transformer?. Do I also need to replace the dimmer switches?



Hi. I’m looking to replace low voltage (12v( halogens with 240v LEDs) because of the problems I’ve had with transformers and replacement 12v LEDs. I will remove the transformers from the circuits, so a 240v feed to the bulb. Can I use the existing GU5.3 (MR16) sockets? Will the 240v LEDs still be more energy efficient?

Mat @ Lightbulbs Direct

No, GU5.3 sockets are for use with 12V spot lightbulbs only. You can, however, swap out the GU5.3 socket for a 240V GU10 socket. How easy this is with your fitting, we cannot answer. As for energy efficiency, a 12V 5W MR16 uses the same energy consumption as a 240V 5W GU10.


I have halogen downlights in a bathroom which I’d like to change to LEDs. There is a transformer to each light fitting. It’s a Newlec Dimmable Transformer, Model NLLVLC60D. I have attached a picture of the transformer and wonder if I can use LEDs with it. I’d prefer not to change it. Any help anyone can give me would be most appreciated.

Mat @ Lightbulbs Direct

You may run into problems with this transformer, as it is designed for use with Halogen light bulbs and therefore has a wattage range of 20W to 60W.
As most LED bulbs have a much lower wattage, for example 5W – this falls below the minimum rating that the transformer is designed for (20W).
We would advise you swap out the transformer for one an LED compatible transformer.

Charlie turvey

I am changing the halogen lights in my kitchen for led lights, each light has its own transformer and I have bought some led transformers to replace the existing ones. I have doubled checked that I have wired the new transformer correctly but the bulb flickers with very little light. I have contacted the seller and he says that the bulbs I am using are the problem. I have MR16 5W ac/dc 12v bulbs. The seller says that it is because I am using ac/dc bulbs not dc bulbs……but these seem very difficult to locate…….is this correct

Mat @ Lightbulbs Direct

Do you know what the minimum rating of the new transformer is? It could be that it is from 10W to 100W for example, in which case a 5W MR16 is below the minimum rating.


I have 5x MR16 12v 50W halogen lights in the kitchen which I’d like to replace with LED ones. Each light has an Aurora transformer 20-60W/VA so I don’t think they will work with 8W equivalent LEDs. I saw you suggest replacing the transformer with a “Crompton Lamps Driver 10W 240V to 12V”. However, instead I’m thinking of switching to 240V 8W LEDs, my question is, can these go into the existing housing in the ceiling, and what fitting do I need to connect the back of the 240V LED to the connection block that the old transformer currently goes into? Thanks.

Mat @ Lightbulbs Direct

You can possibly get a qualified electrician to remove the transformer and MR16 lamp holder and replace with a GU10 240V lamp holder, this will allow you to use 240V LED GU10 light bulbs – but this is dependent on the fitting and how accessible it is to modify. We must stress that we would only recommend a qualified electrician to modify any fitting. You are correct in that the Aurora transformer you have will not work with 8W LED’s as the transformer is rated to only work with lamps between 20W and 60W.


I have 9no. Mr16 halogen Spotlights downstairs which say 12v 35w on them. I replaced them with 3w/20w equiv led bulbs and 8 work fine except one which flashes on when I first turn them on but then goes off. It still works fine with halogen and all the others are unaffected no matter what’s in it. I now have 8no. 3w led and have just left that empty rather than put a halogen in but would like it to work. Any advice?

Mat @ Lightbulbs Direct

Hi Will, the most likely source of the issue will be a compatibility problem with the 12V transformer that resides in your fitting. If the transformer was designed to work with halogen lightbulbs then it may have an issue in providing the lower power supply that LED bulbs require. We have found that some transformers are rated for use between 100W to 400W for example, so where 100W is fine for halogen (equates to 3x 35W halogen) this figure is not met with 8x 3W LED light bulbs (24W < 100W). Obviously we cannot comment on your specific transformer, but we have advised customers in the past who run into this problem to keep 1x halogen light bulb in the fitting which helps to increase the overall power consumption so it falls into the tolerance range of the transformer. Outside of that advice, any other fix requires replacing the transformer in the fitting with a suitable LED transformer, or replacing the fitting entirely (for which we would then advise to purchase a fitting that uses 240V GU10 spotlights as these don't require a transformer).


I’m considering changing our existing spots in the house to LED which are MR16 50W halogen bulbs connected in a series of 3 to an Aurora AU-150 transformer rated 50-150VA. We’ve got quite a lot of these throughout the house and if possible I’d like to avoid replacing these (due to the cost) with an LED driver equivalent. Would the existing transformer work with cool white 4000K LEDs? WWe don’t use dimmer switches at the moment but it would be a nice option – we have double switches at the moment.

