I'm fairly new to geothermal. I've been reading a ton of information and have just received my first proposal. Background: My 1950s brick rancher (1900 sq ft incl 900 sq ft finished basement) has two HVAC systems: 1) baseboard radiators on a natural gas boiler, and 2) natural gas furnace with ducts. Most of the upper floor has only ducts, and a two-story addition on the back of the house has only baseboards; most of the basement has both ducts and baseboards. The gas boiler is more than 40 years old (!!), so my primary goal is to replace it with a GSHP before it dies on me and before that 30% federal credit starts to phase out. With today's gas prices I'm not embarking on this project expecting huge savings. Cost is a factor as it is for anyone, but I'm also motivated to reduce my carbon footprint to the extent I can afford. So, here's the broad strokes of the plan: 1) Boiler replacement: I've settled on the WaterFurnace 504W11 because it can get hot enough to work with the existing baseboard radiators. 2) Furnace replacement: The furnace still has years of life, so I will might leave it as is for a few years. Eventually the HP will heat the whole house (and is being sized in advance to do so), but if I decide to delay adding an air handler I may wait til I can afford to run radiators to the duct-only part of the house. (I kind of hate forced air heat from a comfort standpoint.) At least one installer has recommended keeping my gas furnace as a source of aux heat. Would anyone here recommend differently? 3) Cooling: I'm currently using a decidedly un-environmentally-friendly 7 window A/C units for cooling. The WF will take over cooling whenever the NAH is added. 4) Domestic hot water: Current DHW is a fairly new (2009) 60-gallon gas water heater. This is where I'm feeling the most confused about my options. Here are the options the first proposal came with: Desuperheater - $1475 w/o storage tank; $2000 w/ 50-gal tank As I understand, the DSH (with or without storage tank) is just for preheating and cannot replace the gas HWH. I've also read on these forums that DSH perform poorly with gas HWH - would there be any point to this if I keep the gas HWH? Electric water heater - $2892 for a 75-gallon Marathon water heater Is there any advantage to replacing my gas heater with an electric one given it's still pretty new? How would Marathon with DSH performance compare to gas HWH alone? On-demand geo water heater - $8848 for NSW025 water-to-water with geo storage tank Aside from operating costs and carbon footprint, are there performance differences between electric and geothermal water heater? Solar - $9626 for 20-tube flush roof mount with 80-gallon tank I'm honestly not sure I get enough sun exposure for this to be viable due to many tall trees (cutting them down would be illegal). I once plugged my address into a website to see if rooftop solar was a viable electric source for me and was told it wasn't, but maybe hot water doesn't need nearly as much sun as solar panels? How do operating costs compare to geo water heater? Change nothing - $0 Any special considerations or pitfalls to be aware of if I just leave the gas HWH running like it is alongside my geo system? Edit: After doing more research it's looking like it's going to come down to I don't enough space for the geo heater to make sense. Space is already pretty tight with the furnace, boiler, and gas heater. It also looks like the solar solution would require yet another extra tank to store the solar heated water, although maybe not as huge as the existing 60 gal water heater? At this rate my basement will be full of tanks! Hot and cold buffer tanks for the heat pump, a solar storage tank, and the existing water heater. So now I'm leaning towards just sticking with the gas heater until it's getting ready to die and re-evaluate then. Maybe someday when I build my upstairs laundry room I'll be able to take the washer and dryer out of the utility room to make space for this tank farm and add the solar at that time.