A power estimation method is implemented in a three-phase electricity meter, and includes the steps of: detecting a fraud falsifying a first voltage measurement on a first phase; acquiring a second voltage measurement on a second phase, the second voltage measurement not being falsified by the fraud; estimating a first phase shift between the first phase voltage and a first phase current, by using a first phase shift estimation between the first phase voltage and the second phase voltage; estimating at least one first electrical power consumed on the first phase from a first current measurement on the first phase, of the second voltage measurement, and of the first phase shift.