Dennis,
Nobody has mentioned recovery rate which should be a key consideration. The tankless units have in effect an almost unlimited recovery rate but cost more and depending on the length of pipe run can cause some delay in delivering hot water to the tap. I took a different option and installed a 25 gallon Bradford White high recovery rate unit (83,000 Btu/hr) and never ran out of hot water. The unit cost around $1,100 or so installed. With the small tank, we could keep it at a much higher temperatue since there was a cold water cross-over to prevent scaulding. It was a gas unit but I am sure they could put smaller orifices on it to convert to higher heat content propane. There may be other brands besides BW that offer this type of unit but I can vouch for them. My new house has a 75 gallon propane unit that does not perform as well or as cheaply as the BW unit in my old house.
Nobody has mentioned recovery rate which should be a key consideration. The tankless units have in effect an almost unlimited recovery rate but cost more and depending on the length of pipe run can cause some delay in delivering hot water to the tap. I took a different option and installed a 25 gallon Bradford White high recovery rate unit (83,000 Btu/hr) and never ran out of hot water. The unit cost around $1,100 or so installed. With the small tank, we could keep it at a much higher temperatue since there was a cold water cross-over to prevent scaulding. It was a gas unit but I am sure they could put smaller orifices on it to convert to higher heat content propane. There may be other brands besides BW that offer this type of unit but I can vouch for them. My new house has a 75 gallon propane unit that does not perform as well or as cheaply as the BW unit in my old house.