It varies from MW to MW unit. Look at the input wattage, not the MW's output wattage rating. I've seen 800 watt output units with as high input wattage levels as some more expensive and fancier 1200 watt output rated MW's.
Not sure why there is such a difference in efficiency ( ie the output wattage divided by input wattage)?
My bud's unit will only start his large MW whenever it's below approx. 60F (15C) outside temp. He learned last summer on a hot day it will NOT do it when it's hot mid day temperature outside.
I've not tried mine to that level of testing yet.
