One of the first things you’re going to ask yourself when considering solar power for your home is: “Which direction should my solar panels face?” In other words, what’s the best direction for solar panels on your roof so that they will produce maximum power?
There are two measurements to consider here: azimuth and tilt. Azimuth is a fancy word for the direction your panels face, while tilt is a measurement of their angle up from horizontal.
If you’re installing solar panels on a roof, the azimuth will be determined by which direction your roof points, and the tilt will likely be fixed based on the pitch of your roof. In some cases, your solar installer will install racks that allow the panels to be tilted slightly to maximize production.
Speaking of the installer: they should be able to tell you pick the perfect placement and explain the reasons for their choice. In general there’s one big rule: if you’re in the U.S. (or elsewhere in the Northern Hemisphere), the best direction for solar panels to face is true south (though there is an exception).
The more sunlight reaches your solar panels, the more electricity you can generate and the more money you’ll be able to save on your electric bill. If your panels face south, they’ll receive light throughout the day. Let’s dig a little deeper to show how to determine true south and look at the best tilt angle for solar panels
The difference between regular ‘south’ (magnetic south) and ‘true south’
When you look at a compass, it’s showing you magnetic south, not true south. What’s the difference? A compass points toward the south pole of the earth’s geomagnetic field. It’s the right general direction—but not exact. The earth has a fluid outer core made of iron and nickel, which pulls the needle of your compass slightly away from true south. The “pull,” or magnetic declination, will vary in direction and strength depending on your location.
The direction solar panels should face is true south, a.k.a. solar south or geographic south. To correct the compass reading, your solar installer will calculate the magnetic declination of your site. True south can also be calculated at noon, when shadows from vertical objects run north-south. Another simple method is to look at your house on Google Earth; after centering the image on your home, you can view the north-south grid lines Google provides. In the View menu, select “Grid”.
(In most places though – true south ain’t all that much different than magnetic south, and facing them magnetic south is almost just as good. At least you’re not facing them north and getting basically zero energy… and yes, we have seen this happen).
Where should you install solar panels if the direction of your roof doesn’t face the south?
If your roof faces east-west rather than north-south, you have a few options. Solar panels facing east or west won’t get as much light as those on a southern-facing roof. One solution is to compensate by increasing the solar collector area, either using more panels or larger collectors. You may also be able to mount the panels on racks that orient them to face south, although this will be more expensive than a standard installation.
(Sorry, we know that’s a buzz-kill for some, but basically it’s too expensive and inefficient from an installation perspective, there are serious wind implications, and well, it just ain’t done barely ever).
Another option is to mount the panels somewhere other than your roof. Although this is more unusual, some people choose to mount panels on a south-facing wall. If you have space in your yard, the panels can also be mounted on the ground. This is less expensive, and also gives easy access to the panels if you need to clean them, brush off snow, or do any other maintenance. Ground-mounted solar panels can even be placed on trackers, which adjust the position of the panels throughout the year in order to maximize the amount of sunlight reaching them. If ground or wall-mounted panels don’t work for you, solar panels can also be mounted on a building near your house, like your garage or a storage shed.
Any of these options can also work well if your roof faces south but happens to be heavily shaded from trees or nearby buildings.
But what about the direction your solar panels should face from an ANGLE perspective?
After finding the best place to install your solar panels, your installer will select the ideal tilt. The angle is calculated based on your latitude. A simple rule to follow in the United states is to multiply your latitude by 0.76, then add 3.1 degrees. That should work from Key West to the northern tip of Maine, and there is only 1 (very large) state that isn’t covered in that range. For more information about optimal tilt of solar panels, check out our friend Charlie’s site that is dedicated to exactly that.
Although most people select a fixed position, it’s possible to adjust the angle based on the seasons to squeeze even more power out of your solar panels. Basically, as you get closer and closer to the equator, the more you want your solar panels to face straight up, and vice-versa, as you get closer to the poles, you want to aim them lower in the sky, but still toward the equator.
Are there any exceptions to this rule?
As with anything in life, there are situations in which this cardinal rule doesn’t hold true—or rather, situations in which it’s advisable to break the rule. In the case of solar panel direction, the reason you’d want to break the rule is if you can get a greater benefit from a different orientation, and that’s the case if you live in a place with expensive time-of-use (ToU) rates.
You see, in many places, electricity consumption goes way up in the evening when people come home from work and school and turn on their air conditioners, microwaves, TVs, and Playstations (or Xboxes, or Wiis, we don’t discriminate). Some electric utilities try to avoid the huge spikes in usage that can occur during these periods by increasing the cost of electricity during them. That’s where solar owners come in.
Having panels on your roof means you’re drawing less electricity from the grid, which means you’re spending less on that expensive afternoon (aka, “Peak”) power. But if your panels are pointed south, they won’t be generating as many kilowatt-hours (kWh) as they could if they were aimed to take advantage of the late-afternoon sun in the western sky.
Here’s an example:
In California, the Sacramento Municipal Utility District (aka SMUD, the best utility name ever) has a new ToU plan for 2016-17 under which super-peak electricity during the summertime (from 4 to 7 pm) costs 30.9 cents/kWh, while off-peak electricity is just 8.67 cents/kWh. That’s a 350% increase, and if you can avoid paying it by having solar meet your needs, you come out way ahead.
ToU rates like this and others in CA are a great way for solar to make more cents (groan).
Connect with a solar expert to see if you can take advantage of ToU billing, or whether you’d be better off with panels on a south-facing roof.
Last modified: February 4, 2020