Professional machines range from portable machines, which use electricity to heat the water and power the water pump and vacuum motors, to larger truck mounted machines. Truck mounts are normally stationary gas/diesel engine or PTO powered machines installed in a van or truck. The portable machine is able to access difficult to reach buildings and high story floors, while the truck mount's advantages are its power to heat the water and power of vacuum and faster cleaning and drying times. DIY and rental machines use some of the technology from the professional systems, but with less power and usually without an element to heat water (filling the unit with hot water is advised) the results are limited, these units are not typically called HWE systems.[3]