The invention relates to improved techniques for manufacturing power conditioning units (inverters) for use with photovoltaic (PV) modules, and to inverters manufactured by these techniques. We describe a solar photovoltaic inverter, comprising: a power conditioning circuit mounted on a circuit board, the power conditioning circuit having a dc power input to receive dc power from one or more photovoltaic panels and an ac power output to deliver ac power to an ac mains power supply; an electrically conductive shield enclosing said circuit board; and a plastic overmould over said conductive shield and said circuit board; wherein said electrically conductive shield has one or more holes to allow said plastic overmould to extend through said shield to cover said circuit board.