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Optimize Your Solar Production

DIY Solar, Solar 101/
Optimize Your Solar Production

The price of solar panels has come down significantly but that doesn’t mean you still shouldn’t try to get the most energy possible from them. The key to optimizing solar panel production is in the installation. We all know to install the solar panels with blue side facing up, but there is a little more to it than that.

It is all about the direction the solar panels are facing (often called Azimuth by people in the solar industry) and the tilt angle which would be the angle from horizontal. If a solar panel is oriented so that the sun hits it directly at a 90 degree angle, it will produce the most possible power but the sun is a moving target. Not only does it move across the sky throughout the day, but it is higher in the sky in the summer and lower in the sky in the winter. Many people don’t realize in North America in summer, the sun rises in the Northeast and sets in the Northwest. In the winter that becomes is Southeast and Southwest. It only rises due East and sets due West on the Equinoxes in March and September.

In order to keep up with the sun, many people think they should make the solar panels move. Solar panel tracking systems have been around for a long time, but they aren’t necessarily practical. For one thing, it would look pretty silly to have one on your roof, not to mention the structural and wind load issues you would be dealing with. Ground-mounted solar tracking systems are a possibility, but you are adding moving parts that typically have 5 year warranties and lots of maintenance to an otherwise passive system with a 25 year warranty. The bottom line is that even if you have room to install one in your yard, a solar tracker will be expensive and a pain in the neck. You might gain 20% production, but it would be cheaper and easier to just install 20% more solar panels.

So now we are back to talking about what fixed orientation gets you the best bang for your buck. The short answer is to face you solar panels due South at tilt angle slightly less than your latitude. That means if you are as far South as San Diego it would be a tilt angle of 32 degrees and if you are up North in Seattle it would be a tilt angle of 47 degrees. If you want to be very particular about it, a lower tilt angle will give you more power in the summer when the sun is higher in the sky and a higher tilt angle will give you more in the winter when the sun is lower.

Another thing to consider is how you are being charged for your electricity. If you are on a “Time of Use” or TOU electric rate, you get charged more for electricity used during the summer afternoon and evening. If that is the case, you may want to face your solar panels West. They will produce slightly less energy overall, but they will produce it at a time when you are paying more per kilowatt hour which is likely to save you more money in the long run. There are also some local rebate and incentive programs that will pay out more for solar panels facing West at a lower tilt angle because that is most beneficial for alleviating stress on the electric grid on summer afternoons when everyone has their air conditioners running.

With all that said, a solar panel facing any direction will still save you money on your electric bill. The difference between a panel facing West and a panel facing South is only about 15%-20% less production. The difference between flat and the perfect tilt angle is only 10% - 15% less. This is why solar panels are generally installed on the roof at whatever direction and tilt the roof is without trying to prop them up with tilt legs up to get a different orientation.

If you want to test out different scenarios, there is a great free program called PV Watts that will calculate output for different directions and tilt angles. You can find it at https://pvwatts.nrel.gov/. When it asks for “Azimuth” just type in the number for the compass heading of the direction the panels will be facing (like 90 for East, 180 for South or 270 for West). It will give you the expected production for each month and the annual total for any scenario that you want to see.

You can also call us at (866) 798-4435 to provide you a free analysis based on your roof's pitch, location, and utility rates. We'll design the optimal system for you!

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