Replace radiator mains and reduce electrical consumption
1> install a constant delta-P pump ERP rated circulator (it'll adjust the power to the required delta-P instead of running fixed RPM)

2> install constant-delta-P thermostatic preregulation valves (Caleffi Dynamical)

3> Calculate each valve maximum flow allow no more than the needed flow to heat each room

This configuration can let your (GAS) consumption go down by at least 10% if you have a condensing boiler and you set properly the delta-T, also can push down the electric consumption by about 40% or more (up to 95%), (Pump will run maximum just for the first hours, when valves start to throttle down radiator flow, pump 'reads' less need and slows down it's speed accordingly, pumps are also  'intrinsically' much more energy efficient (EEI&lt;0,23 when older 'A-class' had EEI of about 0,40)

Similar configuration may be achived (knowing diameters and lenght of each pipe) using delta-p compensation before zone valves and using 'standard' preregulation valves on radiators (But in this case, calculating each valve is much more difficult, with dynamical calculation is quite easy)

This is a reference for dynamical (it's in Italian, but I think google can help translating)
Another reference (see summary: blue box on page 29)
ERP-related (1) 
 ERP-related (2) information (English)