Why Most Solar Portfolios Underperform (And How To Fix It)

Over the past decade of supporting organizations with managing solar portfolios, we’ve seen a consistent pattern:

Teams invest in solar expecting predictable savings; but over time, utility bills creep back up, and confidence in those investments begins to erode.

The challenge? Solar performance isn’t always easy to see or measure. Without clear financial analytics and active oversight, underperformance can go undetected for months or even years. And when we walk sites with clients or audit their portfolios, we often uncover significant issues: offline equipment, missed utility credits, and unclaimed performance guarantees worth hundreds of thousands of dollars.

In this article, we’ll highlight some of the common reasons solar portfolios underperform, and what you can do to address them.

1. Hidden Downtime

Solar is often a “silent failure” system.

When a chiller or HVAC unit fails, you know immediately. When a solar system underperforms, or goes offline entirely, it can go unnoticed. The only signal is often a higher utility bill, which is easily attributed to rising energy costs.

In reality, underperforming solar can quietly drive significant increases in operating expenses.

What to do:

•    Ensure monitoring systems are fully operational and properly configured
•    Assign clear ownership for monitoring and issue response
•    Implement regular performance reviews (monthly or quarterly)
•    Compare actual production to weather-adjusted expected performance

The goal is simple: detect and resolve issues early before they materially impact your savings.

2. Soiling 

Soiling is one of the most common and overlooked drivers of underperformance. Depending on your location, dirty panels can reduce output by 10% to 30%. And the timing of these losses matters. Soiling losses peak in the summer. And summer production is both highest in volume (more sunlight hours in the day) and highest in value (generation is being valued at peak summer utility rates). That means a 20% loss in July is far more expensive than a 20% loss in January.

What to do:

•    Establish a regular panel washing schedule (typically 1–2 times per year)
•    Adjust frequency based on site-specific conditions 

In most cases, panel washing delivers a rapid ROI and not doing it almost always means leaving money on the table.

3. Lack of Financial Transparency & Accountability

This is often the biggest hidden opportunity. We’ve seen so many versions of this: utility billing errors where clients were owed credits for years, performance guarantees that went unenforced, and contracts that no one was actively managing. We recently audited a performance guarantee for a relatively small portfolio, and found that, per the terms of the agreement, and based on the performance from the solar facilities, the solar company owed their customer $100,000.

The reality is that solar portfolios sit at the intersection of technical performance data, dense solar company & utility agreements, and complex utility tariffs. Without active management, it’s easy for value to slip through the cracks.

What to do:

•    Regularly audit utility bills and credit allocations
•    Track contractual performance guarantees
•    Implement financial reporting that ties production → savings → actual outcomes
•    Assign accountability (internally or via a third-party asset manager)

If your portfolio is expected to generate millions in annual savings, it’s worth ensuring that performance is being actively validated and protected.

Bringing It All Together

A high-performing solar portfolio doesn’t happen by accident. It requires visibility, discipline, and accountability. At Transform Energy Asset Management, this is exactly what we provide. We help organizations bring clarity to a complex and often opaque energy landscape—so they can maximize savings, reduce risk, and get the full value from their infrastructure.

Curious How Your Portfolio Is Performing?

If you’re unsure whether your systems are operating at their full potential or suspect there may be hidden issues, we’d be happy to take a look. Reach out at david.burdick@transformenergy.com to schedule a portfolio review and identify opportunities to improve performance.