Which LED driver do I need? 12V or 24V, wattage, IP rating and constant current explained

LED strip, under-cabinet lights, cabinet spots and most low-voltage fittings do not plug into the mains. They need a driver – a power supply that turns 230 V AC into the low-voltage DC the LEDs run on. Buy the wrong one and the lights flicker, run dim, or the driver overheats. The right one is easy to pick once you know four things: the voltage, the wattage, where it will live, and whether your light wants constant voltage or constant current.

1. Match the voltage: 12 V, 24 V or 5 V

Your light fitting or LED strip states its voltage. A 12 V strip needs a 12 V driver; a 24 V strip needs a 24 V driver. There is no mixing. As a rule, 12 V is the common choice for shorter runs and most fittings; 24 V suits longer strip runs, because the lower current means less voltage drop and less dimming toward the far end. 5 V is for addressable pixel strip and similar electronics. This range has all three: 12 V, 24 V and 5 V enclosed supplies.

2. Size the wattage: the 20–25% rule

Add up the wattage of everything the driver will power, then choose a driver about 20–25% above that total. For example, 75–80 W of LED strip wants a 100 W driver. Running a driver at its limit shortens its life; the headroom keeps it cool. If you are powering strip, the strip’s listing gives watts per metre – multiply by the length.

3. Where will it live? IP ratings

The IP rating tells you how well the case keeps out dust and water. In this range:

• IP20 – indoor, dry. Inside a cabinet, a ceiling void or an enclosure. The 12 V enclosed supply (12 W to 600 W, aluminium, screw terminals) and the 12 V slim IP20 driver (15 W to 360 W, fanless) are the workhorses here.
• IP44 – splash resistant. A bathroom cabinet or a kitchen plinth where it may get splashed but not soaked: the 12 V IP44 driver, 7 W to 60 W.
• IP45 – rainproof. Under a canopy or in a porch: the 12 V IP45 supply, 60 W to 400 W.
• IP67 – waterproof. Garden lighting, outdoor strip, anywhere it can get properly wet: the 12 V IP67 driver (10 W to 350 W) and 24 V IP67 driver (10 W to 200 W), both sealed aluminium, or the ultra slim IP67 where depth is tight.

4. Constant voltage or constant current?

Almost everything above is constant voltage: the driver holds 12 V or 24 V and the lights draw what they need. That is what LED strip, under-cabinet bars and most 12 V fittings want.

Some downlights and panel lights instead want a constant current driver, which holds a fixed current – 280 mA, 300 mA, 600 mA, 1000 mA – and lets the voltage float. The fitting will say so, with its current in mA. Match the current exactly, then choose the wattage band. Here that means the 280 mA driver (3 W to 24 W), the 300 mA to 1000 mA driver (3 W to 50 W), or the sealed IP67 constant current driver for outdoor fittings.

Enclosed, compact or slim?

• Enclosed metal supplies (screw terminals, open ends) are for installing inside an enclosure or cabinet, where nothing can touch the terminals. They give the widest wattage range and the lowest cost per watt.
• Compact plastic drivers like the 12 V compact (18 W to 100 W, flame-retardant ABS) are for small indoor jobs where a metal box is overkill.
• Slim drivers like the slim aluminium IP20 are for ceiling voids, plinths and behind panels where height is the constraint.

Dimming

A standard driver is not dimmable, and putting it on a dimmer switch damages it. Where a listing says “Dimmable: no”, that is what it means. If you need dimming, buy a driver sold as dimmable and match it to the dimmer type.

Safety

These are mains-connected devices. Electrical work should be done by a competent person, and an enclosed supply must be installed where its terminals cannot be touched.

What to buy

• 12 V IP20 enclosed supply, 12 W to 600 W – indoor, the widest range
• 24 V IP20 enclosed supply, 24 W to 360 W – for 24 V strip and longer runs
• 12 V slim IP20 driver, 15 W to 360 W – fanless, for tight spaces
• 12 V IP67 waterproof driver and 24 V IP67 – outdoors
• Constant current driver, 300–1000 mA – for fittings that specify a current
• Browse all cables and LED drivers

Frequently asked questions

Can I run 24 V strip from a 12 V driver? No. It will be dim or not light at all. The voltages must match.

Can a driver be too big? A constant voltage driver with more wattage than you need is fine – the lights only draw what they use. Too small is the problem.

Can I put an IP20 supply in a garage? Only inside a dry enclosure. For anything damp, go to IP44 or above; for outdoors, IP67.

What does “switching” power supply mean? It is the standard efficient design used for LED supplies – nothing to choose between here.