[Delphinus]

Ineresting idea. The force of the water falling into the sump could turn a small turbine, which could be used to charge a battery which could in turn be used to power something in the event of a power failure. You wouldn't really recover energy in the form of lowering your ongoing costs - but you would be charging that battery without plugging in a new item into the wall.

Don't know how it is out your way but Calgary requires a building permit if you want to install panels on your roof. There is talk about loosening this requirement some in the near future to encourage more green thinking. Sadly the cost of good solar panels is huge and indeed you'll see a payback eventually, but it's in the 10 to 20 year mark. Wish they weren't quite that expensive.

I noticed a HUGE percentage of houses in Hawaii (well, at least Maui, when I was there a few years ago) had solar panels on the roof. So in some places this idea is catching on for sure.

If water still flows during a power failure, there could be two possibilities. One, your utility has its own power supply, or two, they use elevated water tanks to generate the hydrostatic pressure. Not really sure what Lower Mainland uses but a lot of west coast municipalities in the U.S. use the water tanks idea. Calgary does not - we pump direct into distribution. If there was zero power then there would be no water coming out of taps as well, given enough time to bleed the pressure down in the lines. I would think, anyhow.