What size solar panel system do you need?12-01-2018 Back
You’ve made the decision to install a solar panel system on your home, but you’re not sure how big it needs to be. Should there be enough panels to fill the whole roof? Will having too many panels damage the roof and lead to expensive repairs?
How big is a solar panel?A solar panel is made up of a series of small photovoltaic (PV) cells wired together. Most domestic systems use solar panels that have 60 of these cells. The full system (known as an array) will be made up of a number of solar panels, typically placed next to one another.
There are many brands of solar panel, and each brand is slightly different in size. However, on average, one standard solar panel will be approximately:
1,650mm (length) x 990mm (width)
1.65 metres x 0.99 metres
1.63 square metres (m2)
At YES Energy Solutions, we offer two types of solar panel, depending on the system you choose.
• Our standard array uses the Vikram Eldora Ultima 250W polycrystalline panel, which measures 1,640mm (length) × 992mm (width) × 40mm (height) (or 1.63m2)
• Our deluxe array uses the SolarWorld 280W monocrystalline panel, which measures 1,675mm × 1001mm × 33mm (or 1.68m2)
How many panels do I need?The number of solar panels you need ultimately depends on how much electricity you want to generate.
Most domestic systems have a capacity of between 1 kilowatt (kW) and 4kW. Larger capacity systems are more productive—and will save you more money—so you should get the biggest system you can for your home.
Our guide to energy production explains capacity and the output of solar panels in more detail.
How much roof space do I need?Most homes in the UK have roofs that can accommodate solar panels. However, if your roof has a window, chimney or vertical flue, for instance, this could reduce the amount of space available for solar panels. And these features could also cast shadows on the panels, making them less efficient. Furthermore, other factors such as the angle and direction of the roof will influence whether fitting a system to your property is worthwhile.
For an idea of overall size, a 1kW system consisting of around four panels will typically take up around 8m2 of space. A 4kW system made up of around 16 panels would need roughly 28m2 of space. Bear in mind that some brands of panel have a larger capacity so may cover a smaller area of roof space.
What does a solar panel system weigh?It’s important to know how heavy a system of solar panels will be so you can make sure your roof is strong enough to support it.
As with size, there will be some variation between brands as to the weight of a single panel. The standard 60-cell solar panels used most often in residential systems weigh around 18–20kg. The Vikram Eldora Ultima and SolarWorld panels YES Energy Solutions use weigh 18.5kg and 18kg respectively.
If we use the SolarWorld brand as an example, this means that the 16 panels needed for a 4kW system would have a combined weight of 288kg. As this system fills roughly 28m2 of roof space, that gives a weight per square metre of 10.3kg. Most homes have roofs that can easily support this weight, although an installer would determine this—and whether any work is needed to strengthen the roof—as part of their initial inspection.
How should solar panels be angled? What direction should they face?In the UK, most homes have roofs that are angled between 30 degrees and 45 degrees, which falls within the Energy Saving Trust’s guidelines for best overall performance. This is because the UK’s latitude (its point on Earth in relation to the equator) is 51 degrees north, meaning the sun is always south of your house and never goes directly over it. It’s why putting panels on a north-facing roof isn’t recommended, and why there should be nothing obstructing or casting shadows on the panels.
What about flat roofs?Solar panels can work just as well on flat roofs, as they use special mounting frames that allow them to be tilted at the best possible angle. There are added benefits, in that flat roofs:
• are easier to access, making installing and maintaining panels much easier
• do not need tiles taken up
• make the panels less visible from the street
How are solar panels installed?Installing a solar panel system is easy (for the professionals, anyway!) and shouldn’t cause much disruption. Though the panels are usually mounted on the roof, it’s possible to install them on the ground or fix them to a wall, and an installer will be able to advise you on the best place for your system.
Roof-mounted panelsIf you’re having solar panels fitted to your roof, the installer will probably need to put up scaffolding and so you must make sure they have the space to do so. Before they do any work, however, the installer will come out to inspect your roof (including the loft) and confirm that it has the strength to support the weight of the panels. They will also check that your electrics are in proper working order for the panels to function.
First, the installer will attach special hooks to the rafters of the roof. They’ll likely need to remove some roof tiles or slates to do this, but they’ll replace them afterward (and make sure everything is watertight). They’ll then fix the frame of the panel to those hooks, then clamp the panels to the frame.
Once the panels are mounted, the installer will wire them to the inverter. Solar panels capture sunlight as a direct current (DC) which needs to be converted to an alternating current (AC) to be used as household electricity. The inverter is the device that does this job, and will be placed somewhere inside your home. The installer will then connect this device to the electricity grid.
Ground-mounted panelsIf your home isn’t able to accommodate roof-mounted solar panels (e.g. because of the angle or direction of the roof or weakness in the structure), you could consider a ground mounted system. Like those used for flat roofs, the panels are fixed to a frame and tilted to the ideal angle. Some specialist models can be adjusted so you can move them throughout the year as the position of the sun changes with the seasons.
Ground-mounted systems have the benefit of being really easy to install and very efficient in their output, as they aren’t burdened by the angle and direction of the roof.