What size inverter to run a microwave?
A microwave drawing 1,200 W from the outlet needs about a 1,500 W inverter (1,200 W plus 25% headroom). On a 12 V battery it pulls about 111.1 A while it runs.
How to work it out
- Running: 1,200 W × (1 + 25%) = 1,500 W → 1,500 W inverter
- Surge: 1,200 W running + biggest start-up extra = 1,200 W
- Battery current: 1,200 W ÷ 90% ÷ 12 V = 111.1 A (138.9 A at 1,500 W)
The number on the microwave’s box is usually its cooking power; what it draws from the outlet is higher and is printed on the label inside the door or on the back. Size the inverter on that input figure. Champion’s chart lists microwaves at 600–1,200 running watts and no extra starting watts.
Adjust for your project
More options: Headroom · Inverter eff.
- Running watts, all together
- 1,200 W
- Continuous rating with headroom
- 1,500 W
- Surge (peak) rating needed
- 1,200 W
- Battery current at your load
- 111.1 A
- Battery current at the inverter’s full rating
- 138.9 A
- For motors, compressors, CPAP machines and electronics, choose a pure sine wave inverter.
Battery current at other battery voltages
| Battery voltage | Battery current at your load | Battery current at the inverter’s full rating |
|---|---|---|
| 12 V | 111.1 A | 138.9 A |
| 24 V | 55.6 A | 69.4 A |
| 48 V | 27.8 A | 34.7 A |
What to know about running a microwave on an inverter
- 700 W, 900 W, 1,000 W microwaves. Those are usually cooking power. If the label says 1,000 W input, about 1,250 W with headroom — a 1,500 W inverter. A 700 W-cooking microwave still draws more than 700 W from the outlet, so read the label.
- Short runs, big current. Five minutes at 1,200 W takes about 111 Wh from the battery — little energy, but over 110 A at 12 V. The battery must be able to deliver it: Victron recommends no more than 100 A continuous from its 12.8 V 100 Ah LiFePO4.
- Pure sine. Microwaves on modified-sine inverters can run hot, loud and slow.
- Nothing else at the same time. If the coffee maker or kettle might run alongside, add it to the list — that is how a 1,500 W inverter becomes a 3,000 W one.
The battery that can carry it is on what size battery bank for a 2000W inverter. The DC current at 1,000 W is on how many amps is 1000 watts at 12 volts, and the runtime on how long a 100Ah battery lasts with a 1000W inverter.
Different size? Use the full Inverter Size Calculator.
What you’ll need
- Pure sine wave inverter, 2000–3000 WPremium price
For microwaves, coffee makers and power tools. At 12 V these draw hundreds of amps, so the battery and cabling matter as much as the inverter.
See options on Amazon (opens in a new tab) - 12 V 100 Ah LiFePO4 batteryPremium price
About 1.28 kWh rated in a box roughly the size of a group 24–31 lead-acid battery at around half the weight. Check the BMS discharge limit and whether it can charge below freezing.
See options on Amazon (opens in a new tab) - DC clamp meterMid-range price
Clamps around one cable to read DC amps without breaking the circuit — checks what an inverter or fridge actually draws from the battery. Make sure it says DC; many cheap clamps read AC only.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
What size inverter to run a 1000 W microwave?
About a 1,500 W inverter, drawing 92.6 A from a 12 V battery.
What size inverter to run a microwave and a fridge?
About 2,000 W continuous, with a surge rating of at least 2,400 W.
What size inverter to run a microwave on 24 V?
Still a 1,500 W inverter — the AC side doesn’t change — but it pulls only 55.6 A from a 24 V battery.
Other common sizes
- What size inverter for a refrigerator — 600 W or more, with a 1,200 W surge rating
- What size inverter to run a CPAP — 150 W pure sine (300 W with a heated humidifier)
- How many amps a 1000 watt inverter draws — 92.6 A
- How many amps a 2000 watt inverter draws — 185.2 A
Sources
- Champion Power Equipment — Generator Wattage Chart (opens in a new tab) — Typical running and starting watts for household, RV and job-site appliances (a manufacturer’s planning chart — your nameplate wins).
- Virginia Cooperative Extension, BSE-301: Estimating Appliance and Home Electronic Energy Use (2020) (opens in a new tab) — Wattage × hours ÷ 1,000 = kWh per day; watts = amps × volts when only amps are listed; a refrigerator runs at full wattage about a third of the time; typical nameplate wattages.
- Victron Energy — Energy Unlimited (book) (opens in a new tab) — Lead-acid charge efficiency 80–95% (85% suggested as a starting value); battery energy efficiency about 75% for full cycles, about 89% in partial state of charge; inverter efficiencies above 90%.
- Victron Energy — Lithium Battery Smart manual, technical data (opens in a new tab) — LiFePO4 12.8 V: cycle life 2,500 at 80% DoD, 3,000 at 70%, 5,000 at 50% (to 80% of capacity); 92% round-trip efficiency; 12.8 V 100 Ah: recommended continuous discharge ≤100 A (1C), maximum 200 A; capacity about 20% lower at 0 °C; charge only between +5 °C and +50 °C.
- ENERGY STAR — Certified Televisions data set (on-mode power) (opens in a new tab) — Certified models, on-mode watts, retrieved October 2026: 32 in about 27–36 W; 43 in about 45–78 W; 50 in about 61–90 W; 55 in about 64–114 W; 65 in about 85–135 W; 75 in about 120–176 W.