Roof Suitability For Solar Panels (Guide)

Overview: Is Your Roof Suitable For Solar Panels?

Our guide to the most suitable roof layout for solar panels is a 10-minute read. Strapped for time? Bookmark this guide for later, and read this quick-fire overview instead…

Roof pitch is incredibly important. Typically, the sweet spot and best angle is 30°. If your roof is pitched at 30° and facing due south, you’ll get the highest production from your solar panels possible. 

That said…you can install solar panels on a flat roof. 

In some cases this is actually the better option. Why? With adjustable mounts, you’ll be able to change both the angle and direction your panels face, improving their electricity production in the process.

Of course, any shade from neighbouring buildings, trees and hedges is all going to have a bearing on how efficient your solar panel system is. The best roofs for solar panels are those that have no shading, especially between 10am-4pm. 

Your roof doesn’t just need to be facing the right direction and at the right angle, they need to be the right size, and be in reasonable condition. Typically, you’ll want a roof that’s got 20sqm of free space for a 3kW system, and is still new (and strong) enough that it can hold a system that weighs 300 kg or more!

And finally, you won’t need planning permission for an average solar panel installation thanks to permitted development laws. However, if you plan a large-scale commercial installation, it’s worth checking with your local council to see if you need planning permission.

Use our clickable tool here. Type in your postcode and our tool will determine the angle, orientation and suitability of your roof for solar panels. 

Or, if you have any questions about your roof’s suitability, contact our experts here. 

Guide: Roof Suitability For Solar Panels

Below, we’ll cover the most important factors to consider when determining if your roof is suitable for solar panels.

Best Roof Angle For Solar Panels

In order to maximise electricity generated by solar panels, the ideal roof space will have an angle or pitch of 30°. 

A PDF produced by the Energy Saving Trust shows the difference in electricity produced, based on the percentage of ideal annual output you'll get, when using different orientation and tilt angles: 

As you can see, there’s a reasonably large range of solar panel angles that work effectively. 

If we look at a roof that is facing exactly south, you’ll be able to achieve over 90% efficiency on roof pitches of anywhere from 0°-30°.

In the example of a roof facing exactly south, the perfect roof pitch in this scenario is 30°, producing 100% efficiency. A roof with a pitch of 60° would see a drop in electricity consumption of 13%, as it would only be 87% efficient.

Find out the pitch of your roof and potential energy savings by using our clickable solar panel tool here. 

Our tool can scan any property’s roof in the UK, so you can find out your roof angle by searching your postcode, and its suitability for solar panels.

Roof Orientation For Solar Panels

Roof orientation, or, the direction in which your roof faces is also important. As we’ve mentioned above, the perfect scenario here is a roof that faces exactly due south. 

However, that’s not to say that if your roof doesn’t face exactly due south, that it’s not worth investing in solar panels.

Using the chart above, we can see solar panels installed on a roof facing west or east sit in the range of 78%-93% efficiency when installed on a roof with an angle of 30°. 

The only scenario where you wouldn’t see a good return on investment is on a roof that’s facing due north. But, if you do have a roof that’s facing due north it’s because it’s a:

• Flat roof that absorbs solar energy from all angles, so still would be suitable
• Pitched roof on one side of your house, which means the other side of the property is where you’d want to install your solar panels

Our solar panel installation tool allows you to scan your roof to determine its orientation and potential cash savings you could see from solar panels. Simply type in your postcode and our clickable tool will do the rest!

Shading

It goes without saying that solar panels need light and sun in order to produce electricity. The more hours of daily sunlight your roof gets, the better. 

This is limited by where you live, as different areas of the UK have different levels of daily sunlight hours. More importantly, objects that create shade need to be taken into account. 

The highest production of solar electricity takes place between 10am-4pm. Obviously this varies depending on the month of the year, but typically, these hours are the strongest for sunlight.

You'll want to ensure that shading during this period is limited. Objects that can shade your solar panels and reduce their efficiency include:

• Neighbour's properties
• TV aerials
• Trees and hedges
• Chimneys
• Garages, sheds and vehicles (when solar panels are installed on a single storey flat roof)

You’ll want to ensure that the location of your solar panel installation is subjected to as little shade as possible, especially during the hours of 10am-4pm.

