Due to a change in my home heating needs, I have spent the last week trying to optimize my hot water radiator system. If there's one thing to know if you have a modern condensing boiler, it's this graph: efficiency is higher at lower return water temps + running at low % of max.

My boiler was poorly configured and ran way too hot, leading to frequent on/off cycles.

Now it runs for hours at 20% of max and the house is incredibly uniform in temp with far less gas used. Yay!