12V G4 bulbs

A G4 12V LED bulb is a small low-voltage bulb whose base consists of two pins 4 mm apart, hence its name. It fits compact light fixtures: recessed spotlights, multi-point pendant lights, cabinet or display case lighting. It works with a transformer that steps down the 230V mains supply to 12V.

What is a G4 12V LED bulb and which light fixtures is it found in?

A G4 12V LED bulb is a small low-voltage bulb whose base consists of two pins 4 mm apart, hence its name. It fits compact light fixtures: recessed spotlights, multi-point pendant lights, cabinet or display case lighting. It works with a transformer that steps down the 230V mains supply to 12V.

A G4 12V LED bulb, a two-pin base

The G4 base is recognisable by its two thin pins that are pushed into the socket, with no screw or bayonet fitting. The bulb is short, often just a module placed in a reflector or a cup. In a recessed ceiling spotlight, it almost disappears: what matters is the halo it leaves on the wall or worktop. The choice therefore comes down to colour temperature and available space, before any technical debate. Find the models in our 12V low-voltage bulbs.

Why 12 volts and not 230 volts?

12V allows a tiny bulb to be housed in a very slim light fixture, without the insulation constraints of the mains supply. The transformer, built into the spotlight, the track or housed separately in a box, performs the conversion. It is the transformer that determines operation: its minimum load and its type decide whether a modern bulb will light correctly. To equip an entire room, start from the light fixture and work back to the bulb, browsing the Designix lighting catalogue.

How do I know which bulb I need?

First locate the base and voltage marked on the old bulb or on the socket: a G4 is not screwed in, it is pinned, and it only accepts 12V. Then check the available space, the desired light colour and, if the fixture is on a dimmer, the bulb's compatibility.

Read the base and voltage on the socket

Remove the bulb in place and read what is engraved on the socket or base. If you read GU5.3, the pins are thicker and the bulb often wider: look at our GU5.3 bulbs for 12V spotlights. If the marking says 230V, there is no transformer and you need to look elsewhere, in the full range of bulbs for all bases or towards other G4 and G9 bases. A small accent light may also require an E14 base for small light fixtures.

Measure the clearance before ordering

A G4 fits into a very short space. Measure the usable depth between the socket and the edge of the fixture, then the free diameter around the module. A bulb that is too long prevents the protective glass or reflector from being put back. Also note the current colour temperature: two bulbs of different colours in the same room are immediately noticeable.

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

Yes, provided you stay at 12V and on a G4 base. A G4 LED runs cooler and uses less power than halogen, but some older transformers require a minimum load: if the fixture does not light or flickers, check the transformer before drawing conclusions.

What really changes with a G4 LED

The fixture heats up much less, which matters in a niche or under a shelf where air circulation is poor. The light remains stable over time and consumption drops for a comparable light level. The result depends on the module: a quality module gives a uniform colour, a very cheap model may lean green or flicker. Compare in our 12V LED bulbs.

Transformer and dimmer, the two points to check

An electronic transformer designed for halogen may not start with an LED that draws too little: it expects a minimum load. The classic symptom is flickering or delayed start-up. If the fixture is on a dimmer, check that the bulb is declared compatible and that the dimmer accepts the low load, for example among our dimmable LED bulbs. Otherwise, test one bulb before replacing the whole setup.

G4 12V 10W or 20W bulb: how do I read the power rating?

The figures 10W and 20W correspond to the original consumption, often halogen. In LED, the stated power is much lower for a comparable output. The useful reference is therefore not the watt but the luminous flux in lumens, to compare with the bulb you are replacing, so as to keep the same light level. General guide: a 12W LED gives around 1000 to 1200 lm, and a 3W G4 LED can replace a 25W halogen.

Halogen and LED cannot be compared by wattage

With a halogen, 20W visibly lights more than 10W, and heats up more. With an LED, the same nominal power says almost nothing about the light level produced. Continuing to think in watts leads to buying too weak or too strong, and to wondering why the room is less bright than before. Instead, identify the fixture's technology: if it is 230V, GU10 230V bulbs or 220V LED bulbs are the right families.

