Solar panels are a popular choice for homes and businesses looking to reduce their energy bills, but for some buildings, they deliver a better return than others. So, can you put solar panels on a flat roof in London and reap the rewards of solar power?
- Yes, solar panels can be installed on flat roofs
- It’s often easier to put solar panels on flat roofs than it is to put them on sloped roofs
- Can be cheaper to put solar panels on a flat roof due to easier installation & fewer labour costs
Throughout this blog, London Property Services’ flat roof specialists answer all the key questions about solar panels on a flat roof in London, enabling you to decide whether it’s a worthwhile investment for your property.
Are solar panels on a flat roof as good as those on a sloped roof?
They certainly can be. It all comes down to how they are installed. Solar panels laid flat won’t deliver the types of efficiency you’d be aiming for. Tilt the panels slightly by placing them on angled mounts, and they provide similar or even better performance than solar panels on sloped roofs.
Do solar panels on a flat roof work differently?
Not really. Solar panels capture sunlight and convert it into electricity. You’ll then use this energy to power your home. You can bank it in the battery and then sell it back to the National Grid through the SEG (Smart Export Guarantee). This is exactly how solar panels work on both flat and pitched roofs.
You’ll see the only real difference in how they are mounted. On pitched roofs, solar panels are positioned at an angle, whereas on flat roofs, they can be completely flat or tilted.
Will I need planning permission to put solar panels on a flat roof?
No, planning permission is no longer required if you wish to add solar panels to a flat roof. Since changes made in 2023, the addition of solar panels to a roof like this falls under permitted developments. This means you can make the change without having to seek permission.
However, some building types or modifications are exempt. You won’t be able to install solar panels on your flat roof if:
- The property is a listed building
- The solar panels will be at least 60cm higher than the highest part of your roof, excluding the chimney.
- You live in a flat
- You live in a conservation area
- You don’t have enough space for a 0.5m-1m border between the solar panel system and the edge of the roof
Are solar panels expensive to install?
It depends. In some cases, installing solar panels on a flat roof can be cheaper than installing them on a sloped roof. The quicker and easier installation results in fewer man-hours, translating to less expense. However, in some cases, solar panels installed on a flat roof can be more expensive than if they were installed on a sloped roof. This is because you’ll need a special mounting system to angle the panels correctly, and that won’t be free.
The Federation of Master Builders states that installing a solar panel system on a flat roof could cost anything from just over £5,000 to more than £14,000, depending on the size of the property and the number of panels required.
How much money will solar panels on a flat roof save me?
It depends. Your energy consumption, property size, current energy costs and whether you have a SEG tariff will all determine how considerable the savings might be. A SEG tariff enables you to sell stored energy back to the national grid.
It is quite possible to save in excess of £1,000 per year on energy costs in larger homes, whilst smaller properties that consume less electricity could see annual savings of close to £400. Overall, this gives a typical break-even point of around 10-13 years.
What kinds of solar panels are best for a flat roof?
When you add solar panels to a flat roof, it is best to install them at an angle to deliver enhanced efficiency. Having them lie flat will work, but the returns will be much smaller than if they were mounted.
There are a few options available for mounting solar panels on a flat roof. Each has its benefits and drawbacks.
Ballasted south-facing
If your solar panels are installed on a south-facing mount, they will be laid out on a frame with large gaps between the rows to prevent shading. Ballast is then put underneath the panels for the same purpose. They deliver excellent efficiency, but you’ll be limited by the number of panels you can fit due to the gaps each row requires.
Furthermore, with a significant amount of ballast being required, the roof can be put under additional strain, resulting in it getting damaged and requiring the care of a roofing specialist.
East/West mounting
Whilst not as efficient as the south-facing mounting system, an east/west set-up can be a good option. The panels are fitted back-to-back with one side facing east and the other facing west. Due to this positioning, less ballast is needed, resulting in less strain on the roof. Additionally, the efficiency reduction is easily mitigated as you can fit more panels on a roof with an east/west system than on a south-facing mount.
How much will the weather affect the solar panels on my flat roof?
In the UK, our weather isn’t normally extreme enough for your solar panels to be significantly affected. However, should there be higher-than-normal temperatures or tropical storm-like winds, you may notice that the performance and/or stability of your solar panels starts to be affected.
Extreme heat
If the warm weather is unusually hot, your flat roof will likely benefit and store plenty of energy for you. However, as temperatures rise, the resistance in the solar cells increases. This can make it harder for electricity to flow and, therefore, make it more difficult for the panel to deliver the energy you’d expect.
Rain
We can always expect rain in London, but you shouldn’t have to worry about what it may do to your solar panels. If your solar panels are mounted, the rain acts as a cleaner, clearing them of dirt and debris and making them more efficient. If the panels are flat, the water will pool, rather than flow off the panels, and not clean them effectively.
Wind
We don’t tend to experience tropical storms in London, meaning the wind speeds are unlikely to pose a huge risk to your solar panels, but the risk should still be considered. Wind can get underneath the panels on a flat roof, potentially lifting them away. This is especially common for those on angled mounts, whereas solar panels bolted directly to the flat roof may be a little more resistant to the high-speed winds.
Snow and ice
The flatter the angle of the solar panels, the more likely they are to suffer a buildup of snow or patches of ice.
Pros and cons of solar panels on a flat roof
As with anything, there are advantages and disadvantages. Solar panels on your flat roof are no different. From energy saving to roof damage, there is plenty to weigh up before making a decision.
Advantages of solar panels on a flat roof
- Easy to clean
- More discreet
- When mounted, easily removable
- More affordable to install than on a sloped roof
- Easy access for repairs and maintenance
- Easy to install
Disadvantages of solar panels on a flat roof
- Heavier than a standard system due to the mount
- May lead to increased risk of roof leaks due to pooling water
- Ballasts can lead to increased costs
- May require more cleaning if not pitched
- May require more space for optimal results
At London Property Services, our skilled and experienced London roofers are on hand to provide round-the-clock repairs and maintenance to homeowners and businesses throughout the city. Contact us to find out more about our roof repair and solar panel installations.
