Dear Solar Guy,

         I'm confused.  I have contacted several vendors about putting in
a solar water heater and I get different advice about the system to put in:
single or double tank, 60 or 80 gal. tank, with or without a heat
exchanger, how should it be mounted, how economical it is, etc.  Come on,
why can't a person get a straight answer !   

- Confused in Comfort !

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Dear Confused,

        Yes, I can empathize with you, as there are many "wrinkles"
relative to solar hat water (SHW) systems.  There is really no "one"
answer to your question.  Let me try to give a little general advice.

        The economics will be better if you are replacing electric water
heating than replacing a gas water heater.  Typically one needs about 15
or so square feet of collector per person and about 50% more in gallons of
storage as square feet of collector.  That is, with 4 persons in a
household one needs about 50 to 60 square feet of collector and about 80
gallons of storage.  If you have electric back-up, then use a single tank
and have only the top electric element activated.  There are several types
of system configurations that relate to freeze prevention, and I would not
recommend the circulation freeze prevention design.  Rather, select either
a drain-back design with a heat exchanger or an anti-freeze design with a
heat exchanger.  The other decision is how and where to mount the
collector.  One usually hears: "Mount at a tilt equal to latitude plus 10
degrees and directed due south".  While these are preferred, the
performance is little affected if within 10 or 15 degrees of this tilt and
within 3o degrees of south.  Aesthetics and wind loading in conjunction
with your roof orientation may warrant deviating from these recommended
values.  A friend of mine has said: "I've never seen a roof that a solar
collector could not be mounted on and still perform well and have good
aesthetics".  The other thing is who to buy from ?  As in any purchase,
buy from a reputable firm that has installations in your area which you can
inquire about.  It would be highly advisable that the firm is a member of
TRIEA (Texas Renewable Industries Association).

        Oh yes, I see I've stressed active systems (with a pump) as
compared to passive designs.  If I get a request about passive water
heaters (or even if I don't) I'll talk about them next time.   Hope this
helps !   

 The Solar Guy.