"Doctor Drivel" wrote in message
reenews.net...

"daestrom" wrote in message
...

"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/

What was the payback period?

I have a family of five. Even with a low-flow shower head, that works out
to about 34000 gallons of water a year. Of course it's mixed hot and cold
to create just a nice 'warm' shower of about 100F. The average year-round
water supply temp for me is 55F. So that works out to about 127 Therms of
NG a year. When I bought the thing, NG was $0.80/therm. The payback with
that 5% interest on $270 worked out to just about three years. With NG
prices running $1.30/therm, it's under 2 years. But mine has already paid
for itself.

daestrom