A corona igniter (20) includes an ignition coil (26) providing a high voltage energy to an electrode. The coil (26) is disposed in a housing (34) and electrically isolated by a coil filler (36) and a capacitance reducing component (38) which together improve energy efficiency of the system. The coil filler (36) includes an insulating resin permeating the coil (26). The capacitance reducing component (38) has a permittivity not greater than 6, for example ambient air, pressurized gas, insulating oil, or a low permittivity solid. The capacitance reducing compound (38) surrounds the coil (26) and other components and fills the remaining housing volume. The coil filler (36) has a filler volume and the capacitance reducing component (38) has a component volume greater than the filler volume.