A countertop microwave uses the same amount of power as a similar built-in model. Whether a microwave is mounted or freestanding does not affect the energy consumption of the appliance. Generally, larger microwaves use more electricity than compact models.
Microwaves typically use between 600 and 1,500 watts, depending on how frequently the unit is operated. The average contemporary model consumes approximately 1,200 watts during use. The average power use is between 500 and 800 watts for compact models and 850 to 1,800 watts for regular and large models.
Besides built-in and countertop styles, microwaves can be mounted over or built into a range. The latter is a drawer-style unit, at an easier height for children and short people to use.
The standby mode of a microwave oven, where the unit is powered and idle, consumes more energy than actual operation of the appliance, which typically uses 100 times the power. The website Energy Use Calculator estimates that standby mode on microwaves consumes 2 to 7 watts of energy. The article notes, though, that microwaves are in standby approximately 99 percent of the time. Attempts to reduce power consumption on the part of manufacturers involve engineering "switch mode" power supplies into units like microwaves.