[Greenbuilding] is it ever sensible to use PV to heat water?

[Reuben Deumling]

Thanks for that article, Kat.
I don't know. Seems to me he's having a little too much fun chasing the
provocative title. It is of course true as I've said many times here that
in the Pacific NW, or the part of it where Charlie Stephens and some of
the rest of us live, is not going to do much for heating water with
sunlight in the winter, but that is true for both PV and solar thermal. The
fact that grid-connected PV can 'bank' the sunlight and solar thermal can't
is only sort of relevant in my book, and its virtues are mostly deceptive.
We have a winter peak here in the PNW, thanks to the legacy of cheap hydro
electricity and the widespread adoption of resistance heating (space and
DHW) it spawned. Adding PV to that only exacerbates the peakiness of the
grid, and sucking electricity from our grid in the winter to heat domestic
water is not something I'd ever support, Martin Holladay's calculations
notwithstanding.

I appreciate the (micro-)economics for the systems he describes, but wonder
if instead of those oversized commercial systems we looked at something
more suited to actual demand by the average 1- or 2-person household, what
the numbers might look like?

Marrying a solar thermal array to a wood stove water jacket seems a far
better and more elegant design that takes into account the larger questions
Holladay's article elides. It actually works well seasonally, and the
system costs would not have to be up there at $10,000 either, especially if
you keep it simple (thermosyphon, modestly sized).

But I'd be curious to hear other reactions to that article.
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