Marion Cundari, Portfolio Analytics Manager
A PPA is a long-term financial commitment worth many millions of dollars. As an energy buyer, it’s important to have an accurate revenue value each month for reporting; and for a developer, accurately accounting for revenue is critical to ensure large-scale projects stay in the black.
REsurety currently manages over 35 GW of Power Purchase Agreements (PPAs). Our 2025 analysis of these managed portfolios revealed average annual invoice errors amounting to $75 per MW per year. If we extrapolate this finding to the estimated total global PPA market –approximately 320 GW, this suggests an annual absolute value of invoicing errors across the industry could be as high as $24 million.
Why are there so many invoicing errors?
In REsurety’s experience, many of the costly mistakes stem from relying on spreadsheets like Excel for complex invoicing and reconciliation. Often, faults such as cell reference errors, shifted time series data, and simple copy/paste failures result in tens of thousands of dollars of invoice errors.
Word to the wise – check your PPA reports extra carefully this month. Daylight Saving Time began on Sunday, March 8th, when we moved our clocks forward an hour in the US. In the coming weeks, we anticipate an increase in time-series errors as March invoices begin arriving with issues related to the handling of this time change.
Furthermore, this manual process often relies on market data that are static downloads rather than live connections to the occasionally revised ISO published market prices; a programmatic approach with live data feeds limits stale data. While a powerful tool for certain tasks, Excel is not designed as a management tool to handle the intricate, multi-sourced data processing required for accurate and compliant invoicing. This manual approach also frequently leads to discrepancies between supporting calculations and the final invoices, creating a lack of auditability and making it difficult to uncover the source of the errors.
Utilize the right tools for the job!
The often overlooked inconsistencies in PPA invoices and supporting files are exactly what CleanSight Manage with Auditing is designed to address. By automating the auditing process and moving away from error-prone manual spreadsheets, you can ensure every invoice is accurate and compliant with your contractual agreements.
Learn more about CleanSight Manage with Auditing. Book a call today:
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