What You Need to Know Before Starting
Replacing a built-in microwave is a job you can do yourself if you are comfortable working with basic hand tools and following electrical safety steps. The process takes two to four hours and involves disconnecting the old unit, removing it from the cabinet opening, and installing the new one in its place. You will need a screwdriver, a utility knife, and possibly a drill — most of the work is unbolting, sliding, and reconnecting.
The hardest part is not the removal itself but making sure the new microwave fits your existing cabinet opening and that you understand your electrical setup before you start. Built-in microwaves come in standard sizes, but your cabinet opening may not match exactly, and the power connection varies by model. Measure your opening and check your electrical panel before you buy the replacement unit.
Key Takeaways
- Turn off power at the circuit breaker before you touch any wiring, and test the outlet with a voltage tester to confirm the power is off.
- Measure the width, height, and depth of your cabinet opening, and check whether your new microwave will fit before you remove the old one.
- Most built-in microwaves are held in place by four bolts on the sides of the unit and a mounting bracket at the top — remove these and slide the unit straight out.
- The power cord plugs into an outlet inside the cabinet, or the microwave is hardwired directly to the electrical box — know which one you have before disconnecting.
- After installation, test the unit on a low power setting with a cup of water before you use it normally.
Measure Your Cabinet Opening and Check the Fit
Before you remove the old microwave, measure the opening where it sits. Use a tape measure to find the width, height, and depth of the space inside the cabinet, from the inside edges of the frame. Write these numbers down. Then measure the new microwave's dimensions — the manufacturer's spec sheet will list the exact size needed for the cabinet cutout, which is different from the overall size of the unit itself.
Check whether your new microwave will sit flush with your cabinets or whether it will stick out. Some models are designed to be recessed slightly, and others sit forward. If the opening is too small, you may need to have a carpenter adjust the cabinet frame, which is a separate job. If the opening is larger than the new unit, you can use trim or filler panels, which usually come with the microwave or are sold separately by the manufacturer.
Turn Off Power and Disconnect the Old Unit
Go to your electrical panel and turn off the circuit breaker that controls the microwave outlet. The breaker is usually labeled "microwave" or "kitchen," but if you are not sure, turn off the breaker and test the outlet inside the cabinet with a voltage tester to confirm the power is off. A voltage tester is a small handheld tool that lights up or beeps when it detects live electricity — you can buy one for ten to twenty dollars at any hardware store.
Once the power is off, open the cabinet doors and look at how the microwave is connected. If there is a power cord plugged into an outlet inside the cabinet, unplug it. If the microwave is hardwired — meaning the wires go directly into an electrical box in the wall or cabinet — you will need to disconnect the wires. Hardwired units have a junction box with wire nuts (the plastic caps that hold wires together) or a terminal block. Take a photo of the wire connections before you disconnect them so you know how to reconnect the new unit.
Remove the Mounting Bolts and Slide Out the Old Microwave
Most built-in microwaves are held in place by four bolts — two on each side of the unit, usually near the top and bottom. Use a screwdriver or socket wrench to remove these bolts. You may also see a mounting bracket bolted to the top of the microwave and to the cabinet frame — remove those bolts as well. Keep all the bolts in a small container so you do not lose them.
Once the bolts are out, carefully slide the microwave straight out toward you. It will be heavy — ask someone to help you support it as you pull. Do not tilt it or angle it, because the power cord (if it is plugged in) or the wires (if it is hardwired) may catch or tear. Slide it all the way out and set it on a sturdy surface or the floor. If the cord is still attached, lay the old microwave on its back on a towel so the cord does not get pinched.
Install the New Microwave and Reconnect Power
Before you slide the new microwave into the opening, check that the interior of the cabinet is clean and that there are no obstructions. If the new unit is smaller than the old one, you may need to install filler panels or trim around the edges — follow the manufacturer's instructions for these pieces.
Slide the new microwave into the opening slowly and carefully, making sure the power cord or wires have room to move and will not be pinched. Once it is in place, align it so it sits flush with the cabinet frame. Then reconnect the power. If the old unit was plugged in, plug the new one into the same outlet. If the old unit was hardwired, you will need to connect the wires from the microwave to the wires in the electrical box using wire nuts or a terminal block, matching the connections you photographed earlier. If you are not confident working with electrical wires, hire a licensed electrician to do this step.
Once the power is connected, reinstall the mounting bolts on the sides and top of the microwave, tightening them firmly but not so hard that you crack the cabinet. Turn the circuit breaker back on and test the microwave on a low power setting with a cup of water inside for one minute before you use it normally.
Common Mistakes to Avoid
The most common mistake is not turning off the power before you start. Even if you are only removing bolts, a stray tool or wet hand near the electrical connections can cause a serious shock. Always turn off the breaker and test the outlet first.
The second mistake is not measuring the new microwave before you remove the old one. If the new unit does not fit, you will have an empty cabinet opening and no way to use the space until you buy a different model or have the opening enlarged. Measure twice and check the manufacturer's spec sheet before you start.
A third mistake is tilting or angling the microwave as you pull it out, which can damage the power cord or tear the wires. Slide it straight out, and have someone help you support the weight so you do not strain yourself or drop it.
When to Call a Professional
If your microwave is hardwired and you are not comfortable working with electrical connections, hire a licensed electrician to disconnect the old unit and connect the new one. The cost is usually fifty to one hundred fifty dollars, depending on your area, and it is worth it to avoid a fire or electrical hazard.
If your cabinet opening does not match the size of the new microwave and you cannot use filler panels to close the gap, you may need a carpenter to adjust the frame. This is a separate job that can cost several hundred dollars, so measure carefully before you buy the replacement unit.
If you are not sure which circuit breaker controls the microwave, or if you cannot find the electrical connections inside the cabinet, stop and call a professional. Do not guess — a wrong breaker or a missed connection can damage the new unit or create a safety hazard.
Frequently Asked Questions
Do I need a new mounting bracket for the new microwave?
Most built-in microwaves come with a mounting bracket in the box. Check the contents list before you buy the unit. If your new microwave uses the same bracket as the old one, you can reuse it — but measure to make sure it fits the new unit's dimensions.
What if the new microwave is smaller than the old one?
You will have gaps around the edges. The manufacturer usually sells trim kits or filler panels that match the microwave's finish. Install these panels in the gaps so the opening looks finished and to prevent heat or steam from escaping into the cabinet.
Can I use an extension cord if the power outlet is too far away?
No. Built-in microwaves draw a lot of power, and an extension cord can overheat and cause a fire. If the outlet is not in the right place, hire an electrician to install a new outlet closer to where the microwave will sit.
How do I know if my microwave is hardwired or plugged in?
Open the cabinet and look inside. If you see a power cord with a plug end, it is plugged into an outlet. If you see wires going directly into a box in the wall or cabinet with no plug, it is hardwired. Take a photo before you disconnect anything.
What should I do with the old microwave?
You can donate it to a thrift store, sell it online, or take it to an electronics recycling center. Do not put it in the trash — microwaves contain materials that should be recycled. Check your local waste management website for recycling options in your area.