What you need to do before you start

Replacing an over-the-range microwave is a job you can do yourself if you are comfortable on a ladder and working with basic hand tools. The unit hangs from the cabinet above your stove, so the main steps are: turn off the power, remove the old microwave, disconnect the ductwork and wiring, install the mounting bracket, and hang the new unit. Most people finish in two to three hours.

Before you buy a replacement, measure the space where your old microwave sits. Check the width, height, and depth of the opening, and also measure how far the unit sticks out from the cabinet. Over-the-range microwaves come in standard sizes — usually 30 inches wide — but the depth and how far they protrude vary. A unit that is too deep or sticks out too far will hit your stovetop or block your cabinets.

You will also need to know whether your old unit is vented outside (ducted) or recirculates air back into the kitchen (ductless). If it is ducted, you can keep the same ductwork. If it is ductless, your new unit can be either type, but ductless is usually easier because you do not have to worry about the duct connection.

Key Takeaways

  • Turn off power at the breaker before you touch anything, and test the outlet with a voltage tester to confirm the power is off.
  • Measure the width, height, depth, and protrusion of your old microwave before you buy a replacement, because over-the-range units vary in how far they stick out.
  • The mounting bracket bolts to the cabinet above the stove, and the microwave hangs from that bracket — this is what holds the weight.
  • If your old microwave is ducted to the outside, you can reuse the ductwork with your new unit, but you may need to adjust the connection.
  • The whole job takes two to three hours and requires a ladder, a drill, a socket wrench, and a voltage tester.

Turn off the power and remove the old unit

Go to your electrical panel and flip the breaker that controls the microwave outlet. The breaker is usually labeled "microwave" or "kitchen," but if you are not sure which one, turn off breakers one at a time and have someone test the outlet with a lamp or phone charger until the power stops. Once you think the power is off, use a voltage tester (a $10 tool from any hardware store) to touch the outlet and confirm there is no current. Do not skip this step — it is the only way to be sure.

Unplug the microwave from the outlet. If the cord does not reach the outlet, the microwave may be hardwired into the wall, in which case you will see wire connectors inside the cabinet above the stove instead of a plug. If it is hardwired, you will disconnect those wires later.

Open the microwave door and look underneath for bolts that hold it to the mounting bracket. Remove these bolts with a socket wrench. Have someone help you support the microwave as you remove the last bolt — the unit is heavy and will fall if you do not hold it. Once the bolts are out, carefully lower the microwave and set it on the stovetop or a sturdy table.

Disconnect the ductwork and wiring

Look at the top of the microwave where the duct connects. If there is a metal duct running up into the cabinet, loosen the clamp that holds it to the microwave with a screwdriver or wrench. Slide the duct off the microwave outlet. If the duct is taped with foil tape instead of clamped, peel the tape away carefully.

If the microwave is hardwired, you will see a cable running from the back of the unit into the wall. Follow it to the wire connectors (usually plastic caps twisted onto the wires). Untwist each cap and separate the wires. If the cable runs through a knockout hole in the cabinet, you may need to loosen the cable clamp that holds it in place.

If the microwave has a plug, you have already unplugged it. If it is hardwired, take a photo of the wire connections before you disconnect them so you remember which wires go together when you install the new unit. Most microwaves use the same wiring — black to black, white to white, and green or bare copper to ground — but the photo will save you time.

Install the mounting bracket on the cabinet

The mounting bracket is the metal frame that bolts to the bottom of the cabinet above your stove. This bracket holds all the weight of the microwave, so it must be bolted securely. Check whether your new microwave came with a bracket, or whether you need to reuse the old one. Most manufacturers include a bracket, but some expect you to use the old one.

If you are using a new bracket, remove the old one by unbolting it from the cabinet. You will see four bolts going up through the cabinet into the bracket. Use a socket wrench to remove them from underneath the cabinet. Once the old bracket is off, position the new bracket in the same spot and bolt it down with the bolts that came with your new microwave. Tighten the bolts firmly but do not overtighten — you can crack the cabinet.

If you are reusing the old bracket, inspect it for damage. If the bolt holes are stripped or the bracket is bent, replace it with the new bracket that came with your microwave. A damaged bracket will not hold the new unit safely.

