Accurate energy simulation is the cornerstone of project finance in solar energy. A poorly calibrated model can cost millions in lost production or block financing for an otherwise viable project.
Why does simulation accuracy matter?
When a bank or investment fund evaluates a utility-scale solar project, the first thing they examine is the expected production. P50 and P90 estimates determine the Debt Service Coverage Ratio (DSCR) and, therefore, the viability of the financing.
A 5% overestimation in P50 can:
- Push the DSCR below the minimum threshold required by the lender
- Invalidate the cash flow projections in the financial model
- Delay financial close by months or even years
The three pillars of a bankable simulation
1. Quality solar resource data
The foundation of any simulation is the irradiation time series. Not all meteorological data is equal:
- ERA5 (ECMWF): high-resolution global reanalysis, the international reference
- MERRA-2 (NASA): a robust alternative, especially for projects in the Americas
- Satellite + on-site measurement: optimal combination when a meteorological station exists at the site
The minimum acceptable for a bankable project is a series of at least 10 years, with bias correction when combining satellite data with ground measurements.
2. Validated loss modeling
System losses represent the difference between incident energy and energy delivered to the grid. The most common errors affect:
- Near shading: inaccurate horizon calculation algorithms
- Module temperature: NOCT models vs. actual manufacturer temperature coefficients
- Soiling: underestimated dust losses, especially in arid climates
- Inverter losses: part-load efficiency not correctly modeled
3. Monte Carlo uncertainty analysis
P90 is not simply calculated by applying a conservative margin to P50. A rigorous analysis requires:
- Identifying all sources of uncertainty (solar resource, losses, degradation)
- Assigning probability distributions to each source
- Running thousands of Monte Carlo iterations
- Extracting the P50, P75, P90, and P99 percentiles from the resulting distribution
This is the approach accepted by international banks and infrastructure funds.
Conclusion
A bankable simulation is not just a number: it is a technical document that withstands scrutiny from independent engineers, banks, and insurers. At Heliosolve, we apply these criteria to every project we analyze.
Do you have questions about the quality of your project’s simulation? Contact us for a no-commitment technical review.