Thread: Water Heater sizing

This may have been a subject before but I could not find anything.
Three bedroom house with 2 full baths. Had a gas direct vent water heater size unknown because it was replaced with a 40 Gal electric water heater when the upstairs was finished off. They added another bedroom and bathroom upstairs. So the home is now 4 bedroom and 3 full baths. One bath has garden tub. A 40 gal. WH is undersized is it not? By what means do they calculate the size of a water heater for a home. Is there anything written?

Thanks

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Lots of recommendations but have not seen actual code.

50 gal electric would be considered on the low end for that house.
75 gal electric would be considered good.

A hot water circulation loop would help a lot if they keep the 40 gal.

State water heater manufacturer has a table on their web site.
State Industries | Residential Sizing Guide

Thanks guy's
You would think they would come up with some set standards in the IRC

I'm a little late to this party, but, for what it's worth, Georgia adds this table to the end of chapter 5 of the IPC (we don't use the IRC for plumbing around these parts) .....