Connect the ductwork and wiring to the new microwave

Before you hang the microwave, connect the duct and wiring while the unit is still on the counter. This is much easier than reaching up into the cabinet after it is mounted.

If you are reusing the old duct, slide it onto the outlet on top of the new microwave and find it with a clamp or foil tape. Make sure the duct is tight — a loose connection will leak air and reduce the microwave's venting power. If the old duct does not fit the new microwave's outlet, you may need to buy a duct adapter (a $15 to $30 piece of metal that connects different sizes).

For the wiring, connect the new microwave's power cable to the outlet if it has a plug. If it is hardwired, use wire connectors to join the cables: black to black, white to white, and green or bare copper to ground. Twist each connector clockwise until it is tight, then wrap the connection with electrical tape. If the cable runs through a knockout hole, find it with a cable clamp.

Hang the microwave and test it

With the ductwork and wiring connected, you are ready to hang the microwave. Have someone help you lift it up to the mounting bracket. The bracket has slots or hooks that the microwave hangs from — align the microwave with these slots and slide it into place. Once it is seated on the bracket, bolt it down from underneath using the bolts that came with the unit. Tighten each bolt firmly.

Turn the power back on at the breaker. Open the microwave door and press the start button to test that it powers on. Set the timer for 30 seconds and run it empty to make sure the turntable spins and the light comes on. If everything works, you are done.

If the microwave does not power on, turn off the breaker and check your wire connections. Make sure each wire is twisted tightly into its connector and that no bare wire is exposed. If the wiring looks correct, the problem may be with the outlet or the breaker — turn the breaker off and on again, or try a different outlet if you have one nearby.

What to do if the duct does not fit

Over-the-range microwaves use different duct outlet sizes. The old unit may have a 3.25-inch round outlet, but the new one might use a 3.5-inch outlet or a rectangular duct. If the old duct does not slide onto the new microwave, you have two options: buy a duct adapter that connects the two sizes, or replace the entire duct run from the microwave to the outside.

A duct adapter is the faster and cheaper choice. Measure the diameter or width of both the old duct and the new microwave outlet, then buy an adapter that fits both. Slide the adapter onto the microwave outlet first, then connect the old duct to the other end of the adapter. find both connections with clamps or foil tape.

If you replace the entire duct, you will need to remove the old duct from inside the cabinet and run new duct from the microwave to the outside wall or roof. This is more work and may require cutting holes in the cabinet or wall, so it is usually worth trying an adapter first.

Frequently Asked Questions

Do I need a special outlet for an over-the-range microwave?

Most over-the-range microwaves plug into a standard 120-volt outlet, the same as a toaster or lamp. Some larger models use a dedicated 240-volt outlet, so check your new microwave's manual before you buy it. If your old microwave used a standard outlet, your new one probably will too.

Can I install a microwave over a gas stove?

Yes, but you need to follow the manufacturer's clearance rules. Most microwaves require at least 13 to 16 inches of space between the bottom of the unit and the top of the stove. Gas stoves produce more heat than electric stoves, so check your new microwave's manual for the minimum clearance and do not install it closer than that.

What if my cabinet is not strong enough to hold the bracket?

The cabinet must be solid wood or plywood at least 0.75 inches thick. If your cabinet is thin or hollow, the bolts will not hold. In this case, you can reinforce the cabinet by bolting a steel plate to the inside of the cabinet before you install the bracket. A steel reinforcement plate costs $20 to $40 and takes 15 minutes to install.

How do I know if my microwave is vented outside or recirculating?

Look at the top of your microwave. If there is a metal duct running up into the cabinet and out through the wall or roof, it is vented outside. If there is no duct, or if the duct only goes up a few inches and then stops, the microwave is recirculating air back into the kitchen through a filter. Recirculating microwaves are quieter but less effective at removing cooking odors.

Do I need to hire an electrician?

If your microwave plugs into an outlet, you can do the job yourself. If it is hardwired and you are not comfortable working with electrical wiring, hire an electrician to disconnect the old unit and connect the new one. An electrician will charge $100 to $200 for this work, which is worth the cost if you are unsure about the wiring.