Compared with the diffusion jet pump, the pumping capacity and the maximum outlet pressure of the oil diffusion pump are much lower, so the heating power of the pump is also lower. The boiler diameter of an oil diffusion pump is usually equal to (smaller than) the pump port diameter. The heat load of the oil diffusion pump boiler with a pumping speed greater than 500L/S does not exceed 2-2.5W/cm2.

In the oil diffusion pump, the power consumed by oil evaporation is usually 60%-70% of the total power, and the rest is the power to compensate for various heat losses. The heat loss in the diffusion pump mainly has the following aspects:
Heat conduction from the heater surface to the outside through the boiler wall (20%-25%);
Heat conduction along the pump wall from the hot boiler to the cold pump body (accounting for 10%-15%);
Radiation from the surface of the draft tube to the pump wall and heat conduction of the mixture of gas and steam from the draft tube to the pump wall (5%-10%).

If the results of the pump are better, the heat loss can be reduced to 10%-15% of the total power. For example, insulating pump heaters and boilers can significantly reduce heat loss. If a closed heater is used, there is no air layer between the bottom of the boiler and the heater, and the heating power can be well utilized.