Every time your boiler runs, it blows heat out the chimney and it has
to heat up the pipes and the radiators before you feel any warmth at
all.
Heating all this metal, water and air costs money.
Over the last few years, radiator manufactures have made radiators
with less metal, holding less water to be most economic.
Cast iron radiators got left behind as they absorb so much heat and
cost more to run.
Perry