Help size GPM for small house

[Jeremytl]

I'm replacing a 40 gallon tank heater that is in my crawlspace with an electric tankless heater. I don't have propane or natural gas available where I live.

My first question is, can a home pass inspection with a water heater in the crawlspace sitting on dirt?

My second question is how many gpm tankless heater should I get for the house described here:

1,300 sq ft, 1 and 1/2 bath (one shower and lavatory, another just a lavatory).

The full bath is at the end of the house where the existing tank heater is.

At the other end of the house is the kitchen, washer and half bath. We don't have a dishwasher so the kitchen sink gets used quite a bit. We rarely use hot water in the washer because it takes so long for the water at this end of the house to get hot. Hot water in the half bath is hardly ever used.

I would like to replace the tank heater with a whole house heater in the same spot under the house.

I have an account at Home Depot so I'd like to use one of their brands. I'm currently looking at the Stiebel Eltron Tempra 20 2.91 gpm model. I have a very limited budget and this is in my price range. Do you think this heater will be sufficient?

I'm thankful for any input.

 

[Jeremytl]

Nevermind, I just learned that the main switch in my panel is only 100 amps. I would need a pretty stout electrical upgrade for the entire house. I'm back to replacing the tank.

 

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[WoodenTent]

Maybe it's too late, but some comments. I'm in michigan, have a Tempra 29 for a house similar to yours. Since your in N.C. your ground water temps should be much higher than here. It's all about temperature rise. If you know your winter water inlet temps, that's a big help. You can use Steibels graphs to see where it would fall. Mine should pull 120amps full tilt, but due to de-rating it stops at 104amps. And to do that I need to open the old tub valve full open, otherwise I don't have enough flow demand to max it out, so most the time it's way under it's rated need. Is your tanked unit under the house? If it's in the conditioned space you could put a conditioning tank in there before the water heater, so the tankless only needs to go from ~70F to ~110F which cuts down on the size needed.