Also I presume a reasonably competent (non-qualified) person can do this (taking appropriate precautions of course inc. turning off the mains supply).

Thanks in advance for your help.

Mat @ Lightbulbs Direct

Hi Rakesh, So that specific transformer is rated to work between 50W and 150W – this means that the minimum load that needs to be used is 50W, and the maximum load is 150W. As a typical LED MR16 spot light bulb is only 5W, then three of these will equal a load of 15W which is outside the scope of the rating of the transformer. I am afraid that this could cause problems (such as flickering) as the transformer needs a minimum load of 50W.

Lynsey Ellis

Hi I have just replaced GU10 50W halogen bulbs with GU5.3 5W LEDs. 3 separate spot lights in my bathroom. 1 is ok but the other 2 flicker. What am I doing wrong? Do I need lower watt led bulbs?

Mat @ Lightbulbs Direct

It sounds like transformer in the fitting may not be suitable for LED – Some transformers are designed to run halogen spotlights and are thus rated for 50W – 250W for example. As LED lightbulbs use much less power, e.g. 5W, then your total power is only 15W. This could be less than the transformer in the fitting is designed for. You can potentially swap the transformer out, but as this requires an electrician to carry out, it is not cost effective and you may just wish to replace the fitting. We do sell a 10W LED transformer suitable for running up to two 5W LED GU5.3 spotlight bulbs, but you would require two of these to be wired into your fitting to run three 5W light bulbs. An alternative “fix” is to swap one of the LED bulbs out for a halogen GU5.3, which will then take your power output above the lower end of your transformer and the flickering will stop.

Lynsey Ellis

Thanks for the advice

John Hopper

I had 3 xhalogen 50w mr16 bulbs run by a 150w transformer. Will led mr26 bulbs work the same

Chris Perry

Hi. I’m looking to replace low voltage (12v( halogens with 240v LEDs) because of the problems I’ve had with transformers and replacement 12v LEDs. I will remove the transformers from the circuits, so a 240v feed to the bulb. Can I use the existing GU5.3 (MR16) sockets? Will the 240v LEDs still be more energy efficient?
Thanks for your help


I currently have down lights with Osram decode 51s (12V 50W) halogen bulbs. Each light has a dimmable 60VA transformer connected. Could you please advise on a suitable replacement dimmable LED bulb?
I guess an alternative would be to fit new GU10 lamp holders with LED bulbs and ditch the transformers. Do you think thy is would be a better approach?
Many thanks

Mat @ Lightbulbs Direct

We no longer stock Osram 12V MR16 halogen spotlights but we so stock replacement LED dimmable MR16 spotlights – the choice is yours really.

Last edited 1 month ago by Mat @ Lightbulbs Direct

I have a HiSpec HSE60L transformer. It says 60W max on with SEC: 11.8V~eff. I’m wanting to change to LED bulbs. There were 3 bulbs installed and now I have 1 left. When talking about the equivalent, does this mean each bulb can only be a maximum of equivalent 60W overall (I.e. equivalent 20w each) or can it be equivalent 60W per bulb?

Mat @ Lightbulbs Direct

It means the wattage of all the bulbs added together (not equivalent), if there’s 3x LED bulbs @ 5W each, then that = 15W. However, I cannot find any information on this specific driver, so I’m not sure if it is LED compatible or not.


Thank you


I am currently looking to replace the halogen MR16’s in my daughters room which are currently 12v 50w on individual transformers. Can I change these for 35w equivalent MR16’s or do they need to be 50w equivalents.

Mat @ Lightbulbs Direct

You may run into problems depending on the transformer that is installed in the fitting. If the transformer is designed for use with 50W halogen type bulbs, then it may not be rated to work on lower powered lightbulbs. For example, a typical transformer may only be rated between 50W – 250W – if you install a 35W bulb then it will not draw enough power to be used on such a transformer. This problem is exasperated when such a transformer is used with LED lightbulbs that may only draw 5W of power. The easy answer is to stick to 50W only.


currently have 21 (old 30 watt) halogen spots, 3 to a transformer. Can I just change to led GU 5 bulbs or do I have to remove transformers ?

Mat @ Lightbulbs Direct

This depends on the capabilities of the halogen driver. As halogen consumes much more power than LED, the driver may not support lower powered lightbulbs. Never fear, as we stock a replacement 12V driver for LED lightbulbs.


If you replace to an LED driver do you need to change the old dimmer switch on the wall though?


