% Savings Steam versus modulated hot water

Steve Garson

This is a repost with a different twist:
I have a 70 year old Burnham Steam Boiler with modern oil burner. I burn around 1100 gallons a year. The steam heat is even and the water loop makes no noise. In short - it works fine, although I seem to be adding a lot more feed water this winter. The boiler heats the thin tube radiators with steam and a room with 30 feet of baseboard. I also have a master suite heated with radiant floor through a Bradford-White water heater.

If I replace the steam boiler with a modern boiler, installation costs will be lower, but steam is not as efficient as water. Anyone able to help me with this?

Converting to water, I would use the same radiators, but installed new feeds and returns. I could also move the radiant to a more efficient boiler and leave the water heater for just the domestic HW.

Without consideration as to the cost of installing one approach versus the other:

Does anyone have a sense of what % savings can be expected so I can make a well informed decision?