Apparatus for monitoring and analysing the performance of a heating and/or cooling system for a space within a building. The apparatus comprises a processing arrangement and an electronic memory, wherein the processing arrangement is configured to receive temperature signals representing temperature measurements from a temperature sensor within the space over a monitored period of time, to process the temperature signals so as to generate output data which attributes a proportion of the energy consumption of the heating and/or cooling system to a specified energy output, and to transmit the output data to the electronic memory for retrieval by a user. Corresponding monitoring and analysis methods are also described.