At maximum load auxiliaries only account for a small share of the total energy consumption for traction. For this reason, the effect of demand-operated ventilation is rather small in high-speed trains.

However, if low-load operation is significant in operation scheme, not demand-operated ventilation contributes substantially to energy demand.

Figure 1 shows the relation between tractive power and the auxiliary power expressed as a percentage.

Figure 1: Relationship expressed in percentage terms between the auxiliary power and real-time tractive power using the example of a 5 MW traction unit.

Source: IZT, data from Slattenschek 2000

Locomotives fitted with two-speed ventilation are mostly operated at the higher ventilation speed, which in low-load operation leads to much higher energy demand for ventilation than actually needed.

For example, the Re 6/6 on the Swiss Gotthard consumes about 10% of its total energy demand for traction only for ventilation.

The annual energy savings per locomotive are given by SBB as 50-135 MWh / a. As soon as all locomotives are equipped, this may sum up to 1,7% of the entire power consumption of public transportation in Switzerland.

A similar project conducted in Russia yielded energy savings about 4-8% in freight trains (depending on train mass and track profile)