"Peak Horsepower" (PHP) is a term used in the wet-dry vacuum industry for consumer comparison purposes. It does not denote the operational horsepower of a wet-dry vacuum but rather the horsepower output of a motor, including the motor’s inertial contribution, achieved in laboratory testing. In actual use, Shop-Vac motors do not operate at the peak horsepower shown.
CFM (Cubic Feet Per Minute)
CFM is a measure of the quantity of air moved by the vacuum motor at a particular system load, such as 2-1/2" orifice. Your actual system load is determined by the type, size and length of the hose used, the accessory tool used and the filter system used. A dirty filter system can drastically affect the suction and air flow. The filters need to be cleaned regularly and replaced as necessary to avoid reduced suction and air flow.
SP (Sealed Pressure)
Suction pressure represents how far up a glass tube a vacuum motor will lift a column of water. This function is measured in inches. Maximum suction pressure or sealed water lift is obtained at zero air flow. Suction pressure decreases as air flow increases.
Vacuum performance or air power is the rate of work performed by a vacuum cleaner. Air power is a function of suction and air flow at an operating point. Air power is reduced by dirty filters, leaks and attachments used.