Zone4 - you might not be happy but disclosure wouldn't apply here. There is no code requirement that applies (that I know of) and so there is no breach. It would seem that installing LP for that purpose alone seems a little extreme. One option - which has cheaper run cost and install than the LP tankless option - run a recirc loop from that bathroom to the tank. Have it on a switch. You turn on the switch and the line fills with hot water. The pump is $200, electric should be $200 and extra plumbing is $100. You won't waste water and as long as you shut it off, you won't waste electricity to heat the water. My $100 charges of course are guesses and the plumbing in the slab might be more. The $200 electric is what it would cost me in NC. You can of course put the kitchen sink on the same loop and install a switch at that location too. Recirc loops are done all the time but where you need to be careful is the energy loses because they are usually left on nearly all the time. By having them on-demand with switches, you counter most of those losses. To help with some of this, I would definitely insulate the slab plumbing lines. Another option would be to do solar for the hot water and use a 80 gallon tank. If the incentives are there, solar can be reasonable. I paid less than $2000 all in which is about the cost of your 2 50 gallon heat pumps.

Okay, I'm listening to what you are saying. Evidently 1.5 gpm is standard for an energy saving showerhead. A normal showerhead is flow restricted to 2.5 gpm. The next time I'm telling someone how to size a tankless, I'll include that information. And I'm all for using less water - but the 1.5 gpm number hasn't commonly been used in sizing. That said, when we are talking a shower with a rain showerhead, it's not going to be less than 2.5. I'm very comfortable with the 5 - 8 gpm number. What I don't know is the water temps in S. Louisiana in the winter. The average is 67... so is 60 a good winter time number? At 60F water inlet, the NRC98 will do 7.5 gpm - which is about right. Kudzu - Regarding "...almost 20 gpm of hot water..." this is an important thing I want to drive home with the OP and anyone else: You cannot look at that "best possible situation" gpm number on a tankless heater and think it will produce that. The only GPM number that's applicable is the amount of GPM it will produce given the temp rise needed to bring the groundwater in your area up to 105 F in the winter. Note: I made a mistake on the temp rise and GPM on my original example. I quoted the numbers for a 60 degree temp rise when it should have been 50 degree temp rise. At that rate a single heater would provide the needed GPM. I have edited the entry to correct it.

It is much easier to buy a new valve, separate it and install the center part which is damaged. There are 4 screws. Don't slam Spa Parts Plus. They are a wholesaler and are dropping the shipment to their customer. That is a lousy way of doing business. In the future, order from a local guy who can get the same part locally or through a distributor such as SPP. That new valve will not run much. Drain the spa, replace it when there is no water gushing all over the place. No glue required.

Besides cost, are there any other big issues? Recovery speed, space, speed of getting hot water to the tap? I can't help you with all of the costs but I can give you some general ideas: 1. Electric hybrid heat pump: Cost of unit is about $1100-1500 generally lowest cost of operation. time to get hot water to tap: Same as standard tank. Recovery rate: Same as electric tank. Design issues: Pulls heat from surrounding air - needs basement/garage/ etc. to circulate air. Makes some noise (like a refrigerator). 2. Tankless Gas: Cost of unit is about $1100-1500. Only slightly more to operate than #1 above. Time to get hot water to tap: about 10 seconds more than standard tank. Recovery Rate: will deliver continuous hot water up to max amount. Design issues: Must have large gas supply to the unit and gas supply to the house must be adequate. Makes some noise. Unit is compact and mounts on the wall. Vents with PVC pipe. 3. Standard Gas tank: Inexpensive to buy ($400-800). Moderate cost of operation. Time to get hot water to tap: Same as standard tank. Recovery rate: Faster than electric tank. Design issues: medium size tank. Standard gas supply. High temp venting can be expensive if new installation. Tend to contribute to air infiltration if not direct vented. Direct vent adds to unit costs but can reduce venting costs if it allows PVC. Requires clearances from combustible materials and air supply. 4. Standard Electric Tank: Inexpensive to buy ($400-800). Very high cost to operate. Time to get hot water to tap: Same as standard tank. Recovery rate: Slowest of all. Design issues: usually larger tank than gas because of slower recovery rate. Can be put in closets and such because there aren't air supply, venting or combustion clearances requirements. 5. Gas Tankless+Tank: Not common but out there. Most expensive to purchase ($1800-2500). Slightly more to operate than #2 above but less than #3. Time to get hot water to tap: Same as standard tank. Recovery Rate: Will allow large amounts of water to be used at the same time up to the tank size. Then will deliver continuous hot water at a max rate lower than #2 above. Tank recovers very quickly. Design issues: Medium size tank + tankless unit makes it bulky. Standard gas supply. Generally requires expensive stainless steel venting (non-condensing). Often can be direct vented. Makes some noise.