With the ever tightening of budgets and legislation, new vessel builds are facing tough times. The future maritime industry requires more efficient vessels to minimise ship operational costs with cleaner technologies that meet stringent environment regulations, reduce greenhouse gas emissions, specifically carbon emissions. Emissions reduction continues to be high on the agenda for the marine industry, it is responsible for about 2.5 percent of global greenhouse emissions1 and is under great pressure to reduce its environmental impact. With pressure comes the opportunity to incentivize innovation, developments and implementation of energy efficient measures, both design and operational. Naval propulsion systems are no different from other industries, and the industry is exploring ways to optimise propulsion and electrical power generation systems architecture for better performance and efficiency. Electric technology plays a leading role. The paper will: Provide a brief overview about the hybrid propulsion concept, with key electrical, mechanical qualities and issues. Describe different designs configurations and performances of hybrid propulsion systems from demonstrated and operational systems in the commercial and naval world. Cover the lessons learnt in technologies and controls used on such systems. Examine future architectures including energy storage and explore the benefits and the flexibility these can bringto the hybrid propulsion sphere.