The Case: £26,000 Lost to an Underperforming System

Our client had invested in a combined solar PV and battery system that promised strong financial returns. But within the first year, the system was underperforming so badly that projected savings were nowhere to be seen. Instead of cutting energy bills, the project had left the business £26,000 out of pocket.

We were brought in as Independent Solar Consultants to act as expert witnesses. Our role was clear: review the system design, installation, and performance, and provide independent technical evidence to support a financial recovery claim.

What we uncovered was a “perfect storm” of solar project pitfalls — inaccurate performance modelling, incompatible equipment, and critical structural oversights. Sadly, all of these could have been avoided with independent due diligence before the project began.

Lesson 1: Performance Calculations Must Be Verified

The installer’s performance estimates were not just optimistic — they were factually incorrect. The system was modelled as if the panels faced due south (the optimal orientation in the UK for maximum solar yield). In reality, the panels were facing a completely different direction, leading to far lower energy generation.^[1]

Orientation and tilt angles make a significant difference. According to the European Commission’s Joint Research Centre (JRC), incorrect orientation alone can reduce annual yield by 15–25% in the UK.^[2]

A quick early-stage review using professional modelling tools such as PVSyst would have flagged this error immediately. Independent consultants routinely validate installer projections with bankable datasets like PVGIS and Meteonorm, ensuring businesses have realistic expectations before signing contracts.^[3]

Key takeaway: Never accept performance figures at face value. Always have independent verification of the Specific Annual Yield before committing to investment.

Lesson 2: Equipment Compatibility Matters

In this case, the batteries and inverters were not designed to work together. Instead of charging efficiently, the batteries were sometimes charging during peak-rate hours — the most expensive time to draw electricity. The result? Instead of reducing bills, the system was actively increasing costs.

Equipment compatibility is one of the most overlooked aspects of solar design. A BloombergNEF report shows that mismatched systems are a leading cause of performance underachievement, accounting for up to 20% of post-installation issues in commercial PV.^[4]

Independent consultants check not only technical compatibility but also warranty alignment. If a battery is paired with an unsupported inverter, manufacturers may refuse warranty claims — leaving the client exposed to future replacement costs.^[5]

Key takeaway: Compatibility isn’t just technical — it’s financial. Independent design reviews ensure technology choices support long-term ROI, not just short-term installer margins.

Lesson 3: Structural and Design Oversights Can Be Costly

Perhaps the most alarming discovery was that no structural calculations had been performed on the building. The roof was carrying additional loads without verification of its integrity — a major risk for both safety and insurance compliance.

UK building regulations require solar installations to be assessed for load-bearing capacity, wind uplift, and weatherproofing.^[6] Skipping this step not only jeopardises safety but can void both roofing warranties and insurance policies.

As independent consultants, one of our first steps is to commission structural assessments and electrical safety checks. This ensures that solar projects are both technically sound and legally compliant.^[7]

Key takeaway: Without proper design oversight, solar projects risk being unsafe, non-compliant, and uninsured — with costly consequences.

Why Engage Independent Solar Consultants Early

This case highlights why independent consultancy isn’t a “nice-to-have” — it’s a safeguard. For a fraction of total project costs, businesses gain a trusted advocate whose sole role is to protect their interests.

We help clients by:

• Validating performance models with independent tools like PVSyst and PVGIS.
• Assessing technology compatibility across inverters, batteries, and monitoring systems.
• Ensuring structural and compliance checks are carried out before installation.
• Holding installers accountable during procurement, construction, and commissioning.

Businesses that engage consultants early avoid the risk of expensive disputes and protect their investments against common pitfalls.

Expanding the Lessons: What Businesses Can Learn

This case may sound extreme, but it’s far from unique. Across the UK and Europe, underperforming solar projects have been reported in multiple sectors — from retail and warehousing to food processing and manufacturing.^[8] Each time, the root causes are strikingly similar: inflated projections, poor equipment matching, or missing compliance checks.

The good news? These problems are preventable. Independent solar consultants bring a systematic process to design reviews, financial modelling, and risk management that reduces the chances of expensive errors slipping through.

