The overall project balance is calculated with the following conventions. In each process, the energy type allows one to distinguish between purchased energy, useful energy, and other energy. The purchased energy generally represents the sum of all the energies that must be supplied to the cycle from outside. The useful energy is the net energy output of the cycle, e.g. the algebraic sum of the energies internally produced and spent.

These two energy types are those that appear in the definition of the cycle effectiveness : eta = |useful energy| /|purchased energy |

For example, in a Rankine cycle, the purchased energy is the heat supplied to the boiler and the useful energy is the net work output, i.e. the work produced by the turbine minus the work provided to the pump. The other energy is that used by the condenser. For a refrigeration cycle, the purchased energy is the input power of the compressor, the useful energy is the refrigeration effect (heat removed at the evaporator level), and the other energy is that removed at the desuperheater and condenser levels.