Division Method 3: Calculation of a proxy based on measured efficiency

The operator determines amounts of net measurable heat based on the fuel input and the measured efficiency related to the heat production:

Where Q is the amount of heat expressed in TJ, η_H is the measured efficiency of heat production, E_IN is the energy input from fuels, AD_i are the annual activity data (i.e. quantities consumed) of fuels i, and NCV_i the net calorific values of fuels i.

The value of η_H is either measured by the operator over a reasonably long period, which sufficiently takes into account different load states of the installation or taken from the manufacturer's documentation. In that regard the specific part load curve is to be taken into account by using an annual load factor:

Where L_F is the load factor, E_IN the energy input as determined using Equation 6 over the calendar year, and E_Max  the maximum fuel input if the heat producing unit had been running at 100 % nominal load for the full calendar year.

The efficiency should be based on a situation in which all condensate is returned. A temperature of 90 °C should be assumed for the returned condensate.