Most hydraulic tools used at a jobsite require a self-contained hydraulic power unit that is powered by a diesel or gasoline engine or an electric motor. When purchasing a hydraulic power unit, a number of factors must be considered.: * Determine which tools will be run off the unit. Each tool requires a specific flow and pressure of hydraulic fluid for proper operation. If you will be operating tools with different power needs, base your decision on the tool with the highest power requirements. * Determine how important size and maneuverability are to your operations. Look for the unit that will most efficiently serve you needs, not necessarily the largest or most powerful one. * Consider the possible running time you would like to obtain from the hydraulic power unit. The fuel capacity will affect the amount of continuous operating time possible. * Decide if you want a hydraulic power unit that has a water pump or water coolant attached.