A self-compensating, energy saving heat transfer unit to provide an efficient means to transfer energy from steam to water in a central heating system. The steam enters a mixing chamber and creates a negative pressure environment. Water in a backwater pipe, which is at a lower temperature and pressure, is absorbed into the mixing chamber where energy is passed from the steam to the water. The water then leaves the first mixing chamber and enters a second mixing chamber where compensation water is added to make up for the possible loss of water that may occur in the central heating system. The heated water then exits the heat transfer unit and goes back into the central heating system. After being cooled in the central heating system, the water then reenters the heat transfer unit at the backwater pipe and continues the cycle over again.