How solar panels work on a UK home

Photovoltaic cells in each panel produce direct current when daylight falls on them. The panels are wired together into one or more strings and feed an inverter, which converts that direct current into the 230V alternating current your home uses. The output joins your consumer unit and supplies whatever the house is using at that moment.

Anything you do not use flows out to the grid, and anything the panels cannot cover is imported as normal. The changeover is automatic and continuous — there is nothing to switch.

• Panels — rated in watts each; several make up the kWp figure for the system.
• Inverter — converts DC to AC; a hybrid inverter can also manage a battery.
• Optimisers or microinverters — manage panels individually, useful with shading.
• Isolators and protection — allow the system to be shut down safely.
• Generation meter or monitoring — shows what the system produces.
• Smart meter — usually needed to measure and pay for exported electricity.

Panels respond to daylight, not heat, so they generate on overcast days, just less. UK output is strongly seasonal, with the bulk of annual generation arriving in the lighter half of the year, which is why annual figures are more meaningful than daily ones.

In a power cut a standard grid-connected system shuts down for safety, so it will not power your home unless it has been specified with equipment designed for backup supply. If that matters to you, raise it with installers early — it changes the specification.

Typically a survey, a design and quotation, notification or approval with the local network operator, scaffolding, the physical install over one or more days, commissioning and certification, then setting up an export arrangement with a supplier. Your installer should tell you which certificates and warranties you will receive and who to contact for aftercare.