What is the difference between GU10 and GU5.3?

GU10 runs on 230 volts and needs no transformer. GU5.3 runs on 12 volts and always needs one. You tell them apart by the pins: GU10 has two thick ones with a knob on the end, GU5.3 two thin straight ones. They do not fit each other's holder.

The numbers give it away

On both sockets the number stands for the distance between the pins in millimeters. On GU10 that is 10 mm, on GU5.3 exactly 5.3 mm. The U refers to the type of contact.

The shape differs too: on GU10 there is a thickened end on each pin, which is why you turn the lamp a quarter turn to lock it. A GU5.3 you push straight in and pull straight out.

The real difference is the voltage

That single difference determines almost everything. With GU10 the mains voltage runs all the way into the lamp and all the electronics sit in the lamp base. With GU5.3 there is a separate box above your ceiling converting 230 to 12 volts, and that box is the part that causes trouble most often.

Why GU5.3 has fallen out of favor

In the halogen era 12 volts had advantages: smaller lamps, better beams. With LED those advantages have gone and the drawbacks have stayed.

You notice the biggest drawback when switching over. An old halogen transformer needs a minimum load, often 20 watts or more. Replace four 35-watt halogen spots with 5-watt LEDs and the load drops from 140 to 20 watts, so the transformer starts switching irregularly. That shows up as flicker.

What we carry

Almost everything we sell is GU10 or integrated LED. Four recessed spotlights take either, and they say so:

• Plano — GU10 or MR16, Ø80 mm, €9.95
• Privo — GU10 or MR16, Ø68 mm, IP65, €11.95
• Luma — GU10 or MR16, Ø72 mm, €12.95
• Feno — GU10 or MR16, Ø80 mm, €10.95

With those four you choose. Our advice is almost always GU10, unless there is a working 12V installation already in place that you do not want to change.

If you do stay on 12 volts

Then replace the halogen transformer with an LED driver matched to the number of spots. Our 20-watt 12V driver feeds a maximum of six spots, the 40-watt version a maximum of ten. Both dimmable with a remote control.

Bear in mind that at 12 volts you also have to watch cable length: over a long thin wire the voltage drops and the spots at the end become visibly weaker. At 230 volts that does not come into play in a home.

What about safety?

Twelve volts sounds safer than 230, and in the lamp itself it is. But that does not mean a 12V installation asks for less care: the transformer hangs off mains voltage, and the current in the 12V cables is actually higher, because the same power at a lower voltage means more amps. Cables that are too thin get warm as a result.

In practice a properly executed 230V installation with GU10 is therefore no less safe, and it has considerably fewer parts that can fail. That is the third reason new builds and renovations are laid out on 230 volts as standard these days.

Can you swap them?

No. Adapters from GU5.3 to GU10 exist, but they make the lamp longer and do nothing about the voltage difference — a GU10 lamp on 12 volts simply will not light. If you are stuck, choose a fixture that takes both.

More about the socket itself in What is a GU10 socket?, and switching over is covered in How do you replace halogen spots with LED? The range is in the recessed spotlights.