What you need to know before you start

Replacing an over-the-stove microwave is a job most homeowners can do themselves in two to three hours, but it depends on whether your new unit fits the same space and uses the same electrical connection. The old microwave is usually bolted to the underside of a cabinet and plugged into an outlet behind it. You will need a helper to support the weight while you unbolt it—these units weigh 60 to 80 pounds—and you should turn off power at the breaker before you touch any wiring.

The hardest part is usually not the removal but the fit. Over-the-stove microwaves come in standard widths (30 inches is most common), but the mounting bracket, vent location, and electrical requirements vary by model. If your new microwave is a different brand or significantly older or newer than the one you are replacing, you may need to drill new holes, reroute venting, or have an electrician move the outlet. This guide covers the straightforward swap where the new unit matches the old one's dimensions and electrical setup.

Key Takeaways

  • Turn off the circuit breaker that powers the microwave before you disconnect anything, and test the outlet with a voltage tester to confirm power is off.
  • You will need a helper to hold the old microwave while you unbolt the mounting bracket from the cabinet above, because the unit is too heavy and awkward to manage alone.
  • Check the new microwave's mounting bracket, vent duct size, and electrical cord length against your existing setup before you begin removal.
  • If the new unit does not fit the same space or requires a different outlet location, stop and call a licensed electrician or appliance installer rather than improvising.

Turn off power and gather your tools

Locate the circuit breaker that controls the microwave outlet. It is usually labeled "microwave" or "kitchen" on the breaker panel. Switch it to the off position. Then go to the outlet behind the microwave and use a non-contact voltage tester (a battery-powered tool that beeps near live electricity) to confirm the power is actually off. Do not skip this step—it takes 30 seconds and prevents a serious shock.

Gather a helper, a cordless drill or screwdriver set, a socket wrench or adjustable wrench, a voltage tester, a flashlight, and a step stool or ladder. Have your new microwave unpacked and ready nearby so you can check its bracket and cord before you remove the old one. If the new unit came with installation instructions, read them now—they will tell you the exact mounting points and clearances you need.

Remove the old microwave

Open the microwave door and look underneath the cabinet above it. You will see a metal mounting bracket bolted to the underside. These are usually held by four bolts—two on each side—that go through the bracket and into the cabinet. Have your helper stand on a step stool and support the microwave from below while you unbolt the bracket from above. Work slowly; the unit will shift as you remove each bolt.

Once the bolts are out, the microwave will rest on your helper's hands. Carefully slide it straight out toward you. Do not tilt it or let it hang by the power cord. Set it down on a sturdy surface or the floor. Now you can unplug the cord from the outlet behind it. If the cord is hard to reach, use a flashlight to see into the space. Some older units have the cord plugged into a junction box rather than a standard outlet—if that is the case, you may need to call an electrician to disconnect it safely.

Check the new microwave against your space

Before you install anything, compare the new unit to the old one. Check the width, depth, and height. Look at where the mounting bracket bolts attach—they should line up with the holes in the cabinet above. If the holes do not match, you will need to drill new ones, which is doable but requires precision. Check the vent duct: if the old microwave vented through the cabinet and the new one does too, the duct should still fit. If the duct size or location is different, you may need to modify the ductwork or have it done by a professional.

Check the power cord. It should reach the outlet behind the microwave without stretching. If it is too short, you cannot use an extension cord—you will need an electrician to move the outlet closer. If the new unit has a different plug type or voltage requirement than the old one, stop here and call an electrician. Mismatched electrical setups are a fire hazard.

Install the mounting bracket and find the new unit

Position the new microwave's mounting bracket against the underside of the cabinet. Use a level to make sure it is straight. Mark the bolt holes with a pencil or a drill bit. If the holes do not line up with the old ones, you will need to drill new holes. Use a drill bit slightly smaller than the bolts—usually 3/16 inch for standard microwave bolts. Drill slowly and carefully; the cabinet is usually plywood or particle board and splinters easily.

Once the holes are ready, have your helper support the new microwave from below while you bolt the bracket to the cabinet. Tighten the bolts firmly but do not over-tighten—you can crack the cabinet. The microwave should not shift or rattle when you push on it gently. Plug the power cord into the outlet and turn the breaker back on. Test the microwave on a short cycle to make sure it powers on and heats.

Reconnect venting and check for gaps

If your microwave vents to the outside (rather than recirculating air back into the kitchen), check that the vent duct is still connected and sealed. The duct usually clips or screws to the back of the microwave. If it came loose during removal, push it back on firmly. If you had to remove it to get the old unit out, reconnect it now and make sure the connection is tight—loose venting reduces the microwave's ability to remove steam and odors.

Check the gaps around the microwave. There should be no large spaces between the unit and the cabinet or countertop. If there are, the new microwave may be slightly smaller than the old one. Small gaps (less than 1/4 inch) are normal and do not affect function. Larger gaps can be covered with trim or filler strips, which most appliance stores sell. If the microwave is noticeably loose or tilted, remove it and check the mounting bracket again.

When to call a professional

Call a licensed electrician if the new microwave's power cord does not reach the outlet, if the outlet is in the wrong location, or if the new unit requires a different voltage or amperage than the old one. Do not try to extend the cord with an extension cord or splice wires together—these are fire hazards in a kitchen.

Call an appliance installer if the new microwave does not fit the space, if the mounting bracket holes do not line up and you are not comfortable drilling new ones, or if the vent duct needs to be rerouted. These professionals have the tools and experience to handle unusual situations and can usually finish the job in an hour or two. The cost is typically $100 to $200, which is worth it to avoid damaging your cabinet or creating an unsafe installation.

Frequently Asked Questions

Can I install a microwave that is a different size than the old one?

Only if it is smaller. A larger microwave will not fit the space. A smaller one will work, but you will have visible gaps that may need trim to look finished. Check the width, depth, and height of both units before you buy the new one.

What if the mounting bracket bolts do not line up with the cabinet holes?

You will need to drill new holes. Use a drill bit slightly smaller than the bolts and drill slowly to avoid splitting the cabinet. If you are not comfortable doing this, an appliance installer can do it in minutes.

Do I need to turn off the breaker if I am just unplugging the microwave?

Yes. Even though you are unplugging it, the outlet is still live with electricity. Turning off the breaker is the safest way to work on anything electrical.

What should I do with the old microwave?

Most appliance stores will haul away your old microwave for free or a small fee when you buy a new one. You can also contact your local waste management to learn about they have a bulk pickup day or an appliance recycling program.

How long does the installation usually take?

Two to three hours if everything lines up and you have a helper. It takes longer if you need to drill new mounting holes or reroute venting. If you run into unexpected problems, stop and call a professional rather than forcing something that does not fit.