Small ones cost about the same as erecting a windmill without the added cost of having to be rebuilt every 10 years like a windmill. 70+ years looks to be about the average lifespan of a well maintained hydro generator.
Even a small single generator dam with 10 feet of head produces the same amount of energy as windmill can produce at peak efficiency. A dam on the other hand produces that electricity all day every day 365 days per year. Larger dams produce more electricity than entire wind farms. The cost of hydro averages about 0.7¢ per kwh which is really about as good as it gets. Hydro also has the added benefit of actually producing wealth in the form of high dollar lakefront property, water recreation and fishing revenues.
The drawback of hydro is that it isn’t portable but much of the country already has it available but unused. Where it isn’t available coal and gas will still be available.
Overall I’d say we’re probably spending more on windmills right now than hydro would cost in the long term but wind mills are going to continue to cost year after year with ever growing costs.
There’s a reason the greenies are hot to tear out all the dams in the country.
Sounds like a lot of these dams are quite small - merely enough juice for a single home or farm.
10 feet of head only tells us the drop; not the volume.
I have 12’ of drop across my property; but only about 1 foot is usable; flowing from the Lake of Death...