What Wire to Use for Under Cabinet Lighting: A 7-Step Checklist

Who this is for: If you're installing hardwired or low-voltage under cabinet lights in a commercial kitchen, retail display, or office pantry, this checklist is for you. It is not for temporary event décor. If you're pricing a spotlight rental for a trade show booth, call the rental company and move on. This is about wire that gets buried in walls and inspected.

In my role coordinating lighting and electrical product orders for contractors, I've handled more than 200 rush replacements. The most common panic call sounds like this: 'We're in the middle of a kitchen remodel and the lighting wire is wrong.' The fix isn't complicated, but it has to happen before the drywall goes up. This is the checklist I use every time.

The 7-Step Wire Checklist for Under Cabinet Lighting

Step 1: Identify line voltage vs. low voltage

Before you buy anything, find the voltage requirement on the fixture label. An Eaton under cabinet LED fixture, for example, is usually marked either 120V input or 24V DC with a separate driver. I've seen a job where a client said 'low voltage' and I assumed 12V. They had 24V drivers. Everything lit up for a second, then died. That's an expensive way to learn the difference.

Checkpoint: Write down the input voltage and the driver output voltage before you buy wire.

Step 2: For line-voltage lights, choose 14/2 or 12/2 NM cable

If your under cabinet light is hardwired to a 120V switch, you're dealing with line voltage. On a 15-amp lighting circuit, 14 AWG wire is the standard. On a 20-amp circuit, use 12 AWG. A 15-amp lighting circuit is common in a lot of residential and light-commercial work, so 14/2 with ground is usually the no-brainer choice.

Use NM cable, often called Romex, in walls and other dry locations. For branch circuits, the ampacity rules come from the National Electrical Code. If you're replacing an existing fixture and the breaker is 15A, 14/2 is almost always safe. If you're adding new lighting to a 20A kitchen circuit, step up to 12/2.

Step 3: For low-voltage lights, use 18/2 or 16/2 CL2 wire

Low-voltage under cabinet lighting, typically 12V or 24V, doesn't need 12/2 NM cable. It needs power-limited circuit wire rated CL2 or CL3. For short runs, 18/2 is fine. For anything over about 15 feet, 16/2 cuts down voltage drop and keeps the brightness even from one end to the other.

Don't use speaker wire. It doesn't have the same insulation rating and it almost always fails inspection. If the cable jacket doesn't print CL2 or CL3, that's a red flag. Per NEC Article 725, Class 2 circuits can use CL2 wire; line-voltage branch circuits are covered under separate wiring methods.

Step 4: Size the power supply to the connected load

Now the math part. Add up the wattage of all fixtures, then add about 25% buffer. Say you have six 8W under cabinet fixtures. 6 × 8 = 48W. A 60W-rated power supply gives you enough headroom.

For an Eaton power supply or LED driver, check the Class 2 rating on the label. Class 2 outputs are allowed to use CL2 wire. If the output is not Class 2, stop and re-read the spec sheet. You might need a different cable and an electrician.

I once had a job where the numbers said 18/2 would work over a 25-foot run, and my gut said step up to 16/2. I went with gut. Turns out the fixture's push-in terminals were rated for 18 AWG only, so the 16/2 wouldn't fit. The real lesson: check the connector specs, not just voltage drop.

Step 5: Put the switch or sensor where you can actually reach it

Under cabinet lighting is installed low, but the switch should not be hidden behind a coffee machine. In many kitchens, the easiest place for the switch is above the counter, near the cabinet. If you're retrofitting with an Eaton occupancy sensor or dimmer, confirm the sensor is compatible with LED loads before you buy.

This is also the point where I remind electricians to add a service disconnect. Some inspectors require a way to disconnect the luminaire for maintenance. A switch in an accessible location usually satisfies that.

Step 6: Ask about emergency lighting and battery backup

This is the step most people skip, especially in commercial kitchens. If your under cabinet lights are part of the egress path, you may need them to stay on during a power loss. That's where an Eaton battery backup unit or emergency lighting inverter comes in.

Don't use a consumer computer UPS for an emergency lighting circuit. Eaton makes both UPS systems and emergency lighting battery packs. If a fixture is required to stay on during an outage, it needs a listed emergency battery pack, not a desktop UPS.

Bottom line: if the building inspector asks why your disconnect is a pull-out battery, that conversation won't go well.

Step 7: Test every connection before you close up the wall

No matter how confident you are in the wire selection, test the circuit at the last fixture. Check voltage under load. Check polarity on low-voltage DC. Then turn it on and let it run for at least a minute before the drywall goes on.

I've seen communication breakdowns cause the worst delays. The electrician said 'the driver is at the cabinet,' and the lighting supplier heard 'the driver is in the cabinet above the microwave.' Those two things are not the same. The result was a 30-minute install quote turning into a three-hour demo and rewire.

Common Mistakes to Avoid

• Using 12/2 NM for low-voltage LED tape. It's the wrong cable. You need CL2-rated low-voltage wire, not line-voltage cable.
• Using 18/2 wire for line-voltage power. 18 AWG isn't rated for a 120V branch circuit. This is a code violation and a fire risk.
• Oversizing the wire without checking the fixture terminals. Practice step 4 before finalizing the wire gauge.
• Forgetting the warranty paperwork. If you buy an Eaton power supply, keep the label and the serial number. Replacement is much easier when you know the exact model.

When This Checklist Doesn't Apply

If you're looking for temporary accent lighting, a spotlight rental from an event lighting vendor is a different process. You're not choosing wire; you're choosing beam spread and wattage. Similarly, if your search was about a warranty plan's Asurion spotlight on appliance coverage, keep one thing in mind: a warranty covers repairs, not wire selection. The wire for under cabinet lighting is based on the fixture's voltage, the circuit size, and local code. Not your service plan.

So, What Wire Actually Works?

For most residential and light-commercial under cabinet lighting jobs:

• Line-voltage, hardwired: 14/2 NM on a 15A circuit, or 12/2 NM on a 20A circuit.
• Low-voltage LED, short run: 18/2 CL2 wire.
• Low-voltage LED, long run: 16/2 CL2 wire in most cases, but verify terminal ratings.

Use the fixture's labeled voltage and the driver's Class 2 rating as your guide. If you're in the U.S., follow the NEC and your local amendments. When in doubt, bring an electrician in before the drywall, not after.