Hello.. Is it possible to replace Type T 40W Halogen Bulb in a lamp to a LED light? Would appreciate your answer!

Mat @ Lightbulbs Direct

Yes, you can swap an Halogen Type T for LED, but they are quite hard to find LED versions. We stock a range of halogen ones if you cannot find one: Tubular Shaped Light Bulbs

Last edited 1 year ago by Mat @ Lightbulbs Direct
Eric Atkinson

I am wishing to replace halogen light bulbs in my shower room with LED ones, I am finding that the LED bulbs are strobing after a few minutes of being switched on. Do I need to change the transformer?

Mat @ Lightbulbs Direct

It is likely that the transformer cannot be replaced, as a shower fitting should be water-tight for obvious safety reasons. I would advise replacing the whole spotlight to a waterproof (IP65) rated fitting with an integrated LED, which would eliminate this strobing problem plus give you confidence that you have a safe product to use. We have a range of ceiling downlights suitable for bathrooms. Something like the Phoebe LED Firesafe is a great choice as it comes with inter-changeable bezels (white, chrome, brushed nickel), is fully dimmable, and has a switch under the bezel so you can choose your favourite colour of light – warm white, cool white or daylight.

Last edited 1 year ago by Mat @ Lightbulbs Direct
Peter Chappell

I intend to replace all my Halogen MR16 Dichroic spotlights as I am fitting covers in the loft and need aluminium reflectors or the heat build up is too great. Good opportunity to replace with LED spots. Are these equivalent to aluminium reflectors and do not allow heat to emit from the back of the light?

Mat @ Lightbulbs Direct

Yes and no, well, not in the same way. Dichroic reflectors have a coating which reflects all visible light and IR light (heat) forwards out of the front of the lamp; and as they are halogen lamps, they generate ALOT of heat. LED are different in that they don’t generate that much heat in the first place. Typically most LED’s are cool enough to touch even after being run for many hours. I don’t think you would find much problem using LED MR16’s under a loft hood, especially some of the newer models which are even lower power than the first generation of LED MR16’s. Something like Crompton’s glass LED MR16 Non-Dimmable would be most suitable. But if you want a dimmable version they will cost more – browse our MR16 range for comparison.



Tom Kilgllen

The LED bulbs I bought seem as though they will be fine in my current MR16 housings. The existing lights are running through a Low voltage dimmer.
My question is – I would think I need to leave the low voltage dimmer instead of switching it to an LED dimmer. As far as I know, a standard LED dimmer is not low voltage. Do they even make an LED low voltage dimmer? Do I need it?

Thank you!!

Mat @ Lightbulbs Direct

Hi Tom, this very much relies on the quality of your transformer. The dimmer switch acts by cutting the power on/off very rapidly, but it is down to the response of the transformer in how this is relayed to the MR16 lights. My only advice is to take advantage of a supplier’s returns policy to try some products out on your own set-up. Remember to keep the packaging in a re-saleable condition and understand that you will probably have to cover the cost of return postage if you order from an online retailer.


I have high voltage halogen bulbs installed with a transformer. Do I need to change the transformer if I want to retrofit new LED lights into existing fixtures?

Mat @ Lightbulbs Direct

What voltage is high voltage?

The LED light bulbs we sell operate on a UK standard 240V AC, and the light bulbs have a built-in transformer to change this 240V to the LED required voltage.
We also sell 12V light bulbs, but these need to be used in conjunction with a 12V transformer.

John Dowell

I have 2 gu4 halogen bulbs in my fireplace. I’ve tried to replace with two led bulbs. When I install the new led bulbs they dont work. If I leave one led bulb in and install 1 halogen bulb in the led light lights up. The halogen bulb does not.

Why is this ?

Norman Dunbar

Sounds like the load on the transformer isn’t high enough to keep the power on. I have a similar problem. Apparently you can either “put a load resistor” on the output or keep one halogen bulb in the circuit. Kind of defeats the purpose of replacing with LEDs!

Mat @ Lightbulbs Direct

Norman is correct – the transformer in the fireplace is not designed to work with LED’s – many transformers need a minimum load to work, such as 50W, which is fine when you have two 28W halogen light bulbs installed. But when you replace with LED, the light bulbs may be only 2W or 3W and this is not enough to work with the transformer. You could contact an electrician and see if they could replace the transformer that is in the fireplace. We sell a LED driver that could be installed instead.
Alternatively – stock up on GU4 MR11 light bulbs while you can – these light bulbs have now been banned for import into the UK/EU, but retailers can continue to sell any stock they currently have.