i just had an on-demand/tankless H2OT water heater installed.
The most common brand may be Aqua Star, which i had in my
previous house, and the one I have now is Infinion. I believe
Bosch may have bought out Aqua Star (they are both French i think)

akwakai makes the infinion their number is 1-800-247-3619
they are from near Seattle. They are available with two
options for lighting: pilot light and piezo ignition unit.'
the pilot light uses quitye a bit of gas, but keeps the
unit warm and hopefully prevents freezing (mine is mounted outside)

I am glad you are going to replace the shake shingles...
they are a great fire hazard. but make great kinkling for your
fire place!

i have friends who have had good luck with a paloma brand too.
http://www.gaswaterheaters.com/pdf/
quite a few types are compared on this site.

since a tankless water heater can produce endless supplies
of hot water, limited only by available water and fuel,
you could get a hot tub full of water with no problem..
I'll be arriving shortly with my rubber duckie and towel.
See you soon!! I actually had a nice bathing experience
last time i was in your neck of the woods...
just to the south of "Pokey" is the Lava Hot Springs
and that was my 1/2 way stop on my 800 mile day between
Bozeman and Elko!!
when you cut that red carpet into strips,
just lay it out in the driveway to welcome
all your well-wishers!! see you
oh veggie pizza with pesto is my choice!