What does kWp mean?
kWp, or kilowatt-peak, is the maximum output of a solar panel system under standard test conditions. It is how systems are sized and compared. A 4 kWp system will rarely produce exactly 4 kW at any moment, but kWp lets you compare quotes and estimate yearly generation on a fair basis.
How do I work out how much electricity I use?
Find your annual electricity use in kWh on your bill or in your supplier's app. Use a full year's figure, because Scottish homes use noticeably more electricity in winter. This number is the starting point for sizing panels and deciding whether a battery makes sense.
Think ahead too. Working from home, buying an electric car or switching to a heat pump will all increase your electricity use, and it is easier to plan for that now.
How many solar panels will fit on my roof?
Modern panels are typically around 1.7 to 2 square metres each. After allowing for roof edges, chimneys, roof windows and vents, many houses fit somewhere between 8 and 14 panels on a suitable roof face. Your survey will confirm the exact layout for your home.
If your main roof is small or shaded, panels can sometimes be split across two roof faces or placed on a garage or extension.
What size system suits a typical Scottish home?
Many Scottish homes suit a system of around 3 to 5 kWp, which is usually 7 to 12 modern panels. Smaller terraces and semis often sit at the lower end. Larger detached homes, farmhouses and homes with an electric car or heat pump may benefit from more.
The right size balances roof space, your usage and your budget. A larger system is not automatically better if most of the extra electricity would simply be exported.
How do I estimate how much a system will generate?
Multiply the system size in kWp by a local yield figure. In much of Scotland a rough guide is around 850 to 950 kWh per kWp per year for a well-placed roof, so a 4 kWp system might produce roughly 3,400 to 3,800 kWh. Your survey estimate will reflect your actual roof.
Roof direction, tilt and shading all change the figure, which is why a proper estimate should always be based on your own property rather than an average.
Should I size up for a battery or an electric car?
Often, yes. A battery lets you use more of what you generate, so a slightly larger array can make sense. If you plan to buy an electric car or install a heat pump, mention it at survey, because sizing for future use is usually cheaper than adding panels later.
Larger systems may need approval from your local network operator, SP Energy Networks or SSEN, before installation. We handle this application as part of the process.