Over recent years rooftop solar has proved to be one of the most cost effective and popular choices by businesses in terms of renewable generation.
Not only does it demonstrate a businesses’ green credentials, but it makes sound financial sense in taking a step towards reducing energy bills and transitioning to becoming a net zero business.
At the start of 2025, the UK has 18 GW of solar power deployed and in 2024 more than half of the UK electricity generation came from renewables, helped by a record-breaking year for solar. However, we have some way to go to meet the government’s ambitious targets of 81% reduction in emissions and 70 GW of deployed solar generation by 2035 – this would be a fourfold increase in the current solar capacity over the next ten years.
That said, we are going in the right direction, with more businesses investing in renewables and the introduction of enticing funding solutions and PPAs, allowing businesses to pay for solar energy generation at a much-reduced market rate, without the need for large upfront investment.
Schools, warehouses and car parks could be at the forefront of the solar revolution but helping to shine a light on what types of businesses may be ideal for solar (and the funding that comes with it) is David Woon, Net Zero Engineering Design Manager from leading Net Zero and Renewable Technologies Consultancy, Ennovus Solutions.
We asked David about what the perfect business for rooftop solar looks like and the pitfalls to look out for when seeking a partner to design and install it.
David, what sort of buildings would be your ideal project for rooftop solar?
Contrary to belief, any building with roof space can work, if designed and installed in the correct way. It is important to remember that each building is different, with a different energy requirement, and therefore a solar array should be designed specifically for each business – it isn’t necessarily a one solution fits all.
In our experience, building types that yield the highest energy and carbon savings are high energy users with a large building footprint such as manufacturers, leisure centres, swimming pools, and hotels outside of the city centre.
A common misconception is that you should avoid solar if your roof is made from certain material, but this isn’t always the case. There are of course roof types and coverings which naturally lend themselves well to the most cost-effective installations, such as low profile metal trapezoidal sheet roofs or flat roofs with a membrane covering; however, even slate roofs, which are sometimes avoided due to their fragile tile type, can still present a very good opportunity.
Before the installation on any roof, regardless of its age or visual condition, a structural survey will always be required. If a roof space has deteriorated or if there is significant damage, then a roof condition survey (both pre and post installation) can be recommended for added peace of mind.
What hurdles do businesses encounter when looking to install rooftop solar?
It is important that each step from the initial engagement through to the final commissioning is taken with care. As roof mounted solar is a construction project, all installations should also follow the CDM2015 regulations, which unfortunately doesn’t always happen within the industry.
Cost is often the biggest barrier, despite a well-designed solar array often having a payback period of less than 5 years (I’d say that is pretty good for a 25+ year asset lifespan); however, from a technical viability, the biggest hurdles to overcome are often the pre-installation compliance. These fall into three categories:
- Grid Approval: Any installation greater than 16 A per phase (for a three phase system, this is equivalent to 11.04 kWp), will require a G99 application to the local distribution network operator, or DNO. This application ensures that the solar array can be safely connected to the existing network, and approval for systems above 16 A per phase must be sought before installation and commissioning. The application form requires technical information including the type of generation equipment, the protection settings, and key electrical parameters for the system. Alongside the ENA G99 application form, an electrical schematic must also be submitted. Any missing or incorrect information could lead to delays in the application process or even a rejection of the application. Once the network has done their required studies, they may need to apply some constraints to the system or request that network upgrades are needed prior to installation and commissioning for a safe connection – this can increase both the project cost and timescales.
- Structural Survey: Before installation, the roof needs to be signed off by a qualified structural engineer or competent person to state that the roof structure is suitable to take the additional loading of the solar panels. If the roof is deemed to not be structurally sound, then often this can be a blocker as structural upgrades are very expensive. However, there are lighter weight options for roof mounted solar panels that can be explored as a much more cost-effective solution compared to structural upgrades.
- Planning Permission: Roof mounted solar panels don’t typically require an extensive planning process, provided they are designed within the permitted development rights. Assuming the design meets permitted development, then only prior approval will be required for systems above 50 kWp, and any systems rated below 50 kW won’t need any engagement with the local planning authority.
Whilst this might seem like a lot to tick off as part of the pre-installation compliance, it is very important, and a good installation company should be able to do all of this on the client’s behalf. The good news is that all the above can run concurrently and will typically only take 2-3 months to be completed.
Are there funding options available?
Solar can be seen as an investment with a hefty price tag and only an option for businesses who are ‘cash rich’; however, with many different funding routes available this isn’t the case. Power Purchase Agreements (PPAs) are often the most popularised funding solution for solar. They are a long-term arrangement (often 20 years), whereby the client pays for the energy produced by the system at a much-reduced rate vs the grid electricity import. This provides long term energy security by locking in an agreed volume of energy (solar generation) at a rate below the market rate. As PPAs require no upfront capital investment and the savings are greater than the repayments, this provides a business with immediate operational savings that can be reinvested into other areas of the business. Alternative funding options include Hire Purchase (HP) or Energy as a Service (EaaS), which are typically shorter-term arrangements, often 7-10 years.
How quickly can ROI be generated?
If deciding not to go down the funding route and opting for a capital investment then a well-designed roof mounted solar PV system will typically have a payback period of around 5 years, or sometimes even lower. This is even after factoring in the operation and maintenance costs, which should include an annual electrical servicing and inspection, as well as annual or biennial module cleaning depending on the location. Understanding the maintenance requirements and ensuring that they have been considered within the design can help to further improve the ROI, even if the capital cost increases. For example, installing permanent fall protection and roof access alongside the solar array will reduce the operational spend as it mitigates the needs for temporary protection during the O&M phase.
