An energy conversion system includes an energy converter, a cold generator, and a liquid water obtainer. The energy converter is configured to convert energy of a source from one form to another form and generate heat and water vapor. The cold generator is configured to generate cold using the heat generated by the energy converter. The liquid water obtainer is configured to condense the water vapor using the cold to obtain liquid water. Accordingly, the water vapor generated from the energy converter can be cooled efficiently. Therefore, efficiency in obtaining the liquid water can be improved compared with a case where the water vapor is cooled by open air.