What You Need to Know Before Starting

Replacing a range hood with a microwave is possible, but it requires careful planning because the two appliances have different venting needs and electrical demands. A range hood pulls cooking smoke and steam out of your kitchen through ductwork. A microwave heats food with radio waves and produces little to no exhaust—it either vents to the outside (like a hood) or recirculates air back into the kitchen. Before you remove anything, you need to understand what's currently installed, whether your electrical panel can handle a microwave, and whether your ductwork can be repurposed or needs to be sealed.

The job typically takes a full day if you're comfortable with basic tools and electrical work. If you're not, hire a licensed electrician for the wiring and possibly a contractor to handle ductwork. The cost of the microwave itself ranges widely—from $300 to $1,500 depending on size and features—but labor can add $500 to $2,000 if you hire professionals.

Key Takeaways

  • Turn off power at the breaker before touching any wiring, and confirm the power is off with a voltage tester.
  • Measure the opening where your range hood sits, because microwaves come in standard sizes (30 inches is most common) and may not fit the same space.
  • Decide whether to vent the microwave outside (using existing ductwork) or recirculate air back into the kitchen (which requires a charcoal filter but no ductwork changes).
  • The microwave will need its own electrical circuit if it draws more than 10 amps, which most over-the-range models do.
  • Seal or cap any ductwork you're not using, because open ducts let outside air and pests into your kitchen.

Measure the Opening and Check Clearances

Start by measuring the width, height, and depth of the space where your range hood currently sits. Most over-the-range microwaves are 30 inches wide, but some are 24 or 36 inches. The depth (front to back) is usually 15 to 17 inches, and the height is typically 16 to 20 inches. If your range hood opening is significantly larger or smaller, you may need to install a trim kit or have the cabinet opening modified.

Check the clearance above the microwave. Building codes require at least 13 to 15 inches of space between the top of your range and the bottom of the microwave. If your range hood is mounted lower, you may not have room for a microwave without moving cabinets or the range itself. Also measure the distance from the microwave to any walls or cabinets on the sides—most models need at least 1 inch of clearance on each side for air circulation.

Turn Off Power and Remove the Range Hood

Locate the circuit breaker that powers your range hood. It's usually a 20-amp breaker labeled "range hood" or "exhaust fan." Turn it off, then test the hood with a voltage tester to confirm the power is truly off. A voltage tester is a small handheld device (about $10 to $20) that lights up or beeps if electricity is present—do not skip this step.

Disconnect the wiring inside the hood. Most hoods have a wire connector (a plastic cap that twists off) where the hood's wires meet the house wiring. Untwist it and separate the wires. Take a photo of the wire connections before you disconnect them so you remember which wire was which. Unbolt the hood from the cabinet or wall—usually four to six bolts. Have a helper support the hood as you remove the last bolt, because it's heavy and can fall. Carefully pull the hood away from the wall and set it aside.

Decide on Venting: Outside or Recirculating

You now have two choices for how the microwave will handle cooking steam and odors. An externally vented microwave pulls air out of the kitchen through ductwork to the outside, just like your old hood did. This is more effective at removing odors and steam, but it requires ductwork and a vent opening in your exterior wall or roof. A recirculating microwave pulls air through a charcoal filter and pushes it back into the kitchen. It's easier to install (no ductwork needed) but less effective at removing odors, and you'll need to replace the filter every 6 to 12 months.

If your existing ductwork is in good condition and vents to the outside, you can reuse it with an externally vented microwave. If the ductwork is damaged, disconnected, or you prefer not to deal with it, choose a recirculating model. If you're not using the ductwork, you must seal or cap it at both ends—where it connects to the cabinet and where it exits the building—to prevent outside air, pests, and moisture from entering your home.

Prepare the Ductwork

If you're installing an externally vented microwave, inspect the existing ductwork. Look for dents, disconnections, or gaps. Flex ductwork (the accordion-style metal tube) can be reused if it's intact, but rigid ductwork should be checked for blockages. If the ductwork is damaged, you can replace it with new flex ductwork (about $30 to $60 for a 25-foot run) or hire a contractor to install rigid ductwork ($200 to $500).

