What's the best direction and angle for solar panels?
Your roof is probably just fine for solar
The sweet spot for solar panels in the continental U.S. is facing roughly south, tilted between 15 and 40 degrees, according to the Department of Energy. That keeps the panels in the sun longer than other setups—which means more electricity per panel per year, and bigger savings on your utility bills.
Even if your roof doesn’t have an ideal layout, solar can still be worth it. We talked to a spokesperson from the DOE’s Solar Energy Technologies Office and a couple of the top installers on the EnergySage Marketplace, and they all agreed: East-west systems can produce plenty of power, and so can panels that are mounted nearly flat, or even at fairly steep angles.
In fact, direction and angle usually aren’t the things that get in the way of a productive rooftop solar installation. The bigger blockers tend to be shading, roof size, local electricity prices, and local solar-power policies.
Below, we'll get into the finer details of the ideal direction and angle for solar panels, how it varies depending on where you live, and what it takes to truly optimize your panels' electricity output.
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South-facing solar panel systems will almost always generate the most electricity. But east-west roofs can work well for solar, too.
The direction is more important than the angle. Angle is rarely a make-or-break factor, and most roof tilts will work fine—though there are some exceptions.
Small roofs, bad solar policies, and heavy shading are all much more likely than the roof orientation to wreck the economics of solar.
The EnergySage Solar Calculator can give you a free, quick estimate of how much you might save on electricity with a rooftop solar panel system.
Economically speaking, most installers find that it's more like two-thirds of single-family and small multi-family houses that are a good fit for solar. Those odds are pretty good.
Solar can make sense on south, west, or east-facing roofs, and anywhere from a flat pitch up to 45 degrees or even a little steeper. There’s a very good chance that at least part of your roof fits that description.
When a roof is a bad fit for solar, the direction and angle are usually not what makes or breaks the project. More often, it’s shading and small surfaces.
“Sometimes I take one look at the aerial photo, and I’m like, there’s way too much shade, and it’s gonna cost 20 grand to remove the trees,” says Jimmy Johns, co-owner at North Coast Solar in Michigan (an Elite installer on the EnergySage Marketplace). “And the roof design is only going to fit maybe six panels. It wouldn’t be enough offset [on your utility bill] to be worth the time to do it.” Chimneys, plumbing vents, skylights, and gables can all eat up productive roof area. Also, local building codes often require a setback of at least a couple feet from the roof’s edge.
That said, solar tends to make financial sense if you can fit at least 8 or 10 panels on a south, west, or east-facing surface without too much shade. Those systems (possibly in combination with a battery) should be able to make enough free electricity to offset the cost of installation in well under a decade.
South-facing panels give you the most bang for your buck because the sun crosses the sky in the south, so the panels get more sunlight. “We tell people that a solar panel costs the same amount regardless of what orientation it gets installed in,” says Aaron Nitzkin, executive vice president of solar at Citadel Roofing and Solar in California (another EnergySage Elite installer). “But the same solar panel facing south will produce more power than a solar panel facing any other direction.”
It’s okay if your roof doesn’t face directly south. Any direction between southeast and southwest will be highly productive. (It might even be beneficial to be a few degrees off of due south—more on that below). “For [solar] arrays that are close to the optimum orientation, the annual energy generation is only slightly reduced,” says a spokesperson from the Solar Energy Technologies Office at the Department of Energy. For example, panels that face 10 degrees west of the ideal direction (aka azimuth) lose less than 1% of their production over the course of a year.
Solar can still make sense on an east-west roof, too. An ideal east-west setup only loses 10 or 15% of its annual production vs. a perfect south-facing system. On a typical rooftop with non-ideal angles, it’s more like a 20% drop in electricity production. Even with that drop-off, it’s likely you’ll still produce enough free electricity to save hundreds or thousands of dollars on utilities per year, and offset the upfront cost of installation in a reasonable timeline.
The details get murkier if you live in a state without great solar incentives, or if your east-west roof has heavy shading or very steep angles. But again, it’s generally not the direction or angle that ruins a roof’s solar potential.
North is the worst direction for solar
Johns in Michigan says that north-facing panels only make sense on “one out of 1,000 installs.” They spend much less time in the sun than panels that face any other direction—and the greater the tilt, the worse the production.
Other installers told us it’s not quite so rare for northerly panels to make some sense. Nitzkin says that because California has ample sunshine and sky-high electricity prices, north-facing panels can sometimes create a good return on investment if there’s no other option, particularly if the installation angle is pretty flat and the compass direction is more like northeast or northwest.
Bill Horbaly, president and CEO at Connected Technology in California (another Elite installer on EnergySage), told us that if all the other productive space is covered, sometimes it’s cost-effective to install tilt racks on a north-facing roof to keep panels in the sunlight for longer.
If the cost of solar keeps falling relative to the price of electricity, there will be more cases where north-facing systems could be worth the cost of installation.
