Solar panels (also known as photo voltaic or PV) generate energy from the sun. They can be placed on a roof or within a garden. Their orientation will affect how much sun they get, and how much energy you can get from them. They work by using layers of semi-conducting material which generate a flow of electricity when the sun shines on them.
In the vast majority of cases your home will need to remain connected to the grid to provide you power at times when your solar panels can’t provide it, such as the evening. Since they need to be set up this way, your solar panels won’t work If you have a power cut.
Alongside the solar panels, an inverter is used to convert the energy into a usable format. The inverter converts the power from your panel to make it suitable for your household appliances (they convert the energy from from direct current, or DC, at the solar panel to alternating current, or AC, in the home). If you have a few solar panels (an array) it may be worth looking at getting optimisers or micro inverters to ensure that you get maximum energy from them, especially if you think one or two of them might be in shade at times. It's also worth looking at keeping any nearby trees trimmed so they don't cast shadows on the panels.
Installing batteries alongside your inverter will allow you to save any excess energy generated during daylight hours for use at other times. The inverter can also be easily configured to draw energy from the grid overnight during 'off peak' hours, and storing this in the batteries for use the next day. In order to benefit from lower electricity prices overnight, you will need to be signed up to a variable tariff with an energy provider and this can be as low as 7p/kWh.
The Energy Saving Trust give a great overview of solar panels including some guidance on planning permission and a calculator to give you an idea of the benefits you might see from installing a solar PV system.
If you don't have batteries, using the energy from your panels comes down to knowing when your home will be busiest and when you’ll get most benefit from them. If there are a few of you in the household and you’re around most of the day, for example - working from home, you will find it easier to use the energy generated (make hay while the sun shines).
It’s much better to use as much of the energy generated at home, rather than sell it back to the grid. The pay back from the ‘Smart Export Guarantee’ (currently around 5p per kWh) is greatly outweighed by the cost of purchase (28p+ per kWh during most of the day and rising). Ways to ensure you use as much as your solar energy as possible include storing the energy in hot water, or storing it in a specially designed battery or an electric vehicle (EV).