Installed radiant floor (concrete) in a walled off 21'x60' section of the
shop. Works wonderful. (Northwest, Oregon). Have used it for two winters.

My propane supplier said that I should have gone with a "tankless" heater
instead of the ordinary (heavy duty) tank type water heater. Claims the
savings would be tremendous by not keeping 50 gallons hot, on tap 24/7.

I'm trying to do the math and need some advice. Logic tells me that I would
have to sit in the shop for 24 hours and add up all the RUN times, while the
water is circulating through the floor, in order to calculate the OFF time
within 24 hours. Then I would have to figure out the cost of keeping water
hot during all of the OFF times. This would be a factor of heater
insulation etc. and might be available from manufacturers etc.
BTW, in addition to floor heat I will be adding one bathroom (maybe three
handwashings a day?) with shower (maybe two three showers a month, if I am
too dirty to be allowed into the house).

Any simpler advice from any of you out there? These on demand units are not
cheap. My supplier tells me that he runs a four bathroom house (4 family
members) with a single "on demand" unit.

Thanks, Ivan Vegvary