E-RS Retrofit Solution

The intelligent retrofit for the efficient operation of shaft generators

These days, slow steaming is highly important – even for special ships. But this operating mode isn’t always efficient for on-board operation: The significantly reduced speed of the main engine and simultaneous operation of the shaft generator at a constant speed and high efficiency work against each other.

E-MS created a solution for this problem: With the intelligent E-RS retrofit solution, we make it possible to operate conventional shaft generators on board existing ships efficiently again, even at low speeds.

The advantages at a glance

  • Efficient shaft generator operation, even at variable speeds, in slow steaming operation
  • Intelligent management of the electrical power supply
  • Fuel savings of up to 15%
  • Maximum flexibility in all operating modes
  • Low investment costs, return of investment
  • Easy implementation without off-hire times
  • Only minimal modifications to existing switchboard systems and main engine control


If the on-board network of a diesel, mechanically driven ship is supplied by a shaft generator (PTO), it must usually be switched off when travelling slowly. The auxiliary generator sets are then responsible for power generation. It is significantly more expensive to operate auxiliary generator sets than the main engine. The auxiliary gensets use diesel (MDO) instead of heavy fuel oil (HFO), which results in increased maintenance costs.

E-RS now allows even on board of existing ships to operate in shaft generator mode at nearly any time and under any operating conditions, so that they can travel with maximum efficiency.


In order to make this possible, we use an innovative converter system, which ensures that power is supplied by the shaft generator even at variable speeds, without the auxiliary gensets having to run.
E-RS also allows parallel operation of the shaft generator and auxiliary gensets. For this purpose, a bypass switch can be added to the converter system, so that conventional operating modes on board can be retained and used as before.


The investment in E-RS is very manageable. The return-on-investment (RoI) essentially depends on the duration and speed of the slow steaming operation, as well as the costs of the different fuel qualities for the main and auxiliary engines. Our calculations for existing ships indicated that only 1-2 years would be required for the RoI. So it’s an investment that pays off – even for older ships!