Evaluating a Potential hydro Site

To build a microhydropower system, you need access to flowing water on your property. A sufficient quantity of falling water must be available, which usually, but not always, means that hilly or mountainous sites are best. Other considerations for a potential microhydropower site include its power output, economics, permits, and water rights.

Power Output

To see if a microhydropower system would be feasible, you'll want to determine the amount of power that you can obtain from the flowing water on your site. This involves determining these two things:
   Head-the vertical distance the water falls 
   Flow-the quantity of water falling

Once you've calculated the head and flow, then you can use a simple equation to estimate the power output for a system with 53% efficiency, which is representative of most microhydropower systems.

Simply multiply net head (the vertical distance available after subtracting losses from pipe friction) by flow (use U.S. gallons per minute) divided by 10. That will give you the system's output in watts (W). The equation looks this:

[net head (feet) × flow (gpm)] ÷ 10 = W

To help make a microhydropower system more feasible, it's a good idea to make every effort to reduce your electricty usage.

Economics

If you determine from your estimated power output that a microhydropower system would be feasible, then you can determine whether it economically makes sense.

Add up all the estimated costs of developing and maintaining the site over the expected life of your equipment, and divide the amount by the system's capacity in watts. This will tell you how much the system will cost in dollars per watt. Then you can compare that to the cost of utility-provided power or other alternative power sources.

Whatever the upfront costs, a hydroelectric system will typically last a long time and, in many cases, maintenance is not expensive. In addition, sometimes there are a variety of financial incentives available on the state, utility, and federal level for investments in renewable energy systems. They include income tax credits, property tax exemptions, state sales tax exemption, loan programs, and special grant programs, among others.

Permits and Water Rights

When deciding whether to install a microhydropower system on your property, you also want to know your local permit requirements and water rights.

Whether your system will be  grid -connected or stand alone will affect what requirements you must follow. If your microhydropower system will have minimal impact on the environment, and you aren't planning to sell power to utility, there's a good chance that the process you must go through to obtain a permit won't be too complex.

Locally, your first point of contact should be the county engineer. Your state energy office may be able to provide you with advice and assistance as well. 
You'll also need to determine how much water you can divert from your stream channel. Each state controls water rights; you may need a separate water right to produce power, even if you already have a water right for another use.