

It’s terribly inefficient. The efficiency is lost when the steam that condenses back into hot water is lost and none of it is returned to the boiler to be reheated. Rather than reheating this returning water which normally is at 120-160 degrees Fahrenheit, fresh water is used which in the winter here is around 56 degrees. Aside from this the cold water taken in contains impurities such as dissolved gasses which cause corrosion and dissolved minerals which can cause scaling that acts as an insulator raising the amount of energy needed to heat the water.
I can’t speak for NY but that is the situation in Cleveland. I have a customer downtown on city steam. I watch hot water discharge to a drain at the rate of about 3 gallons a minute and there’s 1440 minutes in a day. When it was built I’m sure they reclaimed most of it (80% return is considered good) but over time the pipe corrodes and you have leaks.