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Cleaning Requirements for Solar Projects Under Performance-Based Contracts

Performance-based agreements are increasingly shaping how large-scale solar projects are financed, operated, and maintained. Under these contracts, system owners and operators are held accountable for delivering a defined level of energy production or system availability. That means every factor that affects output—including soiling—becomes a performance risk that must be actively managed.

For companies like Green Facility Cleaning, this creates a focused role in supporting asset performance through targeted cleaning services. In this structure, cleaning becomes one of the most practical tools for restoring lost output and helping maintain contractual performance expectations.

Green Facility Cleaning does not monitor system production data and operates strictly based on customer service requests and site scheduling.

Understanding Performance-Based Solar Contracts

Performance-based solar contracts tie financial outcomes to system performance metrics such as energy production or availability. These agreements are commonly used in power purchase agreements (PPAs) and long-term O&M arrangements. Instead of being paid solely for installation or maintenance, service providers and asset owners are held accountable for sustained system output over time.

If production falls below expected levels, financial penalties or revenue adjustments may apply depending on contract terms. This makes identifying and addressing performance losses critical.

One of the most common and predictable contributors to energy loss is soiling. Dust, pollution, pollen, and other environmental contaminants can reduce panel efficiency by a few percent in mild conditions and significantly more in arid or high-dust regions.

Green Facility Cleaning focuses on providing professional cleaning services that help restore panel performance when soiling becomes a limiting factor. The company does not monitor system production data; instead, customers or their monitoring providers identify performance issues and request service accordingly.

Key Points

  • Performance-based contracts tie revenue to system output or availability
  • Soiling is a predictable and manageable source of performance loss
  • Financial penalties may apply when output falls below contract thresholds
  • Green Facility Cleaning provides responsive cleaning services based on customer requests

Sources:

  • National Renewable Energy Laboratory (NREL) – Best Practices for Operation and Maintenance of Photovoltaic Systems
    https://www.nrel.gov/docs/fy19osti/73822.pdf
  • International Energy Agency (IEA PVPS) – Operation and Maintenance of PV Systems
    https://iea-pvps.org/key-topics/operation-maintenance/

The Impact of Soiling on Energy Production

Soiling reduces the amount of sunlight reaching photovoltaic cells, directly lowering energy output. The rate of accumulation depends on environmental conditions such as dust levels, rainfall patterns, agricultural activity, and nearby construction.

In dry and desert environments, soiling losses can accumulate quickly. Even in regions with periodic rainfall, dust and debris can persist long enough between natural cleaning events to impact production.

Below is an illustrative example of how output may decline over time without cleaning:

Energy Output (% of Expected Production)

100 |●
 98 |    ●
 96 |       ●
 94 |          ●
 92 |              ●
 90 |                   ●
 88 |                        ●
     ————————-
       Wk1  Wk2  Wk3  Wk4  Wk5

This gradual decline reflects how soiling typically accumulates under real-world conditions. In performance-based contracts, even small percentage losses can become financially significant over time.

Key Points

  • Soiling reduces solar panel efficiency by blocking sunlight
  • Loss rates vary depending on environment and weather patterns
  • Performance declines gradually but can become financially material
  • Cleaning restores output by removing surface contamination

Sources:

Cleaning as a Tool for Uptime and Performance Restoration

Uptime in solar systems refers to the amount of time a system is operational and producing energy as expected. In performance-based contracts, uptime often extends beyond simple system availability and includes whether the system meets expected output levels.

It is important to distinguish between two concepts:

  • Operational uptime: the system is powered and functioning
  • Performance uptime: the system is producing at expected levels

Soiling can reduce performance uptime even when equipment is fully operational.

Green Facility Cleaning provides cleaning services that help restore performance when customers or their monitoring systems identify a drop in energy output.

Key Points

  • Uptime includes both system availability and performance output
  • Dirty panels can reduce effective performance uptime
  • Green Facility Cleaning responds to customer-identified performance issues
  • Cleaning helps restore energy output without system repairs

Sources:

  • IEA PVPS Task 13 – Performance Assessment of PV Systems
    https://iea-pvps.org/wp-content/uploads/2020/01/IEA-PVPS_T13-11_2018_Performance_Assessment.pdf
  • NREL – PV System Performance Monitoring Overview
    https://www.nrel.gov/docs/fy14osti/60120.pdf

Determining Cleaning Frequency in Performance-Based Contracts

There is no universal cleaning schedule for solar assets. Cleaning frequency depends on environmental conditions, system design, and contractual performance requirements.

Key influencing factors include:

  • Local dust and pollution levels
  • Seasonal weather patterns
  • Panel tilt and installation type
  • Contractual performance thresholds

In many cases, customers determine cleaning needs based on their internal performance monitoring systems. When output declines and natural recovery (such as rainfall) is insufficient, cleaning is scheduled to restore performance.

Green Facility Cleaning supports this process by providing on-site cleaning services based on customer requests and operational requirements. Site evaluations and customer-provided operational history help guide practical scheduling recommendations.

Key Points

  • Cleaning frequency varies by environment and system design
  • Customers or their providers typically identify when cleaning is needed
  • Over-cleaning increases cost without added benefit
  • Under-cleaning risks performance losses and contract impacts

Sources:

Risk Mitigation and Financial Implications

In performance-based solar contracts, even small reductions in energy output can have financial consequences. Soiling-related losses, if left unaddressed, can accumulate into measurable revenue impacts over time.

Cleaning is often a cost-effective method of restoring lost production compared to the value of energy regained. However, the decision to clean is typically based on customer monitoring data and operational thresholds rather than continuous third-party oversight.

Key Points

  • Soiling can create measurable revenue losses over time
  • Cleaning is often cost-effective compared to lost production
  • Decisions are typically driven by customer monitoring data
  • Green Facility Cleaning provides service-based cost-benefit support

Sources:

Integrating Cleaning into O&M Strategies

Cleaning is most effective when integrated into broader operational planning. In performance-based environments, cleaning typically works alongside monitoring systems, preventative maintenance, and seasonal planning.

However, Green Facility Cleaning does not monitor system production or performance data. Instead, the company operates as a service provider that responds when customers identify a need for cleaning based on their own monitoring systems or operational assessments.

Coordination with site teams helps ensure cleaning is performed efficiently and with minimal disruption to operations. This responsive approach allows cleaning to support overall system performance without requiring direct involvement in performance tracking.

Key Points

  • Cleaning works alongside broader O&M planning strategies
  • Monitoring and performance tracking are handled by the customer or third parties
  • Green Facility Cleaning operates on a responsive service model
  • Coordination helps minimize operational disruption during cleaning

Sources:

Conclusion: Cleaning as a Performance Restoration Strategy

In performance-based solar contracts, maintaining expected energy output is essential for meeting contractual obligations and protecting revenue. Soiling is one of the most common and manageable causes of performance loss, and cleaning plays a direct role in restoring system output.

Green Facility Cleaning provides responsive cleaning services that support asset performance when customers identify a need. While the company does not monitor system production, it plays an important role in helping operators address soiling-related losses efficiently and effectively.

As solar portfolios continue to expand and performance expectations become more defined, cleaning will remain a key operational tool for maintaining output stability.

Get in Touch

To learn more about how Green Facility Cleaning can support your solar operations, visit greenfacilitycleaning.com, call 951-675-8181, or email service@greenfacilitycleaning.com.