Looking to replace water heater with a new indirect model, either superstor or triangle tube and trying to make the best decision on sizing the unit for my home. Currently have a oil fired peerless boiler with output of 119,000 btu to feed the unit and have a home of 5 people that need to shower, wash dishes and perform laundry during the day. When performing the calcs I cannot seem to determine which would be more efficient, a smaller unit such as a 30 gallon which falls within the btu input requirements for the boiler but is on the verge of the first hour rating (which I estimate requiring 180 to 200 gallons) or increasing to a 45 - 50 gallon unit which exceeds the first hour rating requirement but is oversized for the boiler. Would the purchase of a larger unit be a waste of money or would it be better to have a larger unit for the water storage with the understanding that the boiler would need to run more to keep up with the unit.
Any input would be great appreciated
Any input would be great appreciated