Can I replace a halogen G4 bulb with an LED G4 bulb?

Yes you can replace a halogen G4 bulb with a LED version.  There are a few different factors that you will need to consider before doing so but in the vast majority of cases it should be as simple as swapping the two bulbs over.   

Driver/transformer compatibility

The first thing you will need to check is the voltage.  Most G4 bulbs operate on 12V and LED G4 bulbs have been manufactured with this in mind.  The majority of transformers used in a lighting circuit for G4 bulbs will be 12V.  It is essential however to confirm that the transformer is 12V as well as the replacement bulb before you install it.  If the voltage is different then you should look for a bulb that has the same voltage as the transformer. 

You should also check the advised wattage load of the transformer as LED bulbs will often use less wattage than a halogen bulb.  A halogen transformer will have a minimum amount of wattage which will be advised on the driver or you can find this out by searching the part number for the driver online or by contacting a light bulb retailer such as ourselves.  If the LED bulb does not match the minimum advised wattage it can cause the bulb to flicker or buzz or not work at all.  If this is happening when you connect a LED G4 bulb we would recommend purchasing an appropriate LED driver.  If you are purchasing a new LED driver for your bulb and you are looking to use the bulb with a dimmer switch you will need to make sure that both the bulb and the driver are dimmable compatible.

Physical Dimensions

It is also worthwhile checking the length and the width of the body of the bulb.  This is especially important if the bulb you had previously fits snugly within your lighting fixture.  G4 bulbs will always have the same length between the pins as this is what the term G4 means so you do not need to worry about this dimension being different.  LED G4 bulbs however can be slightly longer due to them needing more internal components than halogen G4 bulbs.

Light Output - A.K.A Lumens

It is also worth considering the light output you need.  If you are looking to have the same amount of brightness as your previous bulb you will need to compare lumens rather than wattage.  This is because LED bulbs use a lower amount of wattage than halogen bulbs to produce the same amount of light.  A 20W halogen bulb for example has 200-300 lumens and the LED equivalent of this that would have a similar amount of lumens would be a 2-3W LED G4 bulb.