A power analyser for analysing an electrical supply to a load, comprising: a processor; an analogue signal module interfaced with the processor, wherein the analogue signal module is configured to: make analogue signal measurements of the electrical supply, and provide raw analogue data corresponding to said measurements to the processor; and wherein the processor is configured to: access a model suitable for, or associated with, the electrical supply and/or the load, and generate a modified electrical supply estimate in accordance with the model and the raw analogue data.