About Solar PV Yield Calculator
The solar PV yield calculator estimates the annual and monthly energy output of a photovoltaic array from its peak capacity, location irradiance, tilt, azimuth, and system losses per IEC 61853, SAP Appendix M, and PVGIS methodology. It is used by solar designers to size arrays and forecast generation, savings, and payback.
Choose a panel type and quantity, set the tilt and azimuth, pick a location, and adjust shading and system losses. The tool returns the peak capacity, the annual yield, the specific yield, the performance ratio and capacity factor, plus monthly generation, savings, CO2 avoided, and payback, all updating in real time.
How It Works
- Compute the peak DC capacity as panel watt-peak times the number of panels, and the array area as panel area times the count.
- Derive a tilt and azimuth correction factor from the array orientation relative to the site latitude and the optimal azimuth.
- For each month, multiply the plane-of-array irradiance by the peak capacity, the tilt factor, and (1 - shading)(1 - system losses)(1 - temperature loss).
- Sum the monthly yields for the annual yield, then derive specific yield, performance ratio, capacity factor, savings, CO2 avoided, and payback.
Worked Example
Twenty 400 Wp panels (1.95 m2 each) give a peak capacity of (400 * 20) / 1000 = 8 kWp and an array area of 1.95 * 20 = 39 m2. In Madrid (1800 kWh/m2/year, latitude 40.4 deg, south-facing, 35 deg tilt) with 5% shading and 14% system losses, the annual yield is about 9400 kWh, a specific yield near 1175 kWh/kWp.
Formulas
- Peak capacity
Pkwp = (Wp * N) / 1000- Monthly yield
E = H * Pkwp * tiltFactor * (1 - shading) * (1 - losses) * (1 - tempLoss)- Specific yield
specificYield = annualYield / Pkwp- Capacity factor
CF = (annualYield / (Pkwp * 8760)) * 100- Temperature loss
tempLoss = abs(tempCoeff) * max(0, Tavg - 25) / 100
Standards & References
- IEC 61853
- SAP Appendix M
- PVGIS
Frequently Asked Questions
How is annual yield estimated?
Each month the plane-of-array irradiance is multiplied by the peak capacity, the tilt and azimuth factor, and the loss terms (1 - shading)(1 - system losses)(1 - temperature loss). The twelve monthly yields are summed for the annual figure.
What is specific yield?
Specific yield is the annual energy per kilowatt of installed peak capacity (kWh/kWp). It normalises output so arrays of different sizes can be compared, and typically falls between about 800 and 2000 kWh/kWp depending on the site.
How do tilt and azimuth affect output?
The tool derives a correction factor from the array tilt relative to the site latitude and from the azimuth relative to the optimal direction (south in the northern hemisphere). Orienting toward the optimal tilt and azimuth maximises the factor toward 1.0.
What is the performance ratio?
The performance ratio compares the actual yield to the ideal yield (irradiance times array area times module efficiency). It captures all real-world losses and usually lands between roughly 0.7 and 0.85 for a well-designed system.