Ideally, the power (or kWs) should be slightly over the maximum required kWs calculated for the system. If the boiler is oversized we can adjust the output to suit your particular project. For example a 28kW boiler is very common, but your home may only need 14kW of heating. We would adjust the boilers settings to run at about 16kW that way you are not using excess fuel.
What size boiler should I have, and what happens if the boiler power exceeds system needs?