ElectricalToolbox

Can You Run a Roaster Oven and Microwave on the Same Circuit?

Not reliably, and on Thanksgiving almost certainly not. An electric roaster oven holding the turkey draws about 12 amps, and a microwave pulls roughly 10 to 13 amps from the wall while it runs. Add them up and you are near 24 amps on a circuit built for 20. The breaker does its job and shuts off, usually the moment someone starts the microwave while the roaster's heating element is on. The fix is simple: put the roaster on one kitchen circuit and the microwave on the other, so neither one is sharing with a second heavy load.

Read the input wattage off each appliance's nameplate, divide by 120 to get amps, and total them against the circuit's budget on the Continuous Load Calculator. Two appliances near 12 amps each will not share one 20-amp circuit. Split them across your two kitchen circuits.

The short version

  • A roaster oven is about 12 amps. A common 1,450-watt unit draws roughly 12 amps and runs for hours, so it is a steady, heavy load.
  • A microwave is 10 to 13 amps. Size it on the input watts on the back panel, not the cooking-watts number on the front.
  • Together they overrun a 20-amp circuit. About 24 amps on a circuit rated for 20 trips the breaker.
  • Kitchens have two counter circuits for this reason. Put one appliance on each, not both on one.
  • Nearby outlets can share a breaker. Map them before you plug in two big loads side by side.

Read the input watts, not the cooking watts

A microwave carries two different wattage numbers, and mixing them up is the most common mistake in this math. The big number on the front, the "1,000-watt" or "1,100-watt" rating, is cooking power, the energy delivered to the food. What the microwave pulls from the outlet is the input power, and it is always higher because the magnetron is not perfectly efficient. A microwave rated 1,000 watts of cooking power commonly draws 1,200 to 1,700 watts at the wall. The input figure is on the nameplate on the back or bottom, often listed directly in amps. That input number is the one that sets the circuit load.

The worked numbers

Current is wattage divided by voltage. Take an 18-quart roaster oven at 1,450 watts and a countertop microwave with a 1,500-watt input nameplate, both on 120 volts:

Roaster: 1,450 W ÷ 120 V ≈ 12.1 A

Microwave: 1,500 W ÷ 120 V = 12.5 A

Together: 12.1 + 12.5 = 24.6 A

A kitchen counter circuit is rated 20 amps. At 24.6 amps the pair is nearly five amps over that, so the breaker trips as soon as both are drawing at once. Even a modest microwave softens the result only a little: a 1,200-watt input unit is 10 amps, and 10 plus the roaster's 12.1 is still 22.1 amps, over a 20-amp circuit. There is no combination of a full-size roaster and a real microwave that fits on one 20-amp circuit with margin to spare.

20-amp circuit × 80% = 16 A usable for a continuous load

Roaster alone: 12.1 A, fits a dedicated 20-amp circuit

Roaster + microwave: 22 to 25 A, over the 20-amp rating

The roaster on its own is fine: at 12.1 amps it sits well under a 20-amp circuit's ceiling, and since it runs the bird for three or four hours it counts as a continuous load, so the 16-amp continuous budget is the one to check it against. It is the second heavy appliance that breaks the circuit. Total your own two nameplates on the Continuous Load Calculator.

Your kitchen already has the answer built in

The code has required at least two separate 20-amp small-appliance circuits for kitchen counter receptacles since long before your house was wired, precisely because countertops run heavy loads. The two circuits usually alternate across the outlets, so the plug by the stove and the plug by the sink are often on different breakers. That is the tool you have: put the roaster on one circuit and the microwave on the other, and each heavy load gets its own 20 amps. The trouble starts when both appliances end up plugged into outlets that happen to share one breaker.

Map the circuits before the meal, not during it

You cannot tell which outlets share a breaker by looking. Two receptacles a few feet apart may be on one circuit; two on opposite walls may be on two. Find out in advance: plug a lamp into each counter outlet, switch off one kitchen breaker, and note which lamps go dark. Do it for both kitchen breakers and you have a map of which outlets are independent. Then place the roaster and the microwave on outlets you have confirmed are on different circuits. A plug-in outlet tester with a breaker-finder makes the same map without the lamps. Doing this the day before beats discovering the overlap when the turkey is half-cooked and the breaker drops.

A tripped breaker and a dead outlet are not the same

If the outlet goes dead, check which thing actually opened. An overload trips the circuit breaker in the panel, and you reset it there. A kitchen counter outlet is also GFCI-protected, and a GFCI trips on a ground fault, often from a splash or a failing appliance, and resets at the little button on the outlet itself, which may be an outlet upstream of the dead one. If the breaker keeps tripping the instant you add the second appliance, that is overload, and the answer is to move a load, not to keep resetting. Thanksgiving is the single busiest day of the year for home cooking fires, with an estimated 1,446 home cooking fires reported on Thanksgiving Day 2023, more than three times the daily average, per the NFPA, so a circuit that keeps overloading is worth fixing, not forcing.

The safer setup

  • One heavy appliance per circuit. Roaster on one kitchen circuit, microwave on the other, never both on one.
  • Size on input watts. Use the back-panel nameplate, not the cooking-watts number on the door, divided by 120.
  • Map the outlets first. Confirm which counter outlets are on different breakers before the meal starts.
  • Run the roaster on a dedicated circuit when you can. At 12 amps for hours it is happiest with nothing else on the breaker.
  • Do not keep resetting an overload. If the breaker drops every time the second load comes on, move the load instead.

NEC reference

National Electrical Code (NEC) 2020. Kitchen countertop receptacles must be served by two or more 20-amp small-appliance branch circuits under 210.52(B)(1) and 210.11(C)(1), and those receptacles require GFCI protection under 210.8(A)(6). A load expected to run three hours or more is a continuous load under the Article 100 definition, and a branch circuit is limited to 80 percent of its rating for a continuous load under 210.19(A) and 210.20(A), which is 16 amps on a 20-amp circuit; a roaster holding the turkey for hours is that kind of load, while a microwave runs in short bursts. The wattage and amp figures here are typical product-label values, not code values, and watts equal volts times amps is the power relationship, not a code figure; your own nameplates govern. The Thanksgiving cooking-fire figure is NFPA data for 2023.

Results are for reference only. Verify against the applicable adopted edition of the NEC and consult a licensed electrician for code compliance.

For the whole season

The Holiday Electrical Safety Handbook

This guide answers one question. The Handbook covers Halloween through New Year's: how many amps a circuit can really carry (a 15 amp breaker means 12 amps, a 20 means 16), extension cords, GFCI outlets, outdoor displays in the weather, the Thanksgiving kitchen, tree lights, space heaters, and what to do when something goes wrong. Every figure is pre-converted to amps, so you add instead of calculate.

Read on Kindle Paperback on Amazon Free circuit map and load worksheet

Get the next seasonal safety check by email

Optional. Short emails before each holiday, written for homeowners.

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