Kelly- Packless provides a nice design for water cooled heat exchangers. A lot of HVAC OEM's today use Packless heat exchangers or similar in their watersource heating and cooling designs. Pool Heat pump OEM's also use a design similar to Packless with special coatings/materials to survive pool water chemistry. The use of these heat exchangers to pre-heat potable water works well in low and medium temp refrigeration systems such as those used in walk-in coolers and display cases found in grocery stores. These refrigeration systems already have sophisticated refrigerant metering devices that properly control the metering of liquid refrigerant into the evaporator and provide adequate superheat returning to the compressor to prevent liquid slugging which will cause compressor failure. In high temp applications such as residential HVAC, the use of watersource heat exchangers prior to the condensing coil will work but will require a lot of sophisticated controls to be added to provide the right amount of subcooling and superheat to the system for reliable refrigerant metering extending the life of the system. After considering the cost of adding the needed refrigerant metering control devices and head pressure control plus being only able to heat the pool water only when the AC system is in use appeals to only a small number of clients. Not a large market at all for a product such as this. There is actually a DOE funded project going on right now called "net zero engergy" homes. The concept is the home should be able to produce enough power to meet the homes energy requirements hence net zero energy. The HVAC systems in these prototype homes use water cooled heat exchangers for hot water heating. Even with the small load of hot water heating in these homes, the HVAC technology limits are being pushed. Heating a pool would require much larger amounts of heat to be practical in every day use when combining HVAC systems and pool heating. Of course, those who like to tinker and have available assets and hardware to play with will benefit from the additional heat provided by these AC system heat exchangers but the risk of a compressor failure go up considerably when these head pressure controls and refrigerant metering devices fail down the road. There are high efficient HVAC systems available today that use water to cool the condenser. These systems are called closed-water-loop geothermal HVAC systems and are very efficient because the cooler water is used to reduce the condensing temps which considerably reduced compressor head pressure and operating power. These watersource closed loop HVAC systems have been around for a long time and could possibly be adapted to heating a pool easier than the proposed method of using an existing air to air HVAC system and retrofitting a water cooled heat exchanger to it. This would also save a lot of coin on your heating and cooling costs as the heating and cooling efficiency will be a lot better than your existing air to air system. Not sure what pool water chemistry would do to these water cooled heat exchangers but listening to those in the watersource HVAC industry, water chemistry is the biggest contributor to heat exchanger failures on these watersource HVAC systems. Hope this helps!

Tigerdunes, you are correct in most aspects, but the selling back excess is the sticky point right now. The selling of electricity to the utility from renewable power sources by individual customers is governed by local PUCs. In some places, you get nothing or virtually nothing for excess. Furthermore, in places you lose any excess at the end of the month, it does not roll over. Others, maybe you can't roll over at the end of the year. Some net metering agreements require the utility to pay the customer if there is a chronic overproduction. In some of those cases, you only get paid when you disconnect from the utility. (When you move or die.) That is like a no interest bank account/retirement fund. The agreement is so bad in some areas that with the price of panels going so low, homeowners are better off buying batteries. That is something not dreamed of as economic not long ago. Installing big water heaters or freezing ice and using it to cool the home at time of high demand are alternatives. Definitely consider that the lifetime equipment costs of running a furnace vs, a heat pump when doing calculations to determine cost and environmental impact. I don't know if the ability to recover retail cost of excess power can tip the balance to make a heat pump favorable or not, but it might.

Propane has 91K btu's per gallon input, Electric has 3400 Btu's per kilowatt. Propane gives you 72,800 btu's output at 80% efficiency. Electric aprox. 3400 Btu's output per kilowatt, (100%) with only a small amount lost. 72,800 btu's divided by 3400 btu's = 21.4 kilowatts to equal 1 gallon of propane. The average cost of 1 kilowatt in Austin - $0.1142 cents, times 21.4 Kilowatts equals $2.42 for electricty and little more expensive then propane at $2+ per gallon. But this will change drastically if Biden does ban fracking as he stated. But then what happens to the price of electricity? It's a guess, and having the ability to switch between the two may be a valuable option in the near future. But the cheapest option with a stable price for ever would be to capture the heat in the sun with active solar collectors to heat water (not to be confused with solar panels to produce electricity), and store it in insulated underground tanks to use for the winter. After the initial investment it would cost you a few dollars a month in electricity to run circulation pumps, and you could even get the electricity from solar panels for that. They do it in Alaska for building bigger than yours, easy and simple, only problem is getting insulated storage tanks in the 5K to 20K gallon range. I'd do it in a heart beat if I had some really big tanks, I have the land, backhoe and the solar collectors, 9 of them 5' x 9', salvaged from a $35,000 government subsidized program project in the late 70's. (The government loves wasting other peoples money.) Johnson controls started a line of HVAC equipment called champion about 6 years ago. Parts?

I would say it greatly depends on where you're building in Texas. Natural gas is still the predominant pick here. If you're more rural, then yeah propane or heat pump with electric strip back up / emergency and in some cases just electric strip only. Heat pumps have come a long way over the last several years. But in colder weather the cheaper models performance drop off a cliff usually somewhere in the 20 degree range or so. As they often spend more and more time in defrost under those conditions. What recently happened with the freeze: most didn't have heat anyway. Weather gas or electric you still need power. I know you say you have a generator but most do not have those. The freeze was hopefully a one off event not to be repeated for 10 or 20 years. It doesn't get that cold here that often (Katy, Texas Area). 2011 was last time, before that it was like 1989 or something like that. That said this last time wasn't the coldest ever recorded temp. That was 5 degrees set on Jan 18, 1930. Heat pumps work by pulling heat from outdoor air (cold air) then taking that heat from that cold air and pumping it indoors. As temps fall (outside) there is less heat. Also below freezing any moisture in the air will freeze on outdoor coil making it harder still to extract that heat. Then if the heat pump enters defrost it is now running in ac mode making the indoor coil "cold" if back up heat strips are inadequate / improper set up for "really cold" weather that we rarely get here. Would you want to pay "extra" for something you might never use? I've had discussions with people that decide to stick with strip heat only because they don't want the extra expense to install a heat pump. Even though the heat pump can save you upwards of 75% off what it typically costs you to run strip heat. Just a couple of chilly winters here can make up that cost versus strip heat. Propane is probably similar. But many a winters... it's like 2 weeks and gone or sporadically over a month or two. So heat pumps are still quite the debate. I have an Inverter heat pump at my house. Those aren't for everyone... it's a choice. I bought it more for what it does on the AC side of things rather than heating. It's often more of a challenge to keep things cool here. It also does a better job of dehumidifying.... which for my neck of the woods in Texas is the other elephant in the room.