When natural gas is burned, 10% of the energy is lost because the hydrogen in the fuel combines with the oxygen in the combustion air to form water vapor. When this water vapor is condensed, the latent heat, recovered at 980 Btu per pound (544.88Kcal/kg), will save one cubic foot (.28 cubic metres) of natural gas.

Given that 12% by weight of exhaust gas (at 15% excess air) is water, significant energy savings can be achieved through the recovery and use of latent heat. Moreover , every cubic foot of gas saved eliminates one cubic foot of carbon dioxide (CO2) emitted to the atmosphere.