Phased Construction-Two Electric Tankless Hot Water Heaters?
Climate Zone 3. Distribution water at tap temperature estimated to be 50-55 (finish water temp as it leaves the water plant). I’m phasing construction: Phase one: 1st floor shop/garage. One shower/one lavatory sink/one shop sink. Phase 2 is the upstairs living quarters that are estimated to be finished out within next 3-5 years. The electric service to the shop/home is 2/200 amp services. We are planning one panel for the 1st floor shop and one for the 2nd floor living quarters. ( I say living quarters..it turned into a 2000 square foot 3bd / 2bath space-basically a home!).
I’m considering wiring the 1st floor utility room with enough electrical capacity to support two tankless water heaters. The utility room is directly adjacent to the 1st floor bath/sink/sink and was sized space wise for a conventional tank heater AND a water softener. Plenty of room if occupancy loads changed for future owners. (We are only two adults and occasionally host a few house guests)
1st unit would be sized to handle the
primarily 1st floor
1 bath sink
1 shop sink
maybe the upstairs dishwasher (2nd floor future-close proximity to 1st floor bath)
Even when house is fully occupied it will be rare/almost impossible that all fixtures would be in use simultaneously. It would have to be done “ON PURPOSE”
2nd unit would be sized to handle
all 2nd floor
2 bath sinks
1 kitchen sink (close proximity to 1st floor bath)
1 clothes washer (we run only run whites/bedding in HOT).
The 1st floor will only be utilized as hobby shop for the next 3-5 years. The 2nd floor space (Phase 2) will be completed on a cash basis however all the hot and cold plumbing lines will be in place (in the 1st floor ceiling/2nd floor floor space) prior to insulation and drywall of Phase 1-1st floor.
Any thoughts on this approach? Gas is not an option I want to pursue. Other alternative would be to go traditional tank style, size for max capacity (or not-maybe just buy a mini), turn it to low when not in use. If the two tankless are viable, would it be wiser to install the 2nd unit upstairs in the Laundry/utility room? There would be space for it in a broom closet sized space. I’m looking at Marey or Rheem 27kW for the 1st unit. I apologize for the length of post…but the devil is in the details!