the geothermal should more than take care of the rest of your home's needs if set up correctly. This is not necessarily true. This depends on what area of the country you live in and how your system is sized (to save upfront cost and increase the ROI geothermal systems are often slightly undersized from the peak loads). In our area desuperheaters can only pre-heat the hot water before heading to the hot water heater. The highest they can heat the water is 90degF and that is only in the middle of summer. Our hot water heater then has to take it to 120degF. In the heating months the desuperheater barely heats the water if at all. The temperature of our well water is warmer than the antifreeze/water mixture leaving the heat pump coil. The whole concept of ground source heat pumps wouldn't work otherwise. Beaglesdoitbetter, unless you live in an area that is never in the heating mode you need an additional hot water heater. But I agree with live_wire_oak that you should try to consolidate the hot water systems if you can. There is no need to have so many different units and different fuel types unless you have a large sprawling house where the water would get going from one end to the other. Your builder is probably talking about needing to add a holding tank if you use a tankless water heater. A desuperheater is just a heat exchanger between the water/antifreeze mixture (it may be water depending on where you live) that is leaving your heating coil and the water line going to the hot water heater. Most knowledgeable installers will also add a holding tank between your heat pump and your hot water heater so that in times of high hot water use there will be plenty of preheated-fully heater water waiting. Typically this tank it is just the shell of another hot water heater with the guts removed (you want the tank to be insulated). Some installers try to get away with not adding this holding tank and the whole system still works because a traditional hot water heater is used. If you go tankless they are required to add this holding tank. Either way I would make them add it in. It shouldn't cost much more. A tankless will need a bigger fuel line though which may be another reason your builder was trying to steer you away from them.

I WISH I could buy electricity for 7 cents per kilowatt hour Still at just a dime, that's 80 cents per each 12 hour period of time, or $1.60 per day times 365 days per year which equals a pretty substantial $584 per year - Far more than a new water heater costs Since my solar panel does this for free, not to mention the fact that it also heats my 65 degree well water up to the previously mentioned 130 degrees, I would have to guess that it's saving me more than $1K per year - If so, I'm looking at less than a 3 year payoff for the money I invested in the system ;-) Don

The above calculations hold true if the water heaters are connected in tandem however, if two 50gal water heaters are connected in series you begin with 100gal of water and as the dilution begins in the first water heater, the slightly cooler water enters the second tank where is is raised to the desired working temp, thus you can create a nearly continuous flow. In addition, when connected in series the first tanks temp control can be set about 10deg higher than the second tank thus under lighter loads the water will pass through the second tank without triggering the burner. In this manner under lighter loads the second tank functions solely as a storage vessel thus saving energy. On the other hand, there is a much bigger problem that generally goes unnoticed by homeowners. While most homeowners think of a shower in terms of the entire shower enclosure which is primarily intended to be a single occupant facility code must be capable of defining both the supply and drainage requirements of all showers, whether it is the single occupant residential facility or a large gang shower such as might be found in a school or factory locker room, thus for the purposes of estimating supply and drainage the code defines a shower as the shower head, thus when two or more shower heads can be operated simultaneously, we must allow the full code minimum water supply for each shower head. By example, under the IRC even though shower heads are restricted to a maximum flow rate of 2.5gpm, code requires that we size the piping for 3gpm. If we then design a shower facility with one shower head and 6 body sprays code would require the supply piping to be sufficient to supply 7 showers at 3gpm per shower for a combined total of 7x3gpm =21gpm. When using copper pipe code limitÂs the velocity of flow to a maximum of 8ft/sec thus to get the code minimum 21gpm supply, it would require an 1-¼" water line and 100gal water heaters. In turn, we must also compute the drain load at 2dfuÂs for each shower head, thus the combined drainage load for this shower would be 14dfuÂs, which would require a 3" drain line. I would strongly suggest you have a long talk with your local inspector before commencing this project.

As I alluded to earlier the minimal storage is an advantage. There are two seemingly conflicting safety issues around water heater temperature  the risk of scalding from excessively hot water, and the risk of incubating bacteria colonies, particularly Legionella, in water that is not hot enough to kill them. Both risks are potentially life threatening and are balanced by setting the water heater's thermostat to at least 50 °C (120 °F). The European Guidelines for Control and Prevention of Travel Associated Legionnaires Disease recommend that hot water should be stored at 60°C (140 °F) and distributed such that a temperature of at least 50°C and preferably 55°C is achieved within one minute at outlets. If there is a dishwasher without a booster heater, it may require a water temperature within a range of 57 °C (130 °F) to 60 °C (140 °F) for optimum cleaning, in which case tempering valves set to no more than 55°C can be applied to faucets to avoid scalding. (Note: Tank temperatures above 60°C may produce calcium deposits, which could later harbor bacteria, in the water tank. Temperatures above 60°C may also cause gradual erosion of glassware in a dishwasher.) ItÂs interesting, as many communities and watersheds heavily chlorinate the water delivered here in the US and the concerns is virtually of no concern. Personally knowing someone who set his indirect hot water heater lower than usual and taking long showers while sick and congested, caught the disease, and it was nasty with harmful effects still huanting him