Built-in microwaves can be removed and replaced by a homeowner with basic tools, but the job involves electrical work and sometimes cabinetry cuts

A built-in microwave sits inside your cabinet and is held in place by a mounting bracket, not just plugged in like a countertop model. Replacing one means disconnecting the power, removing the old unit from the cabinet opening, and installing a new one in its place. The electrical connection is the most important part—you need to know whether your microwave is hardwired (connected directly to the house circuit) or plugged into an outlet behind the cabinet. If it is hardwired, you should hire a licensed electrician to disconnect and reconnect it. If it is plugged in, you can do the swap yourself.

The whole job typically takes two to four hours if you are comfortable with basic tools and the new microwave is the same size as the old one. If the new unit is a different size, you may need to cut or patch drywall and cabinet material, which adds time and complexity. Before you start, measure the opening, check the power setup, and confirm that your new microwave will fit.

Key Takeaways

  • Built-in microwaves are held in by a mounting bracket inside the cabinet, and you must disconnect the power before removing anything.
  • If your microwave is hardwired to a circuit breaker, hire an electrician to disconnect and reconnect it; if it is plugged into an outlet, you can do it yourself.
  • Measure the cabinet opening width, height, and depth, and check the new microwave's trim kit dimensions to confirm it will fit without cabinet modification.
  • The mounting bracket bolts to the cabinet frame from inside, and you will need a socket wrench or adjustable wrench to remove and install it.
  • If the new microwave is smaller than the opening, you will need to install a filler panel or trim kit to close the gap.

Check the power connection before you touch anything

Open the cabinet below or beside your microwave and look behind it. You will see either a power cord plugged into an outlet, or wires running into a junction box. If there is a cord and outlet, you can unplug it and do the replacement yourself. If there are wires in a junction box, the microwave is hardwired and you need an electrician.

Even if you see a cord, turn off the circuit breaker that controls the microwave before you unplug it. The breaker is usually labeled "microwave" or "kitchen" in your electrical panel. Flip it to the off position and test that the microwave no longer powers on by pressing a button. This step takes one minute and prevents a shock.

Measure the opening and compare it to the new unit

Measure the width, height, and depth of the cabinet opening where the microwave sits. Use a tape measure and write down the numbers. Then measure the width and height of the trim kit (the frame that shows around the microwave) on your new unit—this is different from the microwave's actual size. The trim kit dimensions are what matter for fit.

Check the depth too. Built-in microwaves need clearance behind them for ventilation and the power connection. If your cabinet is shallow, the new microwave may not fit. Most built-in microwaves are 27 to 30 inches wide, 17 to 18 inches tall, and 15 to 16 inches deep. If your opening is significantly smaller or larger, you may need a custom trim kit or cabinet work.

Remove the old microwave from the cabinet

With the power off, open the microwave door and look inside the top corners. You will see two or four bolts or screws holding the mounting bracket to the cabinet frame. Use a socket wrench or adjustable wrench to remove these bolts. Keep them in a small container so you do not lose them.

Once the bolts are out, carefully pull the microwave toward you. It will slide out of the cabinet opening. If it is plugged in, the cord will come with it. If it is hardwired, the wires will be connected to a junction box—do not touch these wires; your electrician will handle them. Set the old microwave on a sturdy surface or the floor. Do not drop it.

Install the mounting bracket on the new microwave

Your new microwave comes with a mounting bracket and hardware. The bracket is usually a metal frame that bolts to the sides of the microwave cabinet. Follow the manufacturer's instructions to attach it. Most brackets bolt on from the inside of the microwave, so you will be working inside the cabinet space, not inside the cooking chamber.

Tighten all bolts firmly but do not overtighten—you can crack the microwave's casing. Once the bracket is find, check that it is level and square. The bracket needs to be aligned correctly so the microwave sits flush with the cabinet opening.

Slide the new microwave into the opening and find it

Carefully lift the new microwave and align it with the cabinet opening. The mounting bracket should slide into the opening first. Push the microwave in slowly and make sure the trim kit sits flush against the cabinet face. If the opening is larger than the trim kit, you will see gaps—you can fill these with a filler panel later.

Once the microwave is fully inserted, reach behind it and bolt the mounting bracket to the cabinet frame using the bolts you removed from the old unit (or new bolts if the old ones do not fit). Tighten them evenly so the microwave does not tilt. Check that the door opens and closes smoothly and that the microwave is level.

Connect the power and test the unit

If the old microwave was plugged in, plug the new one into the same outlet. If it was hardwired, your electrician will make the connection now. Once the power is connected, turn the circuit breaker back on. Press the microwave's power button to confirm it turns on. Set the time, run it for 30 seconds on high with a cup of water inside to test that it heats.

If the microwave does not power on, turn the breaker off again and check that the plug is fully inserted or that the electrician's connections are tight. If you still have no power, call the electrician or the microwave manufacturer's support line.

Fill gaps if the new microwave is smaller than the opening

If your new microwave's trim kit is narrower or shorter than the cabinet opening, you will see gaps around the edges. Most microwave manufacturers sell filler panels or trim kits for their models. Measure the gap and order the correct filler from the microwave maker or a kitchen appliance retailer.

Filler panels are usually thin metal or plastic frames that screw or snap into place around the trim kit. Installation takes 15 to 30 minutes and requires only a screwdriver. If a filler panel is not available for your model, a cabinet maker can build a custom panel to match your cabinetry, but this costs more and takes longer.

Frequently Asked Questions

Can I replace a built-in microwave with a countertop model?

Yes, but you will have an empty cabinet opening. You can leave it open for storage, install a shelf inside, or have a cabinet maker build a door or panel to close it. Removing the cabinet opening entirely requires carpentry and is usually not worth the cost unless you are renovating the kitchen.

What if the new microwave is larger than the old opening?

You cannot install it without cutting the cabinet. A cabinet maker can enlarge the opening, but this is expensive and time-consuming. It is easier to choose a microwave that fits your existing opening. Measure carefully before you buy.

Do I need a new trim kit when I replace the microwave?

Most microwaves come with a trim kit. If your old trim kit is in good condition and the new microwave is the same size, you may be able to reuse it, but the manufacturer usually does not recommend this. It is safer to use the trim kit that comes with the new unit.

How long does it take to replace a built-in microwave?

Two to four hours if the new unit is the same size as the old one and you are comfortable with tools. If you need an electrician to disconnect a hardwired unit, add one to two hours for their visit. If the opening needs to be resized, add a full day or more for cabinet work.

What should I do with the old microwave?

Microwaves contain parts that should not go in the trash. Take it to an electronics recycling center, a scrap metal facility, or a donation center if it still works. Some retailers that sell microwaves also take old ones for recycling. Call ahead to confirm they accept microwaves.