Method of estimating power output of heat exchangers in a heating system comprising a heat source arranged to heat a working fluid and to circulate said working fluid through a plurality of heat exchangers, said method comprising the steps of, at a plurality of predetermined times: - obtaining measurements of heating power P output by said heat source; - obtaining measurements of inlet temperature T in of said working fluid at an inlet of at least some of said of heat exchangers; - obtaining measurements of ambient temperature T amb of the surroundings of said heat exchangers; - calculating power P rad output by each of said heat exchangers individually, according to the equation P rad = Q N F T n where Q N is a nominal power coefficient of said individual heat exchanger, F is a characteristic function of temperature based upon at least said inlet temperature T in and said ambient temperature T amb measured at said individual heat exchanger, and n is a characteristic coefficient of said individual heat exchanger, wherein, during a training phase, said measurements are obtained during a predetermined training period and at predetermined times, said measurements being used to calculate said nominal power coefficient Q N for each heat individual exchanger by equating the sum of values of P rad for all of said heat exchangers with power P output by said heat source at corresponding times and determining the values of Q N for each individual heat exchanger, and wherein, in an operating phase, said calculation of the power output P rad of each of said individual heat exchanger is carried out based on said measurements and the nominal power coefficients Q N determined in said training phase. - obtaining measurements of heating power P output by said heat source; - obtaining measurements of inlet temperature T in of said working fluid at an inlet of at least some of said of heat exchangers; - obtaining measurements of ambient temperature T amb of the surroundings of said heat exchangers; - calculating power P rad output by each of said heat exchangers individually, according to the equation P rad = Q N F T n where Q N is a nominal power coefficient of said individual heat exchanger, F is a characteristic function of temperature based upon at least said inlet temperature T in and said ambient temperature T amb measured at said individual heat exchanger, and n is a characteristic coefficient of said individual heat exchanger, wherein, during a training phase, said measurements are obtained during a predetermined training period and at predetermined times, said measurements being used to calculate said nominal power coefficient Q N for each heat individual exchanger by equating the sum of values of P rad for all of said heat exchangers with power P output by said heat source at corresponding times and determining the values of Q N for each individual heat exchanger, and wherein, in an operating phase, said calculation of the power output P rad of each of said individual heat exchanger is carried out based on said measurements and the nominal power coefficients Q N determined in said training phase. where Q N is a nominal power coefficient of said individual heat exchanger, F is a characteristic function of temperature based upon at least said inlet temperature T in and said ambient temperature T amb measured at said individual heat exchanger, and n is a characteristic coefficient of said individual heat exchanger, wherein, during a training phase, said measurements are obtained during a predetermined training period and at predetermined times, said measurements being used to calculate said nominal power coefficient Q N for each heat individual exchanger by equating the sum of values of P rad for all of said heat exchangers with power P output by said heat source at corresponding times and determining the values of Q N for each individual heat exchanger, and wherein, in an operating phase, said calculation of the power output P rad of each of said individual heat exchanger is carried out based on said measurements and the nominal power coefficients Q N determined in said training phase.