Even at my low temperature setting I show that >95% homes call for heat much shorter than my system which leads me to believe that my statistics are lumped with homes with furnace while I have a boiler. This is true for all property choices (similar, apartment, all).
What does your System Type show on the Home card at the top of this page?
My steam boiler shows a similar runtime as yours @11 mins. Also > 96% of others. If you also have steam, I suspect it lumps us with forced hot water systems.
Giving it some more thought, I realize now that my conclusion is likely incorrect. Runtime Per Degree Day just shows how long it takes for the system to heat the space. Longer times vs others could mean few things:
boiler output is lower
radiator output is lower
system cut off point is too low (water in the loop is not hot enough)
circulation is too slow
and/or less insulation (higher heat loss)
Yes, all the things you mentioned could lead to longer run times. Sounds like you have forced hot water. Do you have a control on the boiler for adjustable water temp vs. outdoor temp or is it a fixed max temp (“system cut off point”)?