A 1,000W microwave draws roughly 12-14 amps on a standard 120V circuit — not the 8.3A you get from dividing the number on the door by 120. That gap is the whole story of this article, and it is where most advice pages get the arithmetic wrong.
The number on the door is not the number on the breaker
Every microwave carries two power figures, and only one of them is on the wall wattage that matters for amps. The number on the front — “1,000W”, “900W”, “700W” — is cooking power, the energy actually delivered into your food by the magnetron. The number that draws current from your outlet is input power, and it is always higher, because only part of the input reaches the food. On makers’ own spec pages, cooking power works out to 63-73% of input for the three standard models in the nameplate table below and 81-86% for Panasonic’s two inverter models. The rest is lost as heat inside the unit, which is also why a microwave’s vents run warm.
So a “1,000W” microwave is actually pulling somewhere between 1,430W and 1,670W from the wall, depending on the specific magnetron’s efficiency. Divide that by 120V and you get 11.9-13.9 amps — not 8.3A. This is a real and common mistake: retailers, spec sheets aimed at casual buyers, and even some appliance manuals lead with the cooking figure because it is the marketing number, and readers doing the amps calculation themselves plug it straight into Watts ÷ Volts and end up almost 40% low.
Amps by cooking wattage, at 120V
Use the input-wattage column, not the cooking-wattage column, whenever you’re sizing a circuit, an extension cord, or an inverter. The 600-1,000W rows assume cooking power is 60-70% of input. The three standard models in the nameplate table below land at 63-73%, so that range covers them or slightly overstates their draw, which is the safe direction when sizing. The 1,200W row uses makers’ published input figures instead: 1,400-1,480W for Panasonic’s two 1,200W inverter models in that table, and 1,650W for GE’s 1,200W JES2251SJ countertop model, which GE lists at 13.9A. Conventional 1,200W models from other makers list up to about 1,850W, so plan on 1,800W when sizing.
| Cooking power (on the door) | Input power (at the wall) | Amps at 120V |
|---|---|---|
| 600 W | 860 – 1,000 W | 7.1 – 8.3 A |
| 700 W | 1,000 – 1,170 W | 8.3 – 9.7 A |
| 900 W | 1,290 – 1,500 W | 10.7 – 12.5 A |
| 1,000 W | 1,430 – 1,670 W | 11.9 – 13.9 A |
| 1,200 W | 1,400 – 1,850 W | 11.7 – 15.4 A |
The exact figure for your unit is on its rating label, usually on the back or inside the door frame, listed as amps directly — use that number over any estimate if you have it. When you’re working from the cooking wattage alone, our watts to amps calculator does the same division once you’ve estimated the input figure; the amps to watts calculator is the one to reach for if you’re starting from a breaker’s rating instead.
What real nameplates say
Makers publish both numbers, and the gap between them depends on the design. These five models list cooking power and input power on their makers’ own spec pages:
| Model | Cooking power | Input power (maker) | Cooking ÷ input | Amps at 120V (input ÷ 120) |
|---|---|---|---|---|
| Panasonic NN-SC67NS, 1.3 cu ft countertop, inverter | 1,200 W | 1,400 W | 86% | 11.7 A |
| Panasonic NN-SN686S, 1.2 cu ft countertop, inverter | 1,200 W | 1,480 W | 81% | 12.3 A |
| Panasonic NN-SU696S, 1.3 cu ft countertop | 1,100 W | 1,500 W | 73% | 12.5 A |
| GE JES1460DSBB, 1.4 cu ft countertop | 1,100 W | 1,600 W | 69% | 13.3 A |
| GE JVM3160DFBB, 1.6 cu ft over-the-range | 1,000 W | 1,580 W | 63% | 13.2 A |
Panasonic’s two inverter models turn 81-86% of their input into cooking power, so a 1,200W inverter unit such as the NN-SN686S (1,480W input, about 12.3A) draws less than the 1,000-1,100W standard models below it. The three standard models land at 63-73%. Where a maker also prints amps, that figure can run above watts divided by 120: GE lists 13.5A for the JES1460DSBB and 15A for the JVM3160DFBB. Your own microwave’s rating label is the number to use; this table only shows how far real models stray from a single rule of thumb.
Countertop, over-the-range, and built-in
The three common formats sit at different points on that table, and it affects wiring more than most buying guides mention.
- Countertop microwaves plug into a standard outlet and mostly cluster at 600-900W cooking power for compact and mid-size units, 900-1,200W for full-size ones. That puts full-size countertop models at 11-14A input — close to or over the 12A limit for a single plug-in appliance on a 15A circuit.
- Over-the-range (OTR) microwaves run 900-1,000W cooking power in most residential kitchens and typically ship with manufacturer instructions specifying a dedicated circuit, because they’re hardwired or on a captive plug and share the kitchen’s electrical load with everything else on the counter.
- Built-in and drawer microwaves often sit at the higher end, 1,000-1,200W cooking power, because they’re marketed as a range replacement and need to close the cooking-speed gap. These are the units most likely to need a genuine 20A circuit and are usually installed by an electrician for that reason.
