Are you wondering how the August 21, 2017 solar eclipse will affect your rooftop solar system? The short answer – it’s going to cost you money. How much? Let’s look at the numbers.

In San Antonio, the moon will partially block the sun for approximately 3 hours, which will cause a dip in system production. Per the NASA website, the eclipse starts at 11:40am and ends at 2:38pm with an obscuration peak of 61% around 1:00pm. Using solar production modeling software, the normal production on a typical August 21 was adjusted for the solar eclipse event. With the production loss (see the graph), we are able to estimate the loss in dollars. For a 8kW system, the eclipse is going to cost you $0.84!

The same size system in Los Angeles (LA) performs similar to the San Antonio (SA) system because the solar irradiance levels of 5-6 kWh/m2/day are similar. Plus, the 2017 solar eclipse obscuration rates of 62.2% in SA is very close to the LA rate of 62%.

Let’s look at the differences. Due to the different times zones, the solar eclipse will occur during the morning hours in LA (9am – 11am) compared to SA which will experience the eclipse during midday (11:30am – 2:30pm). Peak solar production occurs midday so SA loses more production. Not so fast, energy costs are higher in LA. While the lost solar production is less in LA, it has higher value. The higher value energy in LA offsets the lower production loss so systems in SA and LA experience the same financial impact. The PV systems in SA and LA lose $0.84 and $0.85 respectively.