Microwaves look powerful on the nameplate and cheap on the bill because they run for minutes, not hours. A typical household unit draws about 1,000–1,500 watts while heating. Reheating leftovers for 3 minutes is a small slice of a kilowatt-hour.
The cooking-power number on the box (e.g. 1,000 watts cooking) is not always the wall draw; wall draw is higher. Whatt wants wall watts. If you only know cooking watts, the estimate is still in the right neighborhood for a short use.
Leaving it on the clock all day is standby — usually just a few watts. The heat button is the line that matters.
Price the minutes you actually run it. A 10-minute “baked potato” program is a different habit from a 90-second reheat.
At 18.8¢ per kWh, 1,200 watts for 5 minutes is 0.1 kWh — about 0.02. You would need many of those to match one dryer load. That is the point of putting it on its own card: so the big loads stay obvious.
Clock vs cook
The clock is standby. Price the minutes the magnetron is on. A baked-potato program is a different habit from a 90-second reheat.
Related
Usage estimate only — not a utility bill, load calc, or advice.