KrazyKuch's & Michika's 180Gal Tank Build

[mike31154]

Yes, there are calculators available to determine the appropriate size. Just Google tankless hot water systems and I'm sure you'll find some guidelines. My parents have a small unit manufactured by Rinnai. I would likely get a slightly larger one just to be on the safe side. Because these heaters heat the water through a coil/heat exchanger while it is flowing, if you have too many hot taps open at once, it won't be able to keep up. It also depends heavily on the temperature of the incoming water, which will be colder in the winter. For a family of 2 like yourselves, it shouldn't be a big issue, just takes a little coordination. Generally you wouldn't run bath water, a shower, the dishwasher at the same time. As for the water guzzling dogs... that's cold water and wouldn't affect the demand for hot water?

Here's a link with a quick rundown...

http://www.greenerbuilding.org/buying_advice.php?cid=56