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 a magnetron converts household AC into microwave energy at roughly 60-70% efficiency. 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 range in each row reflects the 60-70% efficiency spread across magnetron designs.
| 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 | 1,710 – 2,000 W | 14.3 – 16.7 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.
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 11-17A input — close to or over the safe continuous draw of an ordinary 15A kitchen outlet on its own.
- 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
A standard 15A circuit is limited to 12A of continuous load under NEC 210.20 — the 80% rule that keeps a circuit from running hot indefinitely. A 20A circuit is limited to 16A continuous on the same rule. 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 14.3-16.7A. 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 filling a 15A circuit’s continuous-load allowance, 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 3-5x 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 microwave does instead is duty-cycle. 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. For sizing a circuit or an inverter, that means you should always 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 pulling up to 1,670W at the wall needs a unit rated comfortably above that, with headroom to spare rather than a station rated right at the edge. The BLUETTI Elite 100 V2 Portable Power Station and the EcoFlow DELTA 3 Classic Solar Generator both carry an AC output around 1,800W, which clears even the higher end of that range with margin; both list for $499 and $619 respectively and hold 1,024 Wh and 1,024 Wh of capacity, enough for many short cook cycles rather than one continuous run — a microwave is rarely on for more than a few minutes at a stretch. For a compact or dorm-style microwave in the 600-700W cooking range, a smaller unit like the Anker SOLIX C800 Portable Power Station – 768Wh at $314 with a 1,200W AC rating already has enough headroom.
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 catalogue, 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.
A gas microwave doesn’t exist, but the comparison still matters
Unlike a clothes dryer or a range, there’s no gas-heated version of a microwave to compare against — the whole appliance is electric by design, so the 120V figures above are the complete picture. That puts a microwave in the same bracket as a refrigerator or a window air conditioner rather than the 240V bracket reserved for dryers, ranges, and central air: it runs on a standard household circuit, just one that’s often asked to carry more current, by itself, than almost anything else plugged into an ordinary outlet.
How this page makes money. Some links here are affiliate links and we earn a commission if you buy through them — currently BLUETTI, ALLPOWERS, Mango Power, Renogy and MoonCool. Every other brand on this page is here because leaving it out would make the comparison useless to you, and we are paid nothing either way. Prices are each maker’s own list price at the time of writing and change often.