PV in solar panels means ‘photovoltaic’, because the panels consist of small photovoltaic cells that are connected together. PV cells are made out of semiconducting material — silicone being the most commonly used. PV cells are usually very small but when combined together to form solar panels and solar arrays, they can be very efficient. When the sun shines over the cells, an electric field is created. The stronger the sun, the more electric energy is produced. Nevertheless, the cells do not need direct sunlight to work, and they can still produce electricity on a cloudy day. PV panels are available in various shapes and sizes and can be easily mounted on top of an existing roof.