Because seawater is much denser than air, ocean currents carry more energy than air currents. For example, a 15-meter (49.2 feet) tidal turbine can generate as much energy as a 60-meter (197 feet) diameter wind turbine. However, due to the cyclical nature of tides, tidal power technologies can only produce power for 6 to 12 hours a day. This means that tidal power must be paired with other power to provide uninterrupted electric service.