Theoretically, if it takes a longer time to heat up, the latent heat in the radiators should allow it to cycle less frequently, so the total time of operation would be about the same. But if the boiler or radiator sizes are too small, then it will run for a longer time in order to try to catch up with the heat loss. In that case, either system will run the same, namely too much.
: I have one of my rare questions I need a answer to,from someone in the business.
: Lets say you have hot water heat,with radiators. I understand some people prefer this over baseboard due to the fact you get residual heat from them for a period of time,where you don't baseboard. My question is,because a radiator type system uses such a larger quantity of water,thus longer running time to heat the water to supply the heat to the house,is this actually an economic way of heating,over baseboard. It would seem that if sufficiently insulated,baseboard would be the way to go. I ask this because my daughter owns a small,2 story cape,50 years old,but upgraded with new insulation, with rads. I can't remember the BTU's(at least a 100 thou anyway) but we installed a new boiler last year,and it's much better than the old one,but still seems to run for a very long time. There are a few smaller rooms in the house that get extremely warm. Is there any reason we couldn't switch rads for baseboard in those rooms? Two of them being small baths,and a spare bedroom that is used more as a catchall then anything. Just seems like an awful waste of fuel to run so long. I know you can adjust the flow to the rads,but I'm looking for all around less water usage. Any opinions on this?