G4 LED Bulbs

G4 LED bulbs are the small two-pin capsules found in cooker hoods, display cabinets, under-cabinet strips, crystal chandeliers, bathroom mirror lights and plenty of older halogen fittings. They're easy to overlook until one goes, and then the question is always the same: which replacement will fit, light up properly and not flicker. This page covers that, so you can buy the right G4 bulb first time.

Every G4 bulb we sell is LED. Compared with the halogen capsules these fittings were designed for, an LED G4 uses around a tenth of the power, runs far cooler and lasts tens of thousands of hours rather than one or two thousand. That matters most in places that are awkward to reach, like a hood above the hob or a glass cabinet with the bulb tucked behind a shelf.

What is a G4 bulb?

The name describes the base. "G" means a bi-pin fitting, and "4" is the distance between the two pins in millimetres. The pins are thin and straight, and the bulb simply pushes into the socket with no twisting. G4 is one of the smallest common lamp bases, which is why it turns up in compact fittings where a GU10 or E14 bulb would never fit.

Most G4 bulbs run at low voltage, normally 12V, so the fitting they go into has a transformer or driver somewhere in the circuit that steps mains power down. That is the single most important thing to understand before you replace one, and it's covered in more detail below.

G4, G9 and GY6.35: what's the difference?

These three get mixed up all the time because the bulbs look alike at a glance.

• G4 has two straight pins 4mm apart and usually runs on 12V.
• G9 has two looped pins 9mm apart and runs directly on mains voltage (230V). See our G9 LED bulbs if your old bulb has curled pins.
• GY6.35 (sometimes sold as G6.35) has straight pins 6.35mm apart, also usually 12V, and is often found in slightly bigger fittings.

A G4 bulb will not go into a G9 or GY6.35 socket, and you should never try to force it. The quickest check is to look at the old bulb: straight, close-set pins with a gap you could just fit a pencil lead into is almost always G4. If the bulb has markings, the base type is usually printed on the glass or on the metal at the base.

Will an LED G4 bulb work with my existing transformer?

Usually, but not always, and this is where most problems come from. Many halogen fittings use an electronic transformer that needs a minimum load to work properly, often 10W, 20W or more. A 20W halogen capsule meets that easily. A 2W LED does not, so the transformer may not "see" it, and the result can be flickering, buzzing, the bulb switching on and off, or nothing at all.

A few practical points help here:

• Check the transformer label. If it shows a minimum load and your new LED bulbs add up to less than that, swap the transformer for a 12V LED driver rated for the total wattage.
• Where several G4 bulbs share one transformer, as in a chandelier or a run of cabinet lights, the combined wattage can sometimes be enough to keep an electronic transformer happy.
• Older magnetic (wire-wound) transformers often work with LEDs, but they need AC-compatible bulbs. Most modern LED G4 bulbs are marked 12V AC/DC, which covers both.
• If you're unsure, replace one bulb first and run it for a while before buying for the whole fitting.

Changing a transformer or driver is a job for a qualified electrician. Swapping the bulb itself is fine to do yourself once the fitting is switched off and cool.

How bright is a 2W G4 LED bulb?

A 2W LED G4 giving around 200 lumens is roughly the same brightness as a 20W halogen capsule, which is the most common size these fittings were built for. For smaller 10W halogen capsules, a 1W LED is a closer match, and for 35W capsules you'd look for something nearer 3W to 4W. When comparing bulbs, go by lumens rather than watts, because lumens tell you how much light you actually get.

Which colour temperature should I choose?

For most homes, warm white (around 2700K to 3000K) is the safe choice. It's close to the colour of the halogen bulb you're replacing, so a cabinet or chandelier will look the same as it did before. Warm white suits living rooms, display cabinets, crystal chandeliers and bedside fittings.

Cooler white (around 4000K) can work well in a cooker hood or a kitchen under-cabinet light where you want a crisper look for food preparation. Whatever you pick, use the same colour temperature for every bulb in one fitting, because mixing them is very noticeable in a multi-light chandelier.

Are G4 LED bulbs dimmable?

Most G4 LED bulbs are not dimmable, and that includes the Endon warm white pack we currently stock. Dimming a low-voltage circuit depends on the bulb, the transformer or driver and the dimmer switch all being compatible with each other, so it's not as simple as fitting a dimmable bulb. If your G4 fitting is on a dimmer now, either replace the dimmer with a standard switch or speak to an electrician about a compatible dimmable driver before buying.

Will an LED G4 bulb fit where my halogen bulb was?

Check the size before you order. Halogen G4 capsules are tiny, and while LED versions have shrunk a lot, some are still a little longer or wider. That's rarely an issue in an open chandelier but can matter in a cooker hood or a sealed cabinet light where the bulb sits behind a small glass cover. Measure the space from the socket to the cover and compare it with the bulb dimensions on the product page.

Where G4 bulbs are used

• Cooker and extractor hoods
• Glass display cabinets and shelf lights
• Under-cabinet kitchen lights
• Crystal chandeliers and multi-arm ceiling fittings
• Bathroom mirror and cabinet lights
• Small reading, desk and bedside lamps
• Caravans, boats and other 12V setups

Other bulb types

If your fitting turns out to use a different base, have a look through our full range of LED bulbs. For spotlights and downlights you'll most likely need GU10 LED bulbs. Small candle and golf ball bulbs for wall lights and chandeliers are in E14 LED bulbs, while standard ceiling pendants and table lamps take E27 or B22 bulbs. For exposed fittings where the bulb is part of the look, browse our decorative bulbs.

All G4 LED bulbs ship with fast delivery across Ireland and Europe. If you're not sure which bulb your fitting needs, send us a photo of the old bulb and the label on the fitting or transformer, and we'll help you pick the right one.