If you’re thinking of generating electricity using a renewable energy source, then photovoltaic cells are an option. Fitted onto the roof in the form of tiles or panels, photovoltaics generate electricity using sunlight. Under lab conditions, 8m² of photovoltaic tiles produces around 800kWh off electricity a year, and in situ they will produce less. The average UK home uses around 6,000KWh a year. A PV panel roof can cost around £12,000-£14,000.