As an example, Solar Electric (photovoltaics) gets only around 1/3 as much useful power out of a given amount of surface area as Solar Hot Water Heating does. But Solar Hot Water Heating itself can cost you around $7000 to save only $250/year (for the best and most efficient system available for the Seattle area). So there is a high cost to idealism in those green energy technologies.
I have been searching for economically justifiable green energy applications. Here are some. But the best is the Drain Water Heat Exchanger.
Why am I excited about drainwater heat exchangers?
Just check this out. 70% of the heat in your shower water and dishwasher water just go down the drain. You know this; your used hot water goes into the drain still warm, right (105 degrees F. at the showerhead, 95 degrees F at the drain)? Most of that heat just warms up the dirt surrounding the next hundred feet of sewer pipes in the street by your home.
You're paying a lot of money to heat up that dirt. But you don't have to, with a DWHE.
So at a restaurant or laundry where they use a lot of hot water, which is all just going out the drain, this could pay for itself in four months.
Whether you are a homeowner or a residential or commercial builder, a drainwater heat exchanger is indeed something that you should specify for all of your buildings, whether new or old. It will start saving big money right away and forever after. And it doesn't matter whether you're in Sunny Florida or Cloudy Seattle, because it is your own used hot water that's doing the heating.
Here are a couple of commercially available units: