Independent commercial solar performance audit
One-off on-site inspection and performance assessment for commercial solar PV and battery storage. Due diligence before acquisition, a second opinion on system performance, or an independent report for insurance, compliance, or a performance dispute. No contract required — the audit stands on its own.
Independent audit
No contract required · standalone report
No obligation · no ongoing commitment
When you need an independent audit
An independent audit gives you an objective picture of a commercial solar system — without the bias of the company that installed it or the provider that maintains it. The report is written for third-party use and designed to support real decisions.
Acquisition due diligence
You are purchasing or leasing a commercial property with an existing solar installation. You need to know what condition it is in, whether it is generating to specification, and what maintenance liabilities you are inheriting. The audit report feeds directly into your due diligence pack.
Insurance compliance
Your insurer requires evidence that the solar installation is in safe working order and professionally maintained. An independent audit provides the documented proof — covering electrical safety, component condition, and compliance with current regulations — from a provider with no conflict of interest.
Performance dispute
Generation figures do not match projections, and your current provider cannot explain why — or you do not trust their explanation. An independent audit benchmarks actual output against expected yield, identifies the cause of underperformance, and provides evidence you can use to hold the responsible party accountable.
Second opinion
Your current O&M provider has recommended significant work — inverter replacement, re-stringing, battery upgrades — and you want an independent view before committing. Our audit assesses whether the recommended work is necessary, proportionate, and correctly scoped.
Landlord or tenant requirement
The lease requires periodic independent assessment of the solar installation, or the landlord needs confirmation that the tenant is maintaining the system to an acceptable standard. The audit report provides the evidence both parties need — written by an independent third party.
Pre-warranty expiry check
Manufacturer warranties on inverters or panels are approaching expiry. An independent audit identifies any faults or degradation that should be claimed under warranty before the window closes — documented with the evidence needed to support the claim.
What the independent commercial solar audit covers
Every audit follows the same thorough methodology, whether the system is a 20 kW rooftop array or a multi-hundred kW commercial installation. The scope is comprehensive by default — we do not offer a reduced inspection. Available UK-wide.
Inverter inspection
Visual and electrical inspection of all inverters — error code history, firmware version, fan condition, heat damage assessment, and performance benchmarking against manufacturer specifications. All major commercial brands including SMA, Huawei, Solis, SolarEdge, GoodWe, Fronius, and others.
Panel and string testing
String-level voltage and current measurements to identify failed panels, bypass diode faults, or wiring issues. Visual inspection for hotspots, microcracks, snail trails, delamination, and physical damage. Shading assessment and soiling evaluation where relevant.
Electrical safety and compliance
DC isolator condition, cable routing and integrity, earth continuity, insulation resistance testing, and verification of protective device settings. DNO connection agreement reviewed for G98/G99 compliance. Any safety issues flagged for immediate attention with a clear risk assessment.
Battery storage assessment
Where battery storage is present — state of health, charge/discharge cycle history, BMS configuration, cell balancing status, and thermal management assessment. Warranty status verified where manufacturer records are available. Degradation benchmarked against expected lifecycle.
Yield benchmarking
Actual generation compared against expected output based on system size, orientation, tilt, location, and shading profile. Where monitoring data is available, we analyse historical trends to identify degradation patterns, seasonal anomalies, and periods of underperformance. If monitoring is offline, we note this and recommend restoration.
Written report
A comprehensive written report documenting system condition, all findings, identified faults, performance benchmarks, safety compliance status, and clear recommendations. The report is designed for third-party use — share it with your landlord, insurer, legal team, or procurement department. Delivered within five to ten working days of the site visit.
Why independence matters
Most commercial solar maintenance providers are also installers. When the same company that benefits from selling you new hardware is the one advising you on whether your existing equipment needs replacing, there is a structural conflict of interest that undermines the credibility of every recommendation they make.
STS is not tied to any manufacturer, installer, or distribution network. We carry out inverter replacements, component swaps, and hardware repairs — but we have no incentive to recommend work that is not necessary. When we say a component needs replacing, it is because it does.
That independence is why our audit reports carry weight with third parties. If you need an objective assessment of a commercial solar asset — whether for acquisition, insurance, a performance dispute, or simply a second opinion — the report needs to come from a provider with no commercial agenda.
We work with all major inverter and battery brands used in UK commercial installations. Our engineers are experienced with three-phase systems, string and micro-inverter configurations, large-scale battery arrays, and the monitoring platforms that connect them. Read more about how we work.
Independent audit — frequently asked questions
The audit is a comprehensive on-site inspection covering all inverters, panels, cabling, isolators, battery storage (where present), mounting systems, and electrical connections. We test string-level performance, verify monitoring accuracy, benchmark actual yield against expected output, and check safety compliance. The result is a written report documenting current system condition, any faults or underperformance, and clear recommendations.
The scope of the on-site work is similar — the same thorough inspection is carried out. The difference is context and purpose. An annual inspection is part of an ongoing O&M contract and feeds into a continuous maintenance record. An independent audit is a standalone assessment, often commissioned for a specific reason — due diligence, a second opinion, compliance, or a performance dispute. The audit report is designed to stand on its own and be shared with third parties.
Yes. The audit report is written to be shared with insurers, landlords, facilities managers, and procurement teams. Because STS is independent — not tied to any manufacturer or installer network — the findings carry credibility as an objective assessment. We can tailor the report format to meet specific compliance requirements if needed.
No. The independent audit is a standalone service with no obligation to proceed to an O&M contract. Many clients use the audit report independently — for due diligence, to challenge a previous provider, or to support an insurance claim. If you do want to move to ongoing maintenance, the audit serves as the baseline for an O&M contract, but that decision is entirely yours.
The on-site inspection is typically completed in a single visit — half a day for most standard commercial rooftop systems, a full day for larger or more complex installations. The written report is delivered within five to ten working days, depending on the scope and any additional data analysis required.
Yes. We audit commercial solar systems regardless of who installed them. We are not tied to any installer network or manufacturer — our assessment is based solely on the condition and performance of the equipment on site. If the original installer is no longer trading or you have concerns about their work, an independent audit provides the objective evidence you need.
Related commercial services
Annual O&M contracts
Scheduled inspections, real-time monitoring, performance reporting, and priority emergency response. £795/year.
EmergencyEmergency repair
Same-day remote triage, next-business-day on-site for contract holders. Inverter replacement, fault diagnosis, and safety isolation.
TakeoverSystem takeover
Transition maintenance from a previous provider. Baseline audit, documentation recovery, and structured handover into ongoing O&M.
Request an independent audit
Tell us about the system and the reason for the audit. We will confirm scope and pricing — usually within one business day. No obligation to proceed to ongoing maintenance.