Compared with traction elevators, hydraulic elevators are less mechanically complex, making them ideal for low-rise, low-traffic installations. Because the pump works on gravity, pushing the car and its passenger up, they are less energy efficient. This energy is lost when the car falls on its own weight. Too high a current when the pump is started can also put higher demands on the building’s electrical system. If the lift cylinder leak enters the groove, there are also environmental problems.