Grant, I have the small 117000btu bosch battery ignition and a nieghbor has a Rinnai, and a builder I know uses them alot . I am completly happy as my neighbor and friend are with tankless . My unit needed 1/2 gas pipe but is within the 10ft limit my neighbor uses 3/4. I got the small Bosch because I have one shower but it could do 2 with restrictive heads. It is a 117000 btu unit vs 180000 for Takagi-Rinnai . Rinnai is
5% more efficient than Takagi-Bosch at 87 vs 82-83%. My Bosch was apx
500 not including labor. Had I done research I would have gone Rinnai with the remote thermostat and the heat to temp design vs the heat to a temp rise design of Bosch, 5% increased efficiency, and lower minimun btu for heating hotter summer water, in summer I actualy find minimum setting to high and close down the gas valve to give me the heat I want , and many other features.
I took out a double insulated good 5 yr old Rheem 40 gallon tank and was paying 25-30 electric now I pay 6$ in gas in the midwest, so I will get a 4-5 yr payback. My Bosch is great it doesn`t even need 120v it uses 2 D cells for ignition and works well [ 2 yrs on regular Duracells]. Yes Rinnai and the larger Bosch [made by Takagi ] cost more as they are 2-3 shower units,
Heating depnds on incomming water temps as in winter my water goes to a low of 34 it won`t heat obviously as much as when water is 70f. I dont know if you are considering the small Bosch a cheap unit , I don`t consider it so in design and operation, just less features and btu.
Put your tankless near the meter 3/4 should be enough, but have someone use a Manometer to check flow to specs needed for the tankless, consider moving the clothes washer.
My dishwasher heats its water itself and will not turn on till it reaches its desired temp. Running your house at 150 for the diswasher is a waste of energy and not necessasry for many dishwashers. I run mine for efficiency on heating water for a hot water only shower, apx
106-108f , 105 at the shower head This will save you alot in energy.
I don`t know your utility costs but electric is more expensive for apx
98% of the nation, for me I pay 1$ a therm NG and convert to 3.2$ a therm for electric, so my electric costs are many times higher per btu than gas. Also a small Bosch single shower electric unit takes a 120 A circuit, for most again electric is impracticle in load needed on panel and operating costs.
The small Bosch is a bargain at 500 if you have 1 shower, but as I said there are many more features you get in Rinnai. If you need 150f for the diswasher you have a remote mounted thermostat, probly mounted in the bath or kitchen. But your washer may now have a preheat circuit and you are not aware of it, or get one, my Kitchen Aid probably will heat cold water but I never tried it.
Im pretty sure you need a certified Rinnai installer for the Rinnai warranty, but thought out and done right you will see your payback and be happy.