If you are thinking of removing your conventional storage/heating tank and replacing it with the tankless think about this.
a) Keep the storage tank in place to allow the cold water to come into and over time will reach a nominal temperature. Add the tankless to the outlet side of the existing conventional storage/heating unit.
b) If your bathrooms,(hot tub), kitchen and laundry are far apart you might want to consider point of use heaters. You will get better response and will only be heating what you use.
The hot tub should be out of the equasion as it is an isolated closed loop system. Unless you fill it from a hot water spigot somewhere.
You have a large house for just the two of you. This might be the way to cut down on energy use.
Point of use heaters would be similiar but smaller than the tankless you mentioned. But you would need one at each point of use. Expensive? yes! and no! But may be an attractive selling point.
For point of use water heaters, do a google search or try:
http//:
I am not affiliated with the above so I cannot give you a bonafid affidavidt.
Not knowing your motivation for the choice of tankless over conventional water heating limits the response from other very capable members on this site.
It might also be in your best interest to post this question on the HVAC Forum or Thermodynamics Forum.
Good Luck
pennpoint
