Water Heaters - One or Two Hot Water Heaters?

I am finishing up a remodel of a bathrom and I have a body spa that if used will need about 100 gallons of hot water at a time. I would like to have about 120 gallons of hot water capacity so when it is used we still have a little hot water left. It will have to be an electric water heater because gas is not available. I hate the thought of keeping 120 gallons of water hot all the time when I will only need it a couple times a week. My initial thoughts are to use two 60 gallon tanks shutting one off until needed.

Is this possible? If so should I have them plumbed in parallel or series?

Tankless heaters are not really an option because I would need two large units and I don't have the breaker box amp capacity to support them. I already have electric heat and a 4.5 ton heat pump plus two ovens so the box is pretty well maxed out as it is. The power company will not let me install a 300/400 amp box for residential use.

Thank You
Frank

You want to put them in series for sure. You could get by then with 2 --50 Gal. there, When done turn off the first tank. Have did this a lot and it works good You see as you use the hot water . The first tank will turn on and warm the water some as it goes to the #2 tank by then two elements can be on one in each tank . Have also above the union on the tanks put a shut off valve in the hot and the cold water lines. then a T from the cold to the hot with a valve in between them. This way you can shut off any of the hot water tanks you want to work on clean or what and still have the other tank working just fine. Have homes in Mo with 400 amp panels and better in them with UE

ED ;)