How Solar Panels Generate Electricity
Solar photovoltaic (PV) panels convert sunlight directly into electricity using semiconductor cells. When photons from sunlight strike the cell, they release electrons that flow as direct current (DC). An inverter converts this to alternating current (AC) for use in your home. The amount of electricity generated depends on panel efficiency, the size of the system measured in kilowatt-peak (kWp), the orientation and pitch of your roof, shading, and the amount of usable sunlight hours at your location.
Roof Suitability for Solar Panels
South-facing roofs at 30 to 40 degrees pitch are optimal in the UK, producing the most generation annually. East and west-facing roofs produce approximately 15 to 20 percent less but can still be viable, especially with battery storage. North-facing roofs are not suitable. Shading from trees, chimneys, or neighbouring buildings significantly reduces output and should be evaluated carefully. A structural survey is recommended for older roofs before installing panels, as the additional weight requires adequate support.
Estimating Energy Savings
A typical UK home uses between 2,900 and 3,500 kWh of electricity per year. A 4 kWp solar system in the south of England generates approximately 3,400 kWh annually, while the same system in Scotland generates closer to 2,800 kWh. Self-consumption — using the electricity you generate rather than exporting it — offers the greatest financial benefit. Shifting energy-intensive activities like running washing machines and dishwashers to daytime hours maximises the value of your solar generation.
Solar Panel Payback Period
The payback period for a solar installation depends on system cost, energy prices, your rate of self-consumption, and any export tariff you receive for selling surplus electricity back to the grid. With rising electricity prices, most UK households now see payback periods of 7 to 12 years on a well-sited system. After payback, the system generates essentially free electricity for the remainder of its 25 to 30 year lifespan. Battery storage can improve self-consumption and reduce payback time if you have high daytime generation but low daytime usage.