I live in the Pacific Northwest and have a 5 year-old hybrid, propane heating system that heats water to 165 deg and runs through a coil in an air handling unit to provide forced air heating. There are two air handlers (2 ton and 3 ton) with 3 zones on each one for a two story, 4300 sq ft. house with 10 ft and 9 ft ceilings. The heat / water source is a 100 gallon tank (A.B. White) that is heated with 199,000 BTU's. The system also provides domestic hot water by dumping cold water in the line to bring the temp down to an acceptable 120 deg. The problem is my monthly propane bills are typically around $1,000 per month in the winter and $800 to $900 in the summer to heat the water. (I set the tank temp down to 120 in the summer.)
My wife and I will retire within four years and, although we are not happy to replace relatively new HVAC equipment, we don't want to pay this exorbitant monthly cost to heat our house and water on a fixed income. We intend to replace the system before winter sets in. Average winter temps here are in the 40's with occasional dips into the low 30's and high 20's. Summer temps are typically in the 80's and 90's with occasional spikes to 100 & 104 degrees. I have 2 ton and 3 ton A/C units for summer cooling that struggle in the higher temps.
I received bids from three HVAC contractors to replace the system with 2 heat pumps and an alternative heat source as a backup. Two contractors (reps for Trane and Coleman) bid to install propane forced air units as the backup source. The third contractor (a Carrier rep) recommends a heat strip to replace the water coils in the existing air handlers. What are the pros and cons of each heat source system?
I also intend to replace the hot water tank with 2 tankless units -- Rinnai 94LSI or Navien 240A. The Navien stats are the most impressive but the company web site represents the parent company as a 33 year-old boiler maker in Seoul, South Korea that has been licensed in the US since 2003 trying to establish a market share here. It does not have a track record in the US to determine if there are service issues to compare with Rinnai. My e-mail to Navien/US asking about service issues has gone unanswered. Does anyone have experience with the Navien product?
Thank you for all information you may provide.