A system for analyzing an interior energy system including: at least one detachable sensor arranged to monitor a portion of the interior energy system; and an apparatus including a processor configured to receive data of a first parameter of the interior energy system from the at least one detachable sensor and determine a second parameter of the interior energy which is inferred on the basis of the received data of the first parameter; and determine a characteristic of the interior energy system from the determined second parameter. The system may provide analysis of the interior energy system and recommend improvements.