Shading of one or more of the panels can impact the rest of the panles in that string, as each row of panels are set as a series. If one is only producing 50kWh, instead of 350kWh, because it is shaded, then the rest of the panels in that series will also only produce 50kWh. This can be resolved using either micro-inverters or DC optimisers, but this adds cost to the install.

Roof Construction & Condition

A roof constructed with asphalt shingles and still within manufacturers’ / homebuilder’s warranty is the best type of roof to install solar panels on. 

Asphalt shingles are a strong type of roof tile. Given the average solar panel weighs around 20 kg, your roof will need to be strong!

A typical 3.5kW solar panel system will have 10 panels. Alongside the frame and fixings to mount the panels, the overall weight your roof will be subjected to, could easily surpass 300 kg. 

Other types of materials that solar panels can be installed on include the likes of: traditional shingle tiles (not as strong as asphalt), metal, and of course tar / gravel (typical on flat roofs such as on a single storey extension). 

Alongside the roof’s construction, a reasonably new roof still under manufacturer’s warranty is ideal. An old roof that isn’t under manufacturer’s warranty may see its integrity compromised when you install a 300 kg+ solar panel system on it. 

Not sure if your roof can take the weight of solar panels safely? Ask one of our solar panel experts here. 

How Big Does My Roof Need To Be?

For your roof to be suitable for solar panels it doesn’t just have to be strong enough and facing in the right direction, it needs to be big enough too. 

A typical solar panel is approximately 1.5m x 1m. For a 3kW system, you’d need approximately 10 panels meaning a 1.5 sqm of space per panel, or 15 sqm of roof space in total. 

However, that doesn’t account for spacing between panels, as well as space needed for each panel mount. So, a roof for 10 solar panels needs to be around 20 sqm in total. 

A 3kW solar panel system such as this is going to be suitable for a 3-bedroom semi-detached house. The average 3-bedroom house in the UK is going to consume approximately 2,700kWh of electricity per annum, which a 3kW system should easily be able to produce.

Still not sure what size solar panel system you need and how big your roof needs to be? 

Jump over to our page covering how many solar panels you need here, or use our solar panel configuration tool here. 

Can I Install Solar Panels On A Flat Roof?

You can install solar panels on a flat roof. This is an ideal solution for those that have a pitched roof that isn't suitable for solar panels due to: 

• Not being big enough (a typical 3kW system is going to need about 20 sqm of roof space)
• Facing in a direction that doesn't get many daily sunlight hours (ideally you want a roof facing due south, anything other than this will decrease electricity production)
• Is shaded by objects such as TV aerials, other buildings or trees (any shade during daylight hours will reduce electricity production massively)

Like any installation, you'll need to check that your flat roof can support the weight of solar panels; typically around 300 kg for a 3kW system that's suitable for a 3-bedroom semi-detached house. 

Unlike pitched roof setups, installing solar panels on a flat roof means:

• Maintenance is going to be cheaper; flat roofs are easier to access than pitched roofs
• They won't be visible from the road to passers by
• If you buy specialist mounts, you'll be able to adjust by the angle and orientation of your solar panels for maximum efficiency

As you can see here, using a flat roof for solar panels certainly isn’t a bad idea. In fact, it’s favourable for many properties that aren’t facing due south, or don’t have a pitched roof that’s exactly 30°. 

Efficiency levels even when set at 0° sit between 87%-93%, and this can be further improved if you use mounts whereby you can adjust both the angle of the solar panels and which direction they’re facing.

Not sure if your flat roof is suitable for solar panels? 

Speak to our solar panels experts here, they’ll be able to design the most suitable solar panel system for your property, and help you choose between a flat roof and pitched roof setup.

Do I Need Planning Permission?

If you plan to install panels on a pitched or flat roof, you’re unlikely to need planning permission as they fall under permitted development rules in the UK. 

Typically, both commercial and residential properties won’t need planning permission if their system is unlikely to produce less than a megawatt of electricity per year. 

And the UK government is constantly relaxing planning laws when it comes to solar panel installation, to fast track towards their net zero target. 

However, if you’re planning to install solar panels on a large scale and they’ll be ground mounted, it’s worth contacting your local council before making a sizable investment in solar panels.

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