Why microwaves usually want a dedicated 20A circuit
On a circuit that feeds more than one outlet, the National Electrical Code limits any single cord-and-plug appliance to 80% of the circuit’s rating: 12A on a 15A circuit and 16A on a 20A circuit (NEC 210.23(A)(1) in the 2020 edition, 210.23(B)(1) in the 2023 edition). Equipment fastened in place, such as an over-the-range microwave, may use no more than 50% of a circuit that also supplies lights or plug-in appliances (210.23(A)(2) in the 2020 edition, 210.23(B)(2) in the 2023 edition). Which edition applies depends on what your state or town has adopted, so have a licensed electrician confirm the rules before adding or changing a circuit. Look back at the table: a full-size 1,000W microwave already draws 11.9-13.9A on its own, and a 1,200W unit draws 11.7-15.4A, with inverter models at the low end; plan on about 1,800W when sizing a circuit or power station. Put either of those on a 15A circuit with a toaster or coffee maker running at the same time and you will trip the breaker — not because anything is wrong with the microwave, but because the math no longer fits.
That is why manufacturer instructions for over-the-range and built-in models almost always specify a dedicated 20A, 120V circuit: the microwave alone is close to the 12A a single plug-in appliance may draw on a 15A circuit, and a dedicated circuit means nothing else competes for the remaining headroom. Kitchen code in most US jurisdictions already requires 20A “small appliance” circuits for countertop receptacles for the same reason — microwaves are one of the few common kitchen appliances that draw this much current on an ordinary 120V outlet.
Starting current and duty cycling
Compressor-driven appliances — refrigerators, freezers, air conditioners — pull a brief surge of 3-7x their running current when the motor starts, and that surge is what actually trips breakers and defeats undersized inverters. Our guide to refrigerator wattage covers that in detail. A microwave doesn’t have that problem in the same way: the magnetron and transformer draw close to their full input current almost as soon as you press start, with no multi-second inrush spike to plan around.
What a conventional transformer microwave does instead is duty-cycle. On these models, power levels below 100% (a “50%” setting, or a defrost cycle) don’t reduce the draw — they turn the magnetron fully on and fully off in short bursts, so the current on the circuit alternates between the full input figure and roughly zero rather than settling at a steady half-power draw. Inverter microwaves work differently: they turn the magnetron’s power down continuously, so a lower setting does draw less current. For sizing a circuit or an inverter, with either type you should plan around the full input wattage at 100% power, not an averaged-down figure, because that is the load a device sees the moment the magnetron switches on.
Running a microwave from a power station
Because a microwave’s draw is close to constant once it’s on, the number that matters when picking a portable power station is its continuous AC output rating, not its surge rating. A full-size 1,000W-cooking microwave can pull up to 1,670W at the wall; GE’s 1,000W over-the-range model above lists 1,580W. The BLUETTI Elite 100 V2 Portable Power Station and the EcoFlow DELTA 3 Classic Solar Generator are each rated for 1,800W of AC output and 1,024 Wh of capacity, according to BLUETTI and EcoFlow. That runs those microwaves, but with only 130-220W to spare, so treat an 1,800W station as the bare minimum for a full-size microwave rather than comfortable headroom: anything else plugged into the station at the same time eats into that margin. A station rated 2,000W or more gives real headroom. A 1,200W inverter model listed at 1,400-1,480W sits more easily on an 1,800W unit. For a compact or dorm-style microwave in the 600-700W cooking range (about 860-1,170W from the outlet), a smaller unit like the Anker SOLIX C800 Portable Power Station – 768Wh with a 1,200W AC rating can run it, though a 700W model leaves almost no margin.
Capacity decides how many minutes of cooking you get. BLUETTI’s runtime formula for the Elite 100 V2 multiplies its 1,024 Wh by a 90% depth of discharge and an inverter efficiency of over 85%, then divides by the load plus about 10W the station uses itself. Taking 85%, that leaves about 783 Wh: roughly 28 minutes of microwave-on time at 1,670W, 30 minutes at 1,580W and 32 minutes at 1,480W. Put your own microwave’s label figure into the same sum. Half an hour covers many short reheats, since a microwave is rarely on for more than a few minutes at a stretch, but not a long cook.
Whichever size you land on, check the actual price-per-watt-hour rather than the sticker price alone — capacity and output rise together across the power stations we track, and value doesn’t move in a straight line with price. Our power station price index tracks that across the current market. If a microwave is one appliance in a wider setup — alongside a fridge, a TV, or CPAP equipment — the full appliance wattage chart and the power station finder are the faster way to size the whole load rather than adding devices up one article at a time.
Standby power: capped by federal rule
A microwave that is plugged in but not cooking still draws a little power, and federal efficiency standards cap it. Under 10 CFR 430.32(j)(3), microwave-only ovens and countertop convection microwaves made from June 17, 2016 until June 22, 2026 may average no more than 1.0W in standby, and built-in and over-the-range convection models no more than 2.2W. Units made on or after June 22, 2026 are held to 0.6W and 1.0W.
On the grid that is small change. Left plugged in for all 8,760 hours of a year, 1.0W comes to about 8.8 kWh and 0.6W to about 5.3 kWh: roughly $1.60 and $0.96 a year at 18.31 cents per kWh, the US average residential price for July 2026 in the Energy Information Administration’s Electric Power Monthly.
On a power station, the station’s own draw matters more. BLUETTI lists the Elite 100 V2’s self-consumption at about 10W, so a microwave left plugged in with the AC output switched on costs roughly 11W around the clock: about 260 Wh a day, a quarter of the battery’s 1,024 Wh rating. Switch the AC output off between cook cycles.