Solar panels have gone from exotic to ordinary, but the way they work and, more importantly, the way they save you money is still widely misunderstood. Before deciding whether they are worth it for your home, which the is solar worth it guide tackles, it helps to understand plainly what the kit does and what governs how much you get from it.
How a panel makes electricity
A solar photovoltaic panel turns daylight directly into electricity. It does not need direct sunshine or heat to work, only light, so it still generates on a bright overcast day, just less than in full sun. Each panel produces direct current, the same kind a battery gives, which is no use to your house as it stands. So the second key component, the inverter, converts that direct current into the alternating current your home and the grid actually use. Panels on the roof, an inverter somewhere like the loft or a cupboard, and the wiring to tie it into your consumer unit: that is the heart of a system.
What the parts are
A domestic installation is a roof array of panels wired together, an inverter, a generation meter that records how much the system produces, and the connection into your fuse board. Many systems now add a battery, which stores surplus daytime generation for use in the evening, and that battery changes the economics enough to deserve its own treatment in the battery storage guide. The size of a system is given in kilowatts peak, its output under ideal test conditions, and a typical house array might be a few kilowatts peak across eight to sixteen panels, roof space permitting.
What governs how much you get
Output depends on things you can influence and things you cannot. Roof direction matters most: a south-facing roof generates the most over a year, east and west less but spread across morning and afternoon, and north-facing roofs are generally not worth it. The pitch of the roof, the absence of shading from trees, chimneys or neighbouring buildings, and simply how sunny your region is all play in. So does the season, with long summer days producing several times what short, low-sun winter days manage. A realistic expectation for the UK is a system that does well from spring to autumn and modestly in deep winter, not one that runs your house off-grid year round.
The part that matters: using versus exporting
This is the single most important idea for the money side. Electricity your panels make and you use yourself at that moment is worth the full price you would otherwise have paid to buy it, which is the expensive retail rate. Electricity you generate but do not use is exported to the grid, and you are paid for that export at a much lower rate. So the value of a solar system depends heavily on how much of its output you consume yourself rather than spilling to the grid. A house with someone home in the daytime, or with the dishwasher, washing and hot water timed to run while the sun is up, captures far more value than one that exports most of its generation while everyone is out.
Shifting your use to the sunshine
Because self-used power is worth so much more than exported power, the practical trick with solar is to move flexible loads into daylight hours. Running the washing machine, dishwasher and any immersion water heating in the middle of a sunny day, and charging an electric car then if you can, soaks up generation you would otherwise sell cheap and buy back dear. A battery does this automatically by storing the midday surplus for the evening peak. Either way, the aim is to consume your own sunshine rather than hand it to the grid for a pittance.
What to realistically expect
Solar is not a magic switch that ends your bills, and anyone promising that is overselling. A well-sited system meaningfully reduces the electricity you buy, most strongly in the lighter half of the year, and pays you a little for what you export. It works best as one part of a sensible whole, fitted to a home that has already done the cheap efficiency basics so the generation goes further. Understand it as a long-term reduction in your bills and a modest hedge against rising prices, and it makes sense; expect overnight independence and it will disappoint.