Compliance and Risk Management

Solar projects in the UK must comply with a complex set of rules, including G99/G100 grid connection standards, BS 7671 wiring regulations, and health and safety legislation.^[9] Missing compliance can result in projects failing commissioning or even being disconnected from the grid.

Globally, compliance requirements vary. In Europe, IEC standards govern module safety and inverter performance, while in markets like the U.S. the National Electrical Code (NEC) sets stringent safety requirements.^[10] Independent consultants familiar with these frameworks can ensure multinational businesses apply consistent standards across borders.

Lesson: Compliance isn’t just paperwork — it’s essential risk protection.

The Role of Independent Oversight in Financial Returns

One of the biggest risks in solar is overpromised ROI. Industry research shows that financial underperformance is a leading driver of disputes between clients and EPC contractors.^[11] Independent ROI modelling provides a reality check, incorporating sensitivity analysis on energy prices, system degradation, and consumption patterns.

For example, the Carbon Trust highlights that energy price volatility can swing commercial project paybacks by several years depending on contract structures.^[12] Independent assessments help boards prepare for multiple scenarios rather than relying on “best case” sales numbers.

Lesson: Independent modelling protects businesses from wishful thinking and ensures solar projects stand up to board-level scrutiny.

Digital Monitoring and Long-Term Value

Independent consultants don’t just add value at the start of a project. Ongoing oversight through digital monitoring and performance audits ensures systems continue to perform as promised. By integrating SCADA systems or cloud-based portals, consultants provide transparent performance data to benchmark actual yield against projections.^[13]

With tools like digital twins, performance can be compared against modelled expectations, helping detect early signs of degradation or operational inefficiencies. This reduces downtime and preserves financial returns over the long term.

Global Lessons from Independent Solar Oversight

The lessons from this UK case apply globally. In Australia, businesses have faced similar losses due to poorly designed commercial solar systems that failed to deliver expected bill reductions.^[14] In emerging markets across Africa and Asia, international development banks now routinely require independent technical advisors before funding is released.^[15]

These global practices demonstrate that independent oversight isn’t an “optional extra” — it’s a recognised safeguard for investors and operators worldwide.

Making Independent Consultancy Part of Your Strategy

Businesses investing in solar should view independent consultancy as part of their risk management strategy. Just as legal counsel protects contracts and auditors protect finances, independent solar consultants protect energy investments.

Engaging consultants early delivers several strategic benefits:

• Prevents costly mistakes before contracts are signed.
• Improves bankability for projects seeking financing.
• Increases confidence for boards and investors.
• Strengthens compliance with regulatory and insurance requirements.
• Supports long-term performance through monitoring and audits.

Conclusion: Don’t Wait Until It’s Too Late

Our client’s story — losing £26,000 to an underperforming system — is a cautionary tale. The dispute, the frustration, and the wasted time could all have been avoided with early independent oversight.

Whether you’re planning your first commercial solar project or scaling up across multiple sites, engaging an independent solar consultant is a safeguard against unnecessary losses. It ensures your investment is safe, compliant, and delivering the savings and sustainability outcomes you expect.

Don’t wait until you’re counting losses to call us in. Engage independent expertise from the start — and protect both your bottom line and your sanity.

References

1. Solar Energy UK — Orientation and Tilt Guidance: link
2. European Commission JRC — PVGIS Documentation: link
3. PVSyst — Solar Simulation Software: link
4. BloombergNEF — PV Module & Storage Integration: link
5. Clean Energy Council — Battery Warranty Guidelines: link
6. UK Government — Building Regulations for Solar: link
7. Institution of Structural Engineers — Rooftop Solar Guidance: link
8. Carbon Trust — Commercial Solar Reports: link
9. IET — Wiring Regulations (BS 7671): link
10. IEC — PV Module and Inverter Standards: link
11. IRENA — Quality Assurance in Solar PV: link
12. Carbon Trust — Energy Price Risk & Forecasting: link
13. IEA PVPS — PV System Monitoring Best Practices: link
14. Australian Energy Regulator — Commercial PV Case Studies: link
15. World Bank — Scaling Solar Program: link