We’re proud to announce that as part of our local weather info that is presented here on the Verde Solar Power webpage, we are now including an index of solar gain for our local area of Arizona. This Solar Gain Index is a daily prediction of how productive a typical solar electric system will be for the date as a percentage of what its maximum capability is. Clear days in late April will often produce close to 100% of a solar array’s potential, while days at the end of December will be more like 73%. The typical array this is figured for is facing due South at a 20 degree tilt. Besides the inherent solar gain variations due to the movement of the sun as it changes through the year, the main factor determining solar gain is the weather of course, and we base our predictions on local data from accuweather.com. Our prediction accuracy has been about 90% – Arizona is pretty easy to do predictions because it is so consistently sunny here.
Please use this Solar Gain Index to keep a check on your own solar system and to verify that it is working up to its potential. Most solar inverters display data of daily and cumulative production and by noting this each evening, you can compare what your system has produced relative to the Solar Gain Index. On a clear day, next April, collect a reading of what your system has produced for the day and keep this as a baseline reference of a 100% day. Then all year round, you will be able to use this Solar Gain Index to see how your solar system is performing.
You will notice that in late spring when the sun is aligned straight to your PV array and the temperatures are still cool, your solar system will be the most productive of the year. Later, in the summer, the sun is more straight overhead and not so well aligned with your panels – plus is running very hot which makes PV panels less efficient. Then in the fall, the gain improves again as the alignment improves – but production is just not as good as the spring. Finally, Winter months are the worst with short days, the sun being low in the sky, and typically more cloudy weather.
Keep an eye on your Solar Gain!