According to the DOE, south-facing solar panels perform best when they’re tilted between 15 and 40 degrees. Residential rooftops in the US seem to be most commonly tilted between 18 and 34 degrees—pretty much ideal.
Even if your roof falls outside of the 15 to 40-degree goldilocks zone, solar panels can often still produce more than enough electricity to be worth the investment.
Panels on a south-facing roof with a typical pitch (0 to 55 degrees) will only lose a few percent of their potential production compared to a roof with an ideal tilt. SETO sent us an example: In San Diego, where the typical roof is tilted at 18 degrees (a 4:12 roof), a south-facing system only loses 2% of its yearly output compared to the ideal angle in that city, which is 30 degrees.
East-west systems can work OK at steep angles, but they work better at shallower angles because they spend more time in the sun during the middle of the day. (In theory, a totally flat setup would be best—but in practice, a small tilt yields the most electricity, because it helps dust, leaves, and snow slide off more easily.) In SETO’s San Diego example again, panels facing east and west at the city’s typical 18-degree roofing pitch will lose 15% and 10% of their production (respectively) compared to south-facing panels with the same tilt.
Even if the solar panels are still productive on steep roofs, they do carry a hidden cost: Installation tends to be more expensive, because the crew will be forced to work slower and more carefully, or they’ll have to rent extra equipment. “The steeper the roof, the more expensive the labor gets,” Nitzkin says. “When a roof is very steep, you often need to utilize scaffolding and the installation goes very slowly—often taking 2x to 4x more time, depending on the steepness.” Johns’ company will sometimes rent a bucket lift or scissor lift when they’re working on a steep roof, which usually costs $500 or $600 extra.
What about flat roofs?
Flat roofs are good for solar because you can always tilt your panels toward the south. A common practice is to mount them at a 15-degree angle—enough of a tilt to keep off the debris and get the panels into the sweet spot for production, but not so much that the wind gets behind them and pushes like a sail.
In parts of the country where flat roofs aren’t super common, it can be tougher to find an installer who will install those systems, but they’re out there. More on flat-roof solar here.
Your roof probably doesn’t match the perfect azimuth and angle for maximum solar production, so the panels won’t produce as much energy as they would under ideal conditions. But it’s the cheapest, easiest way to get a good-enough solar setup onto your home.
If you can put solar near your home with a ground-mounted system, then you can set up a perfectly optimized system that generates the maximum possible energy per panel. Here's how to do it.
The perfect direction: It isn’t always perfectly south (180 degrees)—it can actually vary by a few degrees to the east or west.
In San Diego, the most productive azimuth is actually 190 degrees, or just west of due south. “The reason it’s not due south is that in this location mornings are cloudier than afternoons, so it’s better to face slightly west,” says a SETO spokesperson.
The perfect angle: A common rule of thumb is that solar panels are most productive when they’re installed at an angle to match the local latitude. That’s true “if every day is sunny,” as a SETO spokesperson told us. “But on cloudy days, the optimal angle is zero,” because the clouds diffuse the sunlight throughout the entire sky. Since most parts of the US get a mix of sun and clouds, the most productive angle is actually flatter than the angle of latitude.
So in San Diego, at 33 degrees of latitude, the ideal tilt for solar panels is actually 30 degrees.
(For reference: The southern tip of Florida sits at about 25 degrees of latitude, while the top of Minnesota sits at 49 degrees. Everywhere else in the continental US is somewhere in between.)
With the perfect azimuth and tilt, you’ll likely squeeze out 1-2% more energy over the course of a year than you would if you set up your ground-mount system facing due south, tilted to match the local latitude. You can look up the precise values for your town with the PV Watts tool from the National Renewable Energy Laboratory.
Making the case for steeper angles, toward the southwest
If you can get on a net-metering plan for solar, where you get full credit from your utility company for all the electricity you send back to the grid, then your goal should be to make as much total energy as possible in the course of a year—and the tips and guidelines above will get you there.
On the other hand, if you’re locked out of this consumer-friendly policy, you could actually save more money by producing a little less total energy, and instead trying to boost the output during certain times of day and certain times of the year.
As we covered earlier, if your utility company forces you into a net-billing solar plan and a time-of-use electricity rate plan, you’ll often save money by pointing your solar panels a little further west than the optimal azimuth. You’ll make less electricity overall, but more of it will come during the late afternoon peak demand period, when electricity is most valuable under time-of-use rates.
Steeper angles can also make sense if you want to increase your production during the winter, when the sun is lower in the sky. You’ll give up a little production during the summer, but earn some of it back during the winter. If that’s what you’re after, “the optimum tilt angle is steeper than the latitude—typically 45 to 60 degrees,” according to the SETO spokesperson. Plus, installing panels at a steeper angle also allows snow to slide off of your solar panel array more easily.
If you just discovered that you have a great roof for solar panels, congratulations. You'll still need a certified professional to recommend equipment and install the system. On the EnergySage Marketplace, you can receive free solar quotes from our qualified, vetted installers nationwide, who will design and optimize a solar energy system for your unique property.
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