An apparatus is provided for applying electromagnetic energy to an object in an energy application zone via one or more antennas at a plurality of modulation space elements (MSEs), in which each MSE may affect a field pattern excited in the energy application zone and is controllable by the apparatus. The apparatus includes a processor that determines an amount of energy to be supplied to one or more of the antennas at each of the plurality of MSEs, select at least one power supply protocol for each of the plurality of MSEs, in which at least two of the power supply protocols selected for different MSEs differ, and cause electromagnetic power supply to one or more of the antennas in at least a subset of the plurality of MSEs, based on the determined amount of energy and based on the selected power supply protocol.