A New Era in Home-Owner Hydro

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That said, a 400-watt system would typically cost $4,000 to $6,000, broken out like this: turbine, $700-1,000; batteries, $800-1,600; solidstate inverter and load controller, $1,200-2,000; transmission line and other electrical equipment, $500- 1,000. To this, add the price of penstock pipe (in some systems, the largest single cost) and of the intake, powerhouse, and labor.

Once you've bought a system, "fuel" is free. Since hydro systems are very reliable, annual maintenance costs should be $100 or less. But plan on replacing the batteries every decade or so.

Smaller systems are less expensive. A weekend cabin setup might run $800 to $1,500. And if you already own a wind power or PV system, adding a hydro turbine to help charge your batteries can cost as little as $400.

So far we've been talking about DC or "battery-based" systems, where alternating current is supplied by an inverter. But if you are blessed with water—say, 10 times more than you need for a DC system—you may be able to dispense with the inverter and generate AC directly.

AC Systems

Nine years ago, David Scott, a teacher who lives six miles off the grid near Gypsum, Colorado, got tired of trudging through the snow each morning to start a propane generator. Back then, his family was using 6,000 gallons of propane each winter to provide heat, hot water, and electricity to the three buildings on their property. Energy costs were eating them alive.

One summer Scott installed a hydro system. It wasn't cheap. Expenses—not including his time or use of a friend's backhoe—were $14,000, half of it for 4,000 feet of 8" pipe. By the end of August, though, Scott was the proud owner of a 35,000-watt (35-kilowatt or 35-kW), hydro system that, in his words, "sounds like a Boeing 747 when you turn it on:" (It ought to: Water enters his turbine at 98 mph.)

This system generates a staggering amount of electricity, whose retail value is about $21,000 a year. Since there's no utility to sell it to, Scott uses it to light and heat his house, a guest house, and a 1,600-ftz apartment. The surplus goes through a transformer and then to a neighbor, who uses it to heat and power his house.

Although Scott's AC system is much larger than most, it illustrates the possibilities. Over an eight-year span, it's been shut down four times for routine maintenance. And with a useful life of 50 years or more, it's already paid for itself many times over.

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