On Fri, 15 Jun 2018 23:15:52 -0400, Clare Snyder
wrote:

On Fri, 15 Jun 2018 08:07:32 -0700, Oren wrote:

On Thu, 14 Jun 2018 17:17:35 -0700 (PDT), Uncle Monster
wrote:

Big factor for me is with a tank you have hot water during power outages
that lasts at least a day, if you use it reasonably. You could even
take a couple of very quick showers if necessary. And with natural gas
and a basic tank type with a pilot light, you have unlimited hot water.

Years ago, I installed a Bosch tankless natural gas water heater that had its own generator for producing the electrical power for the controls and igniter. It had a little paddle wheel that spun a small generator inside a closed housing that was part of the cold water side of the heater. As soon as the water started flowing, the burner came on and there was continuous hot water. If I had the money, I'd look for a tankless water heater like that. ^_^

[8~{} Uncle Gassy Monster

I've seen these units installed, three (3) zones in one home, 2 units
mounted on outside walls, (1) in the garage with just the gas supply.
I believe it is called (?) an 'inline turbine'. When water is called
for, the turbine spins and makes ignition. No need for a AC power
supply.

That;s ok when they work - - - -

Turbine igniters work when demand is called. Tankless is easy to DIY
repair.

I've said here many times I like tankless, also said before I would
never retrofit into a current home. New construction is the better
choice. PEX, a manifold with brass 3/4" turn ball valves. Oh. and add
in the utility company change to a larger gas meter.

OP never mentioned sizing the gas meter to the unit demand.