I have a question about replacing my old boiler and hot water tank. Our boiler is original to our house (mid 80's) the hot water tank is under 10 years old. We have gotten 2 quotes for an high efficient boiler and indirect water tank. Both are at opposite ends of the spectrum. The first is for a Burham Alpine 105 with 105,000 BTUH input and a SSU45 Superstor and the second is for a Burham Alpine 150 with 150,000 BTUH input and a SSU80 Superstor. My question is do we need an 80gal tank? is 45 to little? We have gas heat. 4 zones. Our house is about 2500sqft with 3 1/2 baths. We have not done a heat loss yet. Do you have any thoughts? Our old system is an old Burnham boiler with a 40 gal tank. We have 2 adults and an infant presently living in the house.