To reduce uncertainty ascertain how long the washer would be used each week and how hard it would have to work. To have a washer working at full tilt all the time will not improve its longevity. It is also important to think about the kind of cleaning required is the dirt caked on? Do you want to clean large floor areas or smaller pieces of equipment. Do you need a hot or cold water version?
Industrial Hard Floor Cleaning Machines
Fuel Tank/Fuel Consumption (Hot Water Versions)