Dual Heaters?

I'm building a new house and am looking for some info on putting in dual water heaters. I had originally planned to install a single 80gal electric water heater, but my plumber suggests 2 - 40 or 50 gallon heaters plumbed in series instead. I think either will be more than adequate for the 3 bath house but I'm somewhat concerned about the cost to operate the duals. Does it cost twice as much to operate a set of duals as it does to operate a single of the same type? What I mean is if it costs $350 per year to operate a single 50 gallon heater, would it then cost $700 a year to operate a pair of them in series? Or does it not work that way since one doesn't see as much use as the other? I have room to set them side by side, as well, so one would directly feed the other with not much pipe between them.

And which setup is better in your opinion, a single 80 or 2 40s/50s? Obviously dual 50s gives you 20gal more hot water, but are there any other advantages over a single tank?

We do have a rather large whirlpool tub in one of the bathrooms that has a 55gal to operate and 110gal to overflow capacity. And the wife swears she'll use it every single night, we'll see. I still think either setup would handle it.

good setup

there isn't anything wrong with two 60s in series as opposed to a single larger one. The first one acts as a preheater, bringing cold water up to a warm termperature. The second one does the next level of heating. Several threads here have dealt with this.

David

Most of the cost is to bring the water up to temp. Once it’s hot it dose not cost much to keep it hot with the newer heaters (as long as there are not in an unheated space).

I would go with 2 50’s and have him plumb them in series with bypasses on both. This way you can cut one off and still have one on. This will be nice if one has a problem, she doesn’t use the whirlpool, and so on. You could cut the water and the power to the one, drain the tank, and still have hot water to the house.

I have seen a few post on weather you should go in parallel or series but it all comes down to the in series the first tank dose more work so the elements will burn out before the other one. But what are a few elements.

heaters

All electric heaters heat water at the same rate, so if you have two of them they will heat the water twice as fast, giving a faster recovery rate.

I prefer to pipe dual/multiple heaters in parallel.


http://www.hotwater.com/bulletin/bulletin64.pdf

I have done them both ways. But when I set them up I set them so you can bypass either tank so you can work on one and still have the other one working.

If there in parallel you can get more volume depending on how the plumbing was run.