Carpet cleaning has evolved and equipment has gotten more powerful. Not all carpet cleaning technicians are the same and neither is the equipment used. A truck-mounted system uses a separate engine inside of the van and hoses are connected to the truck mount steam engine and then taken into your house. The truck mount has its own power and fuel supply and does not need electricity to operate. It usually requires a water source whether an on-board water tank or a hook up to a water source via a garden hose.
The water is taken into the truck, on-demand, and the exhaust of the truck as well as engine heat is used to heat the water before it travels down the hose to clean your carpet. Some truck mounts are powerful and can heat the water, others sadly cannot. The same engine also supplies the powerful vacuum used to extract the hot water back out from your carpet, which contains dirt and soil to a waste tank that is also on the truck. There are literally thousands of models ranging from home-made units for $1,500 and can go all the way up to $40,000. So there is a great range of technical experience with the carpet cleaning technician as well as the limitless range of equipment that can be deployed to steam clean carpets.
Truck mounts can have a huge range in price and power. The engine power is in horsepower, ranging from 16hp on the low, which are tractor type engines, and on the high end, 68-70 horsepower, which is typically 4-cylinder water-cooled car engines. The suction is related to the size of the blower, the biggest being a Number 5 blower. The larger the blower, the more negative air, or suction it can generate which in turn determines how much water is extracted out of your carpets, which affects dry time. The other factor is heat, meaning what temperature the machine can clean at and how long can it maintain that temperature under constant use. A standard sort of minimum temperature would be 180 degrees Fahrenheit. Again, cheaper and less powerful or badly maintained machines will clean at a much lower temperature. The hotter the steam, the better the carpet clean. The faster the dry time and also less residue.