The invention relates to an electrical power system for operating elevators. The electrical power system includes: an electricity distribution network of a building, which includes an interface to a public electricity network; a plurality of hoisting machines of an elevator, each of which hoisting machines of an elevator is equipped to move an elevator car in an elevator hoistway; and also a power supply system, which includes an interface to the aforementioned hoisting machines of the elevator, and which power supply system includes an interface to the electricity distribution network of the building, for supplying power between the hoisting machines of the elevator and the electricity distribution network of the building.