"Derek Broughton" wrote in message
...
Ron Purvis wrote:

I think you are off on your figures. According to
http://www.fsec.ucf.edu/solar/apps/sdhw/dhwsave.htm the typical home uses
20 gallons of hot water per day for the first two persons and 15 gallons
of hot water for each additional person. That would be 25,550 gallons of
hot water per year for a family of four.

OK, I'll accept those numbers. Anyone got a better figure on the average
cost of heating water? My numbers for heat required are, if anything, on
the low side, but at $25/million BTU, and only 25,000 gallons per year,
you're talking $250/year (somebody else said $20/month, so same ballpark).
Still plenty to make a commercial solar water heater pay off.


I cut my DHW heating by somewhere between 1/3 and 1/2 by installing a
waste-water heat-exchanger. Running hot water for a shower and letting all
the energy go down the drain (literally), just doesn't make sense. Of
course, this system only recovers heat from *running* water, so baths and
dish washing doesn't affect it.

I have one of the largest units and it is a two-pass type so is not the most
efficient model they have. Mine cost only about $270, did the installation
myself.

http://www.gfxtechnology.com/

daestrom