COB LED Strip Power Consumption: What Size Driver Do You Actually Need?

Under-power a COB run and it dims toward the end; over-size blindly and you waste money on a driver you don't need. The good news is COB driver sizing is simple arithmetic once you know the real watts-per-metre figure. I'll walk through it with worked examples so you can size any run with confidence.

Start with watts per metre

Every strip has a rated power draw, printed on the listing or the PCB — for COB this commonly ranges from about 8–10 W/m on low-density up to 18–25 W/m on high-density 24V reels. Always use the actual figure for your exact model, not a guess based on appearance.

Total strip watts = watts per metre × total metres. That's the raw load before any safety margin.

Add the 20–25% safety margin

You don't run a driver flat out. Continuous full load shortens its life and runs it hot. Size the driver so the load is about 80% of its rated output:

Driver size = total strip watts ÷ 0.8

Worked example: a 14 W/m COB strip, 8 metres. Total = 112W. Driver = 112 ÷ 0.8 = 140W — so you'd fit a 150W 24V driver (the nearest standard size up).

Why 24V makes long runs easier

For the same power, 24V draws half the current of 12V (power = voltage × current). Lower current means less voltage drop along the PCB, so the far end of a long run stays the same brightness and you inject power less often. For runs over about 5 metres I default to 24V COB. The maximum single-feed length depends on the strip's trace and wattage — check the spec, but as a rule inject additional power roughly every 8–10 metres on high-density 24V COB.

Multiple drivers vs power injection

On a long run you have two clean options: either one driver with power-injection wires feeding the strip at several points, or split the run into sections each on its own driver. For a single room, injection is tidy; across a large commercial space, separate drivers per zone are easier to control and isolate if something fails. Don't just daisy-chain strip beyond its rated feed length and hope — that's how you get a visibly dim tail end.

Don't forget the control side

If you're dimming, the dimmer or controller must also handle the total current/wattage and sit between driver and strip (or on the mains side, depending on type). An overloaded dimmer causes flickering — the flicker troubleshooting guide covers that. Wire gauge on longer feed runs matters too; see the wiring and fuse guide.

FAQ

What happens if my driver is too small?

It runs overloaded and hot, may shut down intermittently or fail early, and the strip can dim or flicker. Always size above the calculated load, not at it.

Can I use one big driver for several separate rooms?

Yes electrically, but separate drivers per zone give independent control and make faults easier to isolate. For simple single-circuit installs one driver is fine.

Does dimming reduce the watts the driver draws?

The light output and power to the strip drop as you dim, but you still size the driver for the strip's full undimmed load, since that's its worst case.

Send me the COB model number and total metres (plus your run layout) and I'll calculate the driver wattage, number of feeds, and wire gauge — matched to a strip from the COB range.