Your boiler's flow temperature determines how hot the water it sends to your radiators is. You can usually adjust this on the boiler's control panel, often using buttons or a dial labelled with a radiator symbol. Check your boiler's manual for specific instructions, as models vary.
Lowering your boiler's flow temperature by a few degrees can help you save money on your heating bills. Be careful not to set it too low, however, as this can reduce the efficiency of your heating system, leaving your home feeling cold and potentially increasing the risk of condensation and damp.