A big drawback with installing solar PV systems to generate electricity is the limited ability to store surplus energy for use at a later data. Battery technology is currently a hot bed of development and Tesla have beaten most competitors to the market with the launch last year of the Tesla Power Wall battery. Designed to work directly with solar PV systems, each unit can store up to 14 kWh of surplus electricity and costs approximately £6,500 to install. A standard 3 bedroom house with one Power Wall unit linked to a 4 kW solar PV array would generate and store enough electricity for 75% of daily demand. A 10 kWp and two Power Walls would make the house completely independent of mains electricity. See more details at: https://www.tesla.com/en_GB/powerwall