How Many Amps Does a 4 Foot LED Light Draw?

2026-03-14News LED Light FAQ 310

People usually ask how many amps does a 4 foot led light draw when they are planning a workshop upgrade, garage lighting, or warehouse installation.

The question often comes up when someone is staring at the breaker panel.

“How many lights can this circuit handle?”

It’s a fair question. But the answer isn’t always a single number because 4-foot LED lights come in several wattage levels.

Still, the current draw is almost always low compared with older fluorescent fixtures.

Start with the Basic Electrical Formula

Electricians normally calculate current using the relationship defined by Ohm’s Law.

The formula looks like this:

Amps = Watts ÷ Volts

Most 4 foot LED lights use between 18W and 40W, depending on brightness and design.

So let’s look at a few realistic examples.

18W 4-foot LED tube at 120V

18 ÷ 120 = 0.15 amps

25W 4-foot LED shop light

25 ÷ 120 ≈ 0.21 amps

40W high-output 4ft LED fixture

40 ÷ 120 ≈ 0.33 amps

So in most cases, a 4 foot LED light draws somewhere between 0.15 and 0.35 amps.

That’s a tiny load compared with traditional lighting.

What Happens When You Measure It in the Field

Theory is helpful, but real installations always show small variations.

A while back we upgraded the lighting in a small mechanical workshop. The old fluorescent fixtures were replaced with modern LED shop lights. Each one was rated at 40 watts.

On paper, that meant about 0.33 amps per fixture.

When we measured with a clamp meter, most lights were pulling 0.35 amps.

Close, but not identical.

The difference came from the LED driver. Drivers convert AC power into the stable current needed for the LED chips. During that process a small amount of energy is lost, and the power factor slightly changes the measured current.

Nothing unusual — just real electrical behavior.

Why LED Shop Lights Use So Little Current

LED technology is dramatically more efficient than the fluorescent fixtures many buildings still use.

Fluorescent lamps rely on ballasts and gas discharge tubes. A lot of energy turns into heat.

LED systems avoid most of that waste.

According to research from the U.S. Department of Energy, LED lighting can reduce electricity consumption by 50–75% compared with conventional lighting technologies. That efficiency is exactly why the amp draw stays so low.

Even a bright 4 foot LED shop light rarely draws more than a third of an amp.

How Many 4-Foot LED Lights Can Run on One Circuit?

Now we get to the real reason people ask how many amps does a 4 foot led light draw.

They want to know how many lights can run on a circuit.

Let’s assume a 15-amp breaker, which is common in garages and workshops.

If each fixture draws 0.3 amps, the circuit could theoretically run around 50 lights.

But electricians don’t design systems that aggressively.

Groups like the National Electrical Manufacturers Association recommend keeping circuit loads well below maximum capacity for safety and reliability.

In practice, installers usually run far fewer fixtures per circuit.

Still — the electrical demand is extremely manageable.

What We See in Real Lighting Projects

At SEEKINGLED, customers often replace long rows of fluorescent shop lights with LED fixtures.

The concern before the upgrade is always similar.

“Will we need more circuits?”

Almost never.

When the new LED Flood Light switch on, the total electrical load usually drops significantly. Buildings that once ran dozens of fluorescent tubes suddenly consume far less power.

The lighting becomes brighter, the maintenance drops, and the circuit load becomes easier to manage.

That’s why LED shop lights have taken over workshops, garages, and warehouses so quickly.

A Quick Rule Installers Use

When electricians estimate lighting loads quickly, they often use simple guidelines.

For 4 foot LED lights:

18–20W LED tube → about 0.15 amps
25–30W shop light → about 0.20–0.25 amps
40W high-output fixture → about 0.30–0.35 amps

These numbers are reliable enough for planning circuits and wiring layouts.

Actual measurements usually land very close.