Commercial microwaves come in a variety of wattages and this determines the speed of the microwave. The entry level is 1000 watt, going up to 1100 watt, 1500 watt and 1800 watt. The other main option is whether you have manual control or push button programmeable oven.  If you are purchasing a microwave you should consider buying a cavity liner which slides inside the machine, protects against splashes and spillages and can be washed or put in the dishwasher at the end of the day for cleaning. This will keep the chamber clean and extend the life of your microwave.