The 16 hp unit is used for people that do not want to hook to a vehicle gas tap kit. The 20 hp unit will require hooking to a boat or marine fuel tank or vehicle gas tap kit. The 20 hp is more popular with customer that clean more air duct jobs (because of the higher CFM's) and for use cleaning tile (twin cylinder produces more BTU's of heat for higher water flows). The added BTU's of heat means the 20 hp truckmount will get hotter faster.
Now the 16 hp unit will clean air duct and tile cleaning, it will be just a little slower.
16 hp will operate 300 ft of hoses
20 hp will operate 350 ft of hoses
Both machines are capable of running power wands.

-Truckmount 13Hp Lifan 33 Blower 2000psi All Stainless Hose & Wand Steam Brite Steamer Carpet Extractor Tile Cleaning Machine, TM1333L, , by Steambrite MFG, THE LOWEST PRICED 13 HP ALL STAINLESS CONSTRUCTION, THERMOSTATIC HEAT CONTROLLED TRUCK MOUN...

..Steambrite MFG 20 Hp Stainless TruckMount Carpet Cleaning Machine Kohler Engine 36 Tuthill Blower Arimitsu Pump w hoses and wand, TM2036, -Steambrite MFG Truckmounts, Truckmounts by Brand, Equipment Carpet Cleaning Machines, by Steambrite MFG, INCRED...

Question: What is a carpet cleaning machine 'Power Wand'? Answer: A power wand refers to any carpet cleaning wand that operates on the end of a vacuum and solution