Ten minutes of cooking is a small amp-hour number. The inverter that can actually run the microwave sets the bank.
Direct answer: Honda lists a 1,000 W cooking microwave at 1,500 W running and 1,500 W starting, so the inverter needs at least 1,500 W continuous (Honda wattage guide). A 2,000 W inverter, which is above that draw, needs at least 200 Ah of battery under the 100 amp-hours per 1,000 watts rule (Battle Born inverter guide). Ten minutes at 1,500 W is 250 watt-hours, or 20.8 Ah at 12 V, so the inverter rule is the number that sizes the bank (Battle Born battery-bank guide).
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Honda separates cooking watts from the watts the inverter sees, and lists the same number for running and starting. Champion publishes a single 600–1,200 W range.
Ten minutes is the example length on this page. Champion's notes give 600–1,200 W as one range, without a separate start column.
How to size it
Use the electrical watts, not the cooking-power number on the door. Honda's 1,000 W cooking model is 1,500 W running and 1,500 W starting. The 800 W cooking model is 1,300 W both columns. The 650 W cooking model is 1,000 W both columns (Honda wattage guide).
The inverter's continuous rating has to be at least those running watts, so the largest Honda case needs at least 1,500 W continuous, and the surge rating has to clear the same 1,500 W because start and run match (Battle Born inverter guide; Honda wattage guide).
For a 10-minute example, watt-hours are watts × 10 ÷ 60. The 1,500 W draw is 250 Wh, and 250 ÷ 12 = 20.8 Ah. The 1,300 W draw is 216.7 Wh and 18.1 Ah. The 1,000 W draw is 166.7 Wh and 13.9 Ah (Battle Born battery-bank guide; Honda wattage guide).
Champion lists a microwave at 600–1,200 W. On the same 10 minutes that is 100–200 Wh, or 8.3–16.7 Ah at 12 V (Champion wattage chart). An inverter still has to cover whichever end of that range you actually have.
Current decides the parallel count. 1,500 ÷ 12 = 125 A, over one battery's 100 A continuous rating. Two batteries in parallel are rated 200 A continuous, and 2,000 W at full inverter load is 2,000 ÷ 12 = 166.7 A, still under that 200 A (Battle Born 100 Ah manual). Larger inverters are also recommended with a minimum of two batteries (Battle Born inverter guide).
The 10-minute energy is why people undersize. 20.8 Ah of cooking does not replace the 200 Ah inverter rule. The guide's reason for the amp-hour rule is voltage drop, reduced performance, and shutdowns when the bank is too small for the inverter (Battle Born inverter guide).
Lead-acid at about 50% depth of discharge doubles nameplate. The inverter rule becomes about 400 Ah of lead-acid. The 10-minute slice doubles 250 ÷ 12 by the same ratio: 500 ÷ 12 = 41.7 Ah of lead-acid nameplate for those 10 minutes only (Battle Born chemistry guide). Keep the 400 Ah figure if the inverter is 2,000 W.
A microwave is a short spike on top of a daily load. Put the all-day loads into the battery bank calculator.
Use an inverter of at least 1,500 W continuous for Honda's 1,000 W cooking microwave, which draws 1,500 W running and starting. On a 2,000 W inverter the Battle Born inverter guide calls for at least 200 Ah (Honda wattage guide).
How many amp-hours is 10 minutes of microwave use?
Why is the bank 200 Ah if 10 minutes is only a small slice?
The 10-minute figure is 20.8 Ah. The binding figure is the inverter: 2,000 W needs at least 200 Ah so the bank can support the inverter (Battle Born inverter guide).
How many batteries keep the draw under 100 amps?
Two. 1,500 ÷ 12 = 125 amps, over 100 amps continuous and under the 200 amp continuous rating of two batteries in parallel (Battle Born 100 Ah manual).