How Solar Benchmark Calculates Your Expected Production
We don't guess. We model your specific system using real weather data and peer-reviewed physics — accurate to within 5–7%.
The Problem
Why Averages Don't Work
Every solar monitoring app shows you what your system produced. The hard part is knowing what it should have produced.
Most tools — including the widely-used PVWatts calculator — estimate expected production using a “Typical Meteorological Year”: a synthetic average built from 15–30 years of weather records. But no actual month matches the average month. If January had 30% more cloud cover than typical, a TMY estimate will overstate expected production by 30% or more.
January: TMY Estimate vs. Actual
TMY Estimate
Actual
740 kWh
520 kWh
Is this a real problem or just a cloudy month?
TMY can't tell you. We can.
Data Sources
Real Weather, Real Panels
We use hourly weather data from ERA5 — the world's most comprehensive atmospheric reanalysis dataset, widely used in climate science and energy modeling. ERA5 is the gold standard for historical weather data.
Your panel specs come from the California Energy Commission's publicly maintained database of over 30,000 photovoltaic modules — giving us manufacturer-specific characteristics for your exact panel model, not generic assumptions.
ERA5 Reanalysis
Hourly irradiance, temperature, and wind speed for your exact location.
CEC Module Database
30,000+ PV modules with manufacturer-specific electrical and thermal characteristics.
The Physics
Six Steps from Sunlight to Verdict
Each hour of the month runs through our physics pipeline. Here's what happens at each stage.
Solar Position
For every hour of the month, we calculate the sun's exact position — altitude and azimuth — relative to your location using astronomical algorithms.
Plane-of-Array Irradiance
We convert horizontal irradiance to the light actually hitting your tilted panels using the Perez transposition model — the same model used by PVsyst.
Cell Temperature
Solar panels lose efficiency as they heat up. We model cell temperature using ambient temperature, wind speed, and your module's specific thermal characteristics.
DC Power Output
Using your module's real electrical characteristics — efficiency curve, temperature coefficients, nameplate rating — we calculate expected DC power output for each hour.
System Losses
We apply a calibrated loss chain: inverter efficiency, wiring and mismatch losses, soiling by region and season, and technology-specific degradation rates.
Expected vs. Actual
We sum the hourly expected production into a monthly total and compare it to your actual data. The result is a Performance Ratio — the percentage of expected production your system delivered.
Accuracy
Why This Is More Accurate
Side-by-side: traditional estimates vs. Solar Benchmark.
Your Report
What Your Report Tells You
Each monthly health report gives you a complete picture of your solar system's performance — in plain English, not engineering jargon.
Expected production
for the month, given actual weather at your location
Actual production
from your uploaded monitoring data
Performance Ratio
how your system performed relative to physics-based expectations
Health status
a plain-English verdict on whether your system is performing normally
Trend analysis
month-over-month and seasonal patterns
Recommended actions
when warranted, specific next steps to take
If your system is healthy, we tell you. If something needs attention, we tell you that too — with enough specificity to have a productive conversation with your installer.
Solar Health Report
March 2026
Healthy6-Month Trend
Performance improving — up from 68% in January
Recommended Actions
No action needed — system performing as expected
Spring cleaning: consider panel wash before peak season
Our Standards
Built on Industry-Standard Methods
These are the same methods and data sources used by professional solar engineers, asset managers, and tools like PVsyst. We've made them accessible to homeowners.
pvlib
Sandia National Laboratories
Open-source photovoltaic modeling library maintained by the PV Performance Modeling Collaborative.
Perez 1990 Model
Industry Standard
The standard method for calculating irradiance on tilted surfaces, used by PVsyst and professional tools.
CEC Module Database
California Energy Commission
The most comprehensive publicly maintained database of PV module characteristics.
ERA5 Reanalysis
Global Reanalysis
The world's most comprehensive atmospheric reanalysis dataset, used globally for energy modeling and climate research.
IEC 61724
International Standard
The international standard metric for solar system performance assessment (Performance Ratio).
Independent Analysis
Solar Benchmark
No installer partnerships, no manufacturer relationships. Our only customer is you.
Your system is producing right now.
Do you know if it's performing?
Get an independent, physics-based health report for your solar system.
Free to join. We'll notify you when your report is ready.