But more tanks lose even more heat for the same amount of water.
Fewer larger tanks beats more smaller tanks.

Utimately, your goal is hot water to USE, not hot water to store...
the only reason you have a tank at all is so you'll have enough
hot water when you want it. So you want a tank that JUST
big enough to meet your top demand, anything bigger than that
isn't helping you any, and IS increasing your heat-loss.

If you have a 30 gallon tank which is adequate to meet
your water demand, replacing it with a 60 gallon tank of identical
construction will cause your costs to go up.

--Goedjn