If you're not using the ductwork, disconnect it from the cabinet opening and seal both ends. Use a duct cap (a metal or plastic cover, about $10 to $20) at the exterior vent opening, and seal the interior opening with aluminum foil tape or a duct plug. This prevents warm or cool air from escaping and keeps pests and moisture out.

Install the Mounting Bracket and Microwave

Most over-the-range microwaves come with a mounting bracket that attaches to the cabinet or wall studs above the range. Read the microwave's manual to find the exact mounting height—it's usually 13 to 15 inches above the range. Mark the stud locations with a pencil, then bolt the bracket to the studs using the bolts provided. Use a level to may support the bracket is straight.

If you're installing an externally vented model, connect the ductwork to the vent opening on the back or bottom of the microwave before you lift it into place. Use a duct connector (a metal sleeve that slides over the ductwork, about $5 to $10) and find it with hose clamps or duct tape. Lift the microwave onto the bracket with a helper—these units weigh 60 to 100 pounds—and bolt it to the bracket according to the manual. Tighten all bolts firmly but do not over-tighten, which can crack the microwave's housing.

Connect the Electrical Wiring

Before you connect any wires, confirm again that the power is off at the breaker and test with a voltage tester. Most over-the-range microwaves draw 10 to 15 amps and require a dedicated 20-amp circuit. If your old range hood was on a 15-amp circuit, you may need to upgrade to a 20-amp breaker and wire. This is a job for a licensed electrician if you're not experienced with electrical work.

If the existing wiring is adequate, connect the microwave's power cord to the house wiring using wire connectors. Typically, the black wire (hot) connects to black, the white wire (neutral) connects to white, and the bare copper or green wire (ground) connects to the ground. Twist the wires together, then screw on a wire connector and tug gently to confirm it's tight. Wrap the connection with electrical tape for extra security. Tuck all wires into the cabinet space above the microwave, then turn the breaker back on and test the microwave.

Seal Gaps and Test the Installation

Once the microwave is mounted and powered on, check for gaps between the microwave and the cabinet. If there are gaps larger than 1/4 inch, seal them with silicone caulk (about $5 per tube) to prevent steam and cooking odors from escaping into the cabinet. Let the caulk dry for 24 hours before using the microwave.

Run the microwave on high for 5 to 10 minutes and check that it heats food properly. If you installed an externally vented model, feel the ductwork and exterior vent to confirm air is flowing out. If you installed a recirculating model, make sure air is flowing back into the kitchen from the grilles on the sides or bottom of the unit. Check that the light and fan work, and that the turntable rotates smoothly. If anything doesn't work, turn off the power and review the manual or call the manufacturer's support line.

Frequently Asked Questions

Can I install a microwave if my range hood ductwork goes into the attic instead of outside?

No. Ductwork that vents into the attic allows moisture and cooking odors to accumulate there, which can damage insulation and promote mold growth. You must either extend the ductwork to the exterior or switch to a recirculating microwave. If you choose to extend it, hire a contractor—running ductwork through an attic or wall requires cutting holes and ensuring proper slope and support.

What if the microwave is too wide for the opening?

You have three options: install a trim kit (a frame that extends the opening, $50 to $150), have a carpenter widen the cabinet opening (usually $200 to $500), or choose a smaller microwave (24 inches instead of 30). Trim kits are the cheapest and fastest solution if one is available for your microwave model.

Do I need a new circuit breaker for the microwave?

Most over-the-range microwaves need a dedicated 20-amp circuit. If your range hood was on a 15-amp circuit, you'll need to upgrade the breaker and wire. A licensed electrician can assess your existing circuit and tell you whether an upgrade is necessary—this usually costs $200 to $400.

Can I use the old range hood ductwork with a recirculating microwave?

No. A recirculating microwave doesn't need ductwork because it filters and recirculates air back into the kitchen. If you install a recirculating model, you must seal or cap the old ductwork at both ends to prevent air leaks and pest entry.

How often do I need to replace the charcoal filter in a recirculating microwave?

Most charcoal filters need replacement every 6 to 12 months, depending on how much you cook. Some microwaves have a filter-change indicator light that tells you when it's time. Replacement filters cost $20 to $50 and are available from the microwave manufacturer or online retailers.