Luminous flux in lumens, the only reliable reference

Flux, expressed in lumens, indicates the amount of light emitted. This is the value to compare from one bulb to another, staying with an equivalent use: a hallway needs little, a worktop needs more. Power in watts mainly serves to check what the transformer can supply, information found in its instructions.

Which bulb lights best: warm white, neutral white or cool white?

No colour temperature lights better than another: each creates an atmosphere. Warm white, around 2700K, suits the living room and bedroom; neutral white, between 3000 and 4000K, suits kitchens, bathrooms and worktops. For the same bulb, it is the luminous flux in lumens that determines the amount of light, not the colour temperature.

2700K and 3000K, the light that relaxes

Around 2700K, the light leans golden and extends the evening without straining the eye. This is the colour of our 2700K warm white bulbs, suited to a reading corner or a pendant above a table. At 3000K, the white remains soft but a little crisper, close to the halogen rendering: see the 3000K colour for the kitchen and hallways.

4000K and above, the light that works

Above 4000K, the white becomes clear, with no yellow cast. This suits bathrooms, worktops and areas where colours or details are distinguished. In a living room, this colour cools the atmosphere in the evening. One rule holds: keep the same colour temperature on all light points in the same room.

Where to install a G4 12V LED bulb in the home?

A G4 12V finds its place where the light fixture is small: recessed spotlights, under-cabinet track, display case, niche, multi-arm pendant. In a bathroom or a sheltered outdoor area, check the fixture's ingress protection rating, because the bulb alone does not protect against moisture.

Bathroom and damp rooms, check the fixture's IP rating

The ingress protection rating, marked IP followed by two digits, qualifies the fixture, not the bulb. A spotlight above a bathtub or in the splash zone must be protected against splashes. The G4 bulb remains a bare bulb: it is the protective glass and the fixture's seals that do the work. The location decides the rest, not the bulb's specification.

Display cases, furniture and worktops

Under a shelf or in a display case, the G4 lights up close without taking up space. Choose a colour temperature consistent with the room: for a rest area, look at our living room bulbs or bedroom lighting, then carry that colour over to the furniture spotlights. To harmonise several rooms, browse all our light fixtures by room.

How do I wire 3 bulbs in parallel?

Three G4 bulbs are wired in parallel: each socket receives the two circuit wires, with the same markings on each. The voltage remains identical across all three, which is not the case in series. The transformer must be able to supply the whole setup and the connection is always made with the power off.

The parallel diagram, socket by socket

The principle is simple to describe: the two circuit wires arrive at the first socket, continue to the second, then to the third, with the same marking on each socket. Each bulb therefore receives the full transformer voltage. In series, a faulty bulb would switch off the others and the voltage would be shared, which is not the setup expected on a domestic light fixture.

What must stay in an electrician's hands

Switch off the power at the consumer unit before any work. Transformer sizing, wire cross-section and connection to an existing circuit are found in the fixture's instructions and in installation rules: these points cannot be improvised. If the fixture is a complete multi-arm model, follow the original wiring, for example on our multi-point 12V spotlight models.

How to change and maintain a G4 12V LED bulb?

Switch off the power before unplugging the bulb: on a G4 base, it is removed by pulling it straight out, without twisting. A dry cloth is enough for the fixture, and it is better not to touch the LED module with your fingers. Replacement is done cold, once the bulb has cooled.

Unplug without forcing

The two pins are thin: a sideways movement twists them and damages the socket. Hold the bulb by its edges, pull along the axis. If it resists, it is often because the holder is seized by heat, not because the bulb is stuck. A dry brush or a lint-free cloth removes dust from the reflector, which otherwise swallows part of the light.

Making a G4 LED last

An LED heats up less, but it does not like being enclosed without ventilation: let closed fixtures breathe and do not block the vents. Avoid violent voltage fluctuations and undersized transformers. To change style in classic fixtures, compare our modern bulbs and filament bulbs, keeping the same base and voltage.

One last point before confirming: note the base, voltage and colour temperature in a photo of the old bulb, and you will order the right reference first time. At Designix, payment is secure, delivery is tracked and returns are possible, with customer service available to check transformer or dimmer compatibility.

Frequently asked questions