LED Strip Voltage Drop Explained: 12V vs 24V, Run Length and Power Injection

LED strip voltage drop is the reason a long run looks bright at the feed and tired at the far end. The copper traces inside the strip and the wire that feeds it both have a little resistance. Push current through that resistance and you lose voltage along the way. LEDs are sensitive to it: a few percent less voltage means visibly less light, and on some strips a warmer or greener tint as well.

The good news is that it's predictable. Once you know the numbers, you can design it out before anything is installed.

Why 24V Beats 12V on Longer Runs

For the same load, current equals power divided by voltage:

• a 60 W run at 12V draws 5 A;
• the same run at 24V draws 2.5 A.

Voltage drop in a conductor is current × resistance, so halving the current halves the drop. The power wasted as heat in the wire is current² × resistance, so that falls to a quarter. That's the whole case for 24V, and it's why the published maximum run of a 24V strip is usually longer than its 12V twin.

What "Maximum Run" Really Means

Every strip has a published maximum single-feed run: the longest length you can power from one end while keeping the brightness difference end to end within an acceptable limit. It depends on the strip's watts per foot and on how much copper is in its circuit board. As a rule of thumb, a standard 24V strip runs about 16 ft from one feed. High-power strips run shorter.

Treat that figure as a ceiling, not a target. A run designed to exactly its maximum has no margin left for the lead wire, the connectors or real-world tolerances. The maximum run length guide explains how manufacturers set the number.

Three Ways to Handle a Long Run

1. Feed from both ends or the middle

Feeding a run from both ends, or from the middle, halves the distance each feed has to cover. The driver still supplies the same total wattage, but the drop along any one path is much smaller.

2. Split it into shorter runs

Break the run into segments and give each one its own home run back to the driver. It's the cleanest fix when the layout already has natural breaks, like separate cabinets, bays or walls.

3. Use a strip built for distance

Some strips use circuitry that holds brightness over much longer runs from a single feed. ENKORA's LONG RUN series covers single-feed runs from about 49 ft to 98 ft, depending on the build. On perimeters, corridors and facades that can save several extra feeds, and every feed you don't need is one less penetration and junction box.

Don't Forget the Feed Wire

The wire between driver and strip drops voltage too, and it's often worse than installers expect because drivers end up mounted a long way from the fixture. You can estimate it like this:

Voltage drop = 2 × one-way length (ft) × current (A) × resistance (Ω per 1,000 ft) ÷ 1,000

The factor of 2 accounts for the positive and the negative conductor. Approximate copper resistance at room temperature:

A Worked Example

Say you're lighting a 40 ft cove with a 24V strip rated at 3 W/ft and a published maximum run of 16.4 ft. The driver sits in a mechanical closet 30 ft away.

1. Total load: 40 ft × 3 W/ft = 120 W.
2. Driver size: 120 W ÷ 0.8 = 150 W minimum.
3. Runs: 40 ft is well past 16.4 ft, so split it. Three runs of about 13.3 ft each sit comfortably under the limit.
4. Current per run: 13.3 ft × 3 W/ft ≈ 40 W, and 40 W ÷ 24 V ≈ 1.7 A.
5. Feed wire drop per run on 18 AWG: 2 × 30 × 1.7 × 6.4 ÷ 1,000 ≈ 0.65 V, or about 2.7% of 24V. That's before the strip loses anything of its own.
6. On 14 AWG: 2 × 30 × 1.7 × 2.5 ÷ 1,000 ≈ 0.26 V, about 1%.

In this case the upgrade to 14 AWG is cheap insurance. A common design target is to keep the total drop, wire plus strip, to a few percent.

Size the Driver Separately

Voltage drop and driver size are different problems. You can size a driver generously and still get a run that sags at the end. Size the driver for the total load with 20% headroom, then check each run against its maximum length and its feed wire. The power supply calculator does both for a chosen ENKORA strip, and powering LED strips covers the rest.