The invention relates to an elevator installation and also to a method for controlling elevators. In the method a run plan is formed for driving elevator cars on the basis of service requests, the elevator cars are driven according to the run plan, by supplying electric power via the electricity distribution network of the building to a hoisting machine driving an elevator car, and also by supplying electric power from a hoisting machine braking an elevator car back to the electricity distribution network of the building, alternatives for a run plan are formed for driving elevator cars on the basis of service requests, the electric power which the hoisting machines need for implementing the aforementioned alternatives is determined, and also a run plan is selected for use from the plurality of different alternatives, when implementing which run plan the electric powers of the hoisting machines, when summed together, smooth the power variation occurring in the electricity supply of the building.