How much weight is required to produce a watt of power is one measure of the efficiency of a portable alternative energy system. Micro hydropower generators, often submerged underneath boats, are lighter than micro wind generators. For example, Ampair, a company based in England, offers a 100-watt micro hydropower generator and a 100-watt micro wind generator. Calculations reveal that the micro hydropower watt to weight ratio is twice that of the micro wind generator: 6.6 watts per kilogram compared to 3.3 kilowatts per kilogram.
According to the United States Department of the Interior, in a report titled Reclamation: Managing Water in the West, the cost per kilowatt hour for a hydropower plant is less than a penny. Another estimate from the Wisconsin Valley Improvement Company is 0.08 cents per kilowatt hour.
This is much less than current costs to produce wind energy. The United States Energy Information Administration estimates that wind generation production costs range between 3.5 cents to 5 cents per kilowatt hour. GE Energy, a major producer of wind generators, estimates that wind energy production costs are about 3.5 cents to 4 cents per kilowatt hour and declining.
Because dams are often needed for flood control, hydropower allows for a way to help fund the building of the dam and reservoir. Revenue from electricity generated from the hydropower plant can be used to offset the cost of building the dam.
Additionally, because many dams in the United States are not as yet retrofitted, significant amounts of hydropower could be generated without building new dams. With the advent of much smaller micro hydropower generators, smaller existing dams and rivers could be used for the generation of low-cost hydroelectrical energy,
A hydropower plant is more reliable than wind energy. That's because the water in a lake or flowing down a major river or stream, will provide a consistent flow rate, usually day after day and night after night. However, this cannot be said for the wind. Global warming effects have resulted in different weather and wind patterns. And not even the weatherman will guarantee how hard and how long the wind will blow tomorrow.