Daily Output Comparison Between Nov/Dec and Jan/Feb

Summary

Outlines the difference in estimated average daily energy output between November/December and January/February. Despite these two periods appearing similar for solar generation Jan/Feb generally produces 10% more energy.

Seasonal solar output changes by around 8–12% between these periods in lower latitudes such as -35, depending on local weather patterns and shading factors.

Here are a few factors influencing this difference:

1. Sun Angle: In the Southern Hemisphere, January and February bring the sun to its highest position in the sky, creating more direct sunlight and optimal angles for solar capture. By contrast, November and December generally have a lower sun angle, meaning that sunlight hits the panels at a slightly more oblique angle. This difference affects the intensity of the sunlight reaching the panels, with higher angles producing more energy.
2. Day Length: January and February have longer days due to the Southern Hemisphere’s tilt toward the sun, providing extended hours of sunlight. Conversely, as the days shorten in November and December, the period available for energy capture is reduced.
3. Weather Patterns: December often sees increased cloud cover or early-summer weather variability, which can reduce solar irradiance compared to the more stable, sunny conditions in January and February.
4. Atmospheric Clarity: Atmospheric clarity refers to how free the sky is from particles, water vapor, and pollutants that can scatter or absorb sunlight. In the peak of summer, January and February often bring drier air, which reduces atmospheric scattering and allows more sunlight to reach the panels. Humidity and particulate matter are generally lower in these months, making the air clearer. In November and December, higher humidity and transitional weather can cause slightly hazier conditions, which can reduce irradiance even on sunny days.

Overall these effects can contribute to output in November and December being 10% less than Jan or February.

String Inverter Design: In systems without microinverters, solar panels are typically connected in series with a central (string) inverter managing the entire array. The overall output is influenced by the weakest panel in the string, meaning any shading, orientation misalignment, or cloud cover affecting even a single panel can reduce the output of the entire string. This effect becomes more noticeable during months with lower sun angles or increased cloud cover, as individual panel performance may vary more significantly.

Lower Efficiency to Begin With: If a system has lower efficiency, it has less capacity to buffer against additional seasonal reductions. When these factors (like sun angle, cloud cover, or atmospheric haze) lower irradiance, the efficiency loss will be more apparent, compounding the already limited output.

Ultimately due to the non-linear shading losses of string inverted systems they can experience a greater disparity in output between Nov/Dec and Jan/Feb.