A misconception about microwaves is that they need around 1000W to actually do sonething, anything lower than 800 makes the waves completely ineffective. When you turn your microwave to 500W, what it actually does is lie to you while microwaving only half of the time instead by cycling on and off. You can usually hear this change in the sound it makes cause it will switch between the 1kW and the ventilator. 🙂