How much electricity can be harvested from water coming to a house?

Question

I realized we don't pay for water pressure when paying water utility bills, but only for the water itself. Can someone do the math and explain how much electricity can be generated with a hydroelectric generator to convert the high pressure water from the utility company coming into a home to low pressure that is still strong enough to have water flow normally in the house?Are there times of day that water pressure is even higher and more electricity can be extracted?Is the cost of extra water consumed for electricity production offset by the amount of electricity generated?

PaulHoule · Accepted Answer

It takes a lot of water to hold a little energy.

A cubic meter of water (1000 liters) weighs a metric ton, that is, 1000 kg.

If that fell 100 meters (a little more than 300 feet) that is

   10 m/s^2 * 1000 kg * 100 meter

or 10^6 J. That would generate 1kw of electricity for 1000 seconds. (Enough to bake 5 potatoes in the Microwave.)

That's a substantial amount of energy but it is a huge amount of water and it is a equivalent to a pressure of 10 atmospheres which would have blown up your plumbing!