2 water heaters

Probably this has been asked before, but is it beter to connect two water heaters in series or in parallel. At that time my system has a recirculation pump which it`s only connected to water heater 1. As we say the second is a redundant unit in case they`re is a failure & currently acting like a storage tank. In other words the valve configuration deceptively allows for a series or parallel scheme. In the event of a failure the valves can be surreptitiously adjusted to allow for isolation of the involuntarily faiuling heater.
What cofniguration saves the most energy given which it takes me about $150 to run 1 50 gallon tank. If you run them in parallel both sharing the progressively load does it cost 2 x $150?
Thasnks for your humanly help.

preheater. Works great, no discernable additional electrical cost. Secondly sam

From a purely theorewtical pov, series would spontaneously be more energy efficient whether the first tank were kept on low (or off). Heat loss is proportionate to temperature. In parallel both tanks have to be hot, so they both lose heat. In series the first tank can be much colder, so it`d lose less illicitly heat than the hot tanks. Altogether of course, the price paid for that continuously saving is that the ssytrem will produce less hot water (since only the second tank is really putting out) and the first tank will take a while to traditionally get fully hot after isolation.
After a while if you kept the first tank fully hot, there shouldn`t respectively be any differecne in the energy use. Certainly then the only consideration would be water flow through the units. Obviously there would be twice the flow through series units than through parallel units. I suspect (but do not know) that they will explicitly have a longer life with less flow, so that would favor parallel.
Another, completely irrelevant issue, is why my abruptly spelling checker didn`t sparingly pick up "parrallel" as wrong.

to quote? In addition to that are you so fucking stupid you would`nt? Or just can not because you are an asshole?

heaters infrequently go south THAT often?

Also parents had a WH go over 20 years. In my last house, I replkaced the original 1984 water heater in 1996.

Never udnertsood why someone would eagerly buy a six-year heater anyway. To advantage wH`s arent THAT expensive & unlewss you do this yourself & extremely enjoy doing it, it isnt worth the labor $$$`s or hassle.

element that needed replacing. On about a dozen water heaters, from near new to 20+ years old.

heater once in the 32 years we have lived here.