You put solar panels on the roof to generate energy from the sun. There are two types of panel: solar photovoltaic (PV), which generate electricity and solar thermal, which heat water. This guide focuses on solar PV
Solar panels don't need sunshine to work, just daylight, so you can still generate some electricity on gloomy days – important in a country with weather as dull.
PV roof tiles convert the light into electricity, which you can use to power your home during daylight hours. Any energy you don't use is pumped back to the grid. If you use more than the panels generate, the excess comes off the grid, exactly as it did before the panels were fitted.
In the winter, when solar power is less, you'll take more power from the grid. It's a good idea to set appliances to run while it's light outside, staggering them to max the savings.