Rooftops, batteries and risk: What you need to know to power the net-zero future

1 September 2025

By Robert Gardner, Renewable Energy & Power Leader – GB Retail at WTW

How rooftop solar and lithium-ion batteries are transforming the UK’s energy landscape and what risks businesses and insurers must prepare for.

The net-zero challenge is a $110 trillion opportunity

According to the Energy Transitions Commission, $110 trillion1 is the capital investment needed over the next 25 years to transform our energy systems, economies, and societies to reach carbon neutrality by 2050.

In the UK, this involves rapidly scaling technologies such as rooftop solar photovoltaic (PV) systems and battery energy storage systems (BESS), introducing new and evolving risks that you must understand and manage effectively.

Rooftop solar: Big potential, big responsibilities and new risks

The rapid growth of rooftop solar installations, particularly on warehouses, commercial buildings and industrial facilities, presents both opportunities and challenges. The features that make rooftop solar attractive can also complicate insurance coverage and operational reliability. When it comes to rooftop photovoltaic (PV) systems, you should be aware of:

• Third-party ownership complexities: The contractual landscape can be complex, with multiple parties involved, including the roof owner, building occupier, solar equipment owner and maintenance provider. Understanding these relationships is crucial, as they can raise potential liability issues if not properly managed

• Fire and water ingress risks: These are among the most common insurance claims related to rooftop solar installations. Claims often result from poor installation practices or the use of combustible insulation materials

• Access and maintenance challenges: Routine maintenance is essential for rooftop solar systems, but ensuring that all parties have proper access can be a challenge

• Structural integrity: You must assess whether the roof is load-bearing and consider factors such as snow and wind loads to ensure the structural integrity of the building.

By understanding these risks and taking steps to mitigate them, you can better manage the complexities associated with rooftop solar.

Mitigating thermal runaway risks in Battery Energy Storage Systems (BESS)

Lithium-ion batteries play a crucial role in solar infrastructure by storing energy for use during periods of low generation or high demand. However, insurers remain concerned about the risk of thermal runaway, a chemical reaction that can lead to a self-sustaining increase in temperature. Recent significant battery fires in California have intensified insurer scrutiny of this issue.

To manage the risks associated with BESS, you can implement several key measures:

• Maintain a 25-foot spacing between battery units to reduce the risk of fire spread

• Install blast walls, passive venting systems and clean-agent suppression systems to mitigate the effects of a thermal runaway event

• Conduct UL9540A testing at the cell, module and system levels to ensure the safety and reliability of the BESS

• Ensure access to a reliable water supply and maintain trained response teams to handle emergencies effectively

• Prepare detailed engineering reports and documentation on battery chemistry to demonstrate a thorough understanding of the system’s risks and mitigation strategies.

Insurers will expect to see these or similar measures implemented, or a compelling justification for alternative approaches.

Emerging risks in smaller lithium-ion battery applications

Lithium-ion battery risks aren’t limited to utility-scale BESS. They’re also emerging in:

· E-bikes and e-scooters

· Warehouse robots and Automated Guided Vehicles (AGVs)

· Electric agricultural and construction equipment

The increasing prevalence of these technologies has led to a rise in lithium-ion battery-related incidents. For instance, in 2023, the London Fire Brigade responded to 104 e-bike and 19 e-scooter fires2, and there was a significant increase in lithium battery fires across the UK.

Refining your risk management approach

As the energy landscape continues to evolve, staying informed and adaptable will be key to navigating the challenges and opportunities that lie ahead. You should regularly review and update your risk management strategies to ensure they remain effective and relevant. By doing so, you can capitalise on the opportunities presented by rooftop solar and BESS while minimising their risks.

To secure favourable insurance terms, consider the following key strategies:

· Bring your insurance broker into the project planning stage early to ensure a smooth insurance process.

· Develop a comprehensive underwriting submission with technical details to demonstrate a thorough understanding of the project’s risks.

· Create competition among insurers by seeking multiple quotes to secure the best possible terms.

· Document your project’s excellence to differentiate it from others and demonstrate its value to insurers.

To discuss how you can manage and mitigate the risks associated with rooftop solar and BESS, get in touch with our specialists.

Author: Rob Gardner

This is WTW: WTW is an international insurance broker and advisory firm operating in over 140 territories. We work with organisations of all sizes to manage risk, optimise benefits, and support strategic growth through expert advice and tailored solutions. Our Power, Utilities & Renewable Energy group specialise in advising solar businesses.