Electro-Turbo-Compounding (ETC) is a system whereby energy contained in the hot gas of a diesel-engine exhaust is partially recovered through its conversion via a high-speed gas turbine driven alternator into electrical energy. ETC makes a diesel-engine system work more cleanly and effectively thereby improving power density and fuel efficiency. The technology is equally suited to new-build and retrofit applications. Applications to date have been extensive in the 150 kW – 2 MW range and the 10 MW – 20 MW but almost exclusive to shore-based power stations across the world. This paper reports on the progress of an Innovate UK funded project (2015-18) to develop ‘marinised’ units with partners UCL, Bowman Power Group Ltd., Lloyd’s Register and Rolls Royce PLC. With an expectation on the shipping industry (including naval ships) to reduce their carbon footprint the ETC is suitable for marine engineering application in those ships not easily able to use the conventional Rankine Cycle exhaust gas waste heat recovery system. The paper discussions include the design, modelling and practical testing approaches, results on performance for various arrangements for propulsion and electrical power, and importantly the integration challenge to ensure NOx Compliance and Certification. Within the paper discussion is also made about the financial aspects for propulsion and electric generation applications. The operating profile of different vessels gives different paybacks which are particularly favourable at times of rising fuel prices.