Abstract: A method of inference of appliance usage from a point measurement on a supply line, said supply line being common to multiple appliances and/or components of appliances comprises the steps of: obtaining data from said measurement point; sampling power and reactive power at intervals substantially throughout periods of operation of said appliances or components of appliances corresponding to appliances or components of appliances being in ON and/or OFF modes of use; identifying characteristics of events by assessing power and reactive power change during an event; and by assessing one or more additional characteristics derivable from said power and reactive power to characterise an appliance; grouping events and/or cycles of events into clusters of similar characteristics; and inferring appliance usage based on said grouping.