Question: “What is the optimal angle to install my solar panels at?” This is a common query we get as solar installers, and obviously is one we need to consider when installing solar panels for our clients.
Answer: For most residential customers the optimal tilt is flush-mounted on their existing south-facing roof, what ever pitch that is. For flat-roof (typical of commercial) it is usually 30°, we hope to cover why in another posting. For customers building a new structure or ground-mount racking, the optimal tilt depends on: your latitude, shading, weather, and the type of panels installed. In most cases having solar electric panels in Saskatchewan facing directly south with no shading and tilted between 30° and 60° will be within a few percent of optimal annual output. If that is not specific enough for you to design your own racking, or win the bet you made at the pub last night, here is a table of modeled optimums including the annual energy output for various locations in the province and around the globe.
The following is a snapshot of the table: “Solar Electric (PV) Output at Optimal Array Tilt Angle” which shows modeled optimum tilt and output values for solar PV installs in many Saskatchewan, Canadian and world-wide cities. You can click on the image to download the full .pdf image, or click here to open the .pdf in a new window.
Discussion: Although it is possible to model optimum solar panel angle or tilt as well as the expected output, these values are only valid for a very specific (if not hypothetical) install, which is subject to “typical” weather conditions and absolutely no panel shading. In some of our other blog postings, we hope to explore the effect of changing tilt on the expected output of a solar install, some good reasons for using an array tilt angle other than the listed optimum for the majority of our solar installs, and the primary reasons for array output being less than the modeled value.
Source of data: The solar output data presented was generated using the RETScreen software developed for Natural Resources Canada, and available free on the web. RETScreen uses weather and solar irradiation data from a NASA database. Although we find RETScreen to be an extremely valuable tool, it is cumbersome to use, and certainly has its limitations.
Flush roof mounts usually best: For most city residential installs, the best option is to attach the array on a south facing roof. This mounting method generally does not affect the snow or wind loading on your structure, does not introduce any inter-panel shading effects, typically allows snow and debris to readily slide off or be removed from the panels and roof and often provides annual energy output only a few percent less than would be accomplished by racking the panels on top of the roof. In fact, most of the time the extra expense associated with racking the panels is not made up for by any extra output. As a result, the home owner is typically better off to spend any extra money on more flush-mount panels instead of spending it on racking-up a lower number of panels on the same roof.
Shading is more of an issue than panel angle: In virtually all in-city installs we have seen, shading of the solar array has a much larger impact on annual output than the angle of the array itself.
Saskatchewan has a fantastic solar resource: Being lucky enough to be based in Saskatchewan, it is very encouraging to see the extremely high levels of potential solar PV output available to us here. For Solar PV, it is interesting to note that the expected output is not simply a function of hours of sunlight. Specifically cool temperatures and other weather patterns cause the expected annual output from PV systems in Saskatchewan to be significantly higher than virtually all other global locations at the same latitude, and even (surprisingly?) higher than many other cities in the world traditionally associated with sunshine.
What do you think? We encourage you to leave a comment with any general questions, clarifications, etc. or contact us directly to learn more about the optimal install angle for your particular location, or to learn how you can start taking advantage of this amazing energy resource in your own home or business.