• Adam H. Cooke

Solar Panel Angle Difference I

It is a major investment to put in solar. You want to make the most of your investment, whether you are a homeowner or a business looking to invest a few thousand dollars.

The tilting of solar panels can make a huge difference in energy output and financial return.

What is the Deal with Tilt Angle?

It is well-known that solar panels have a tilt effect on their output. How big is the effect? Is it a major economic change or a minor benefit?

We used Aurora Solar software to model a flat roof in Phoenix. To see how much additional energy can be gained each year, we started with flat panels. We then increased the tilt angle to the south. The rule of thumb seems to be that the optimal tilt angle should roughly equal the latitude of the site. We include a result with a tilt of 33.4°, which is the latitude at Phoenix. The graph below shows the results.

Annual energy output vs panel tilt angle, for a South-facing 5 kW array in Phoenix, Arizona

The tilting of the panels can significantly increase energy output. At 30 degrees tilt, the maximum energy output is 14% more than that of flat panels. This is a lot of energy over the 25-year life span of the panels. Titling should be considered for roofs with flat roofs.

If your roof has a pitch of 20 degrees to the south, it will only get you an additional 1.5% by adding 10 degrees to increase its tilt to reach a total of thirty degrees. It is unlikely that the small increase in energy production is worth the additional cost. There is more hardware and more labor required to tilt panels.

The graph shows that while the optimal angle was close to Phoenix's latitude (33.4 degrees), it is not at the exact same angle. The angle of tilt can only be approximated by using the latitude.

How would this change if we moved further from the Equator, to Boston? Boston lies at 42.4 degrees North.

Annual energy output vs panel tilt angle, for a South-facing 5 kW array in Boston