The invention relates to a method for estimating the thermal behavior of a building for optimal heating control, comprising the steps of measuring the temperature outside the building with a first temperature sensor (40), measuring the power supplied internally to the building using a first set of adapted sensors (43) and measuring the external power supplies received by the building using a second set of adapted sensors (44) simulating the thermal behavior of the building using an electrical circuit model Equivalent of the RxCy network type, in which x and y are greater than or equal to 2, characterized in that it further comprises the step of measuring the internal temperature of the building, with a second temperature probe (42), the step of measuring the external temperature, the power supplied internally, the external supplies and the internal temperature, is operated for a defined period of time and with a pitch less than or equal to 10 minutes, The step of simulating the thermal behavior of the building with the aid of an equivalent electric circuit model of the RxCy network type is carried out with the aid of open-loop operating data of the outside temperature, of the power supplied internally, of the external supplies, as well as data recorded in a closed loop but exploited in an open loop of the indoor temperature, without modeling the regulation, and in that it further comprises the step of providing a resulting dynamic representation of the thermal behavior of the building. The invention also relates to a system for carrying out said method.