solar panel orientation and angle

Solar panel performance: how much does roof orientation and angle matter?

Reading Time: 4 minutes

Many people are under the misconception that they can’t install solar panels on their roof for a variety of reasons, whether because of the material, their location, shade, or the dimensions of their roof. Truthfully, there are many factors that make a roof more or less suitable, but while some roof qualities make them a total no-no for installations, others have a minimal impact on a solar panel system investment. In this article, we’ll review two roof factors that impact the performance of solar panels: orientation and tilt.

Your roof’s orientation

The direction that your roof faces, also referred to as its azimuth angle, is one of the primary factors that determines how much sunshine your solar panels will see over the course of the day. 

Here in the Northern Hemisphere, solar panels are most effective when installed on south-facing roofs. However, even if your roof doesn’t face directly south, they can still produce plenty of electricity – regardless of whether you live in snowy Minnesota or sunny California. Plenty of people install solar panels on east- and west-facing roofs (and save money by doing so!)

Pro tip: Not sure which direction your roof faces? Look your address up on Google Maps! Their grid shows which direction is true south – compare that to your roof’s direction on satellite imagery. 

Why orientation matters with rooftop solar

Generally, solar panels that face directly east or directly west produce about 20 percent less electricity than if they were facing south. This doesn’t mean you won’t save money, but if you’re aiming to cover all of your electricity usage with solar, you may have to install a few more panels than you would otherwise need with a southern-facing system. 

While it is technically possible to install solar panels on the north side of your roof, it’s not the best location for solar production (in fact, it’s the worst) – you’ll likely need to use special mounting so that the panels oppose your roof’s slant in order to generate electricity. This means that they won’t sit flush with your roof, and will still produce relatively little electricity. If a northern-facing roof is your only option, it’s worth considering alternative installation options, such as ground-mounted solar or a carport installation. 

Can’t install solar panels on your roof? Consider community solar. 

Community solar allows you to support renewable energy and save money on your electricity bills without installing any equipment on your property. Check out our Community Solar Marketplace to learn more. 

Your roof’s tilt

Ideally, a fixed, roof-mounted solar energy system should be at an angle that is equal to the latitude of the location where it is installed. However, pitch angles between 30 and 45 degrees will work well in most situations. Fortunately, the angle of your rooftop has a lower impact on solar panel production than the direction your roof faces.

Why angles matter with rooftop solar

Just like other factors that affect production, the financial impact of the slight decreases in solar productivity related to your roof’s slope depends on electricity prices in your specific market. 

To give you an example, EnergySage compared data from two places (New York and Washington, D.C.) and estimated the production levels of solar panels tilted at various angles. What we found was consistent with our investigations into the effects of other variables:

  • Regardless of where you live or the tilt of your roof, adopting solar power provides significant savings.
  • The angle of your roof actually has less impact on solar panel performance than the direction your solar energy system faces.
  • Optimal electricity production occurs when solar panels face south at a tilt equal to 30°. However, even if you lower the tilt of your roof all the way down to 5°, production only decreases by about 10 percent.
Angle/locationAnnual savings*Approx cost of electricity ($/kWh)Avg. annual solar radiation (kWh/m^2/day)Estimated electricity production of a 5kW system (kWh)**Production ratio***
30° angle- New York$1,215$0.204.466,0751.22
5° angle- New York$1,088$0.204.025,4381.09
30° angle- D.C.$822$0.134.696,3231.26
5° angle- D.C.$741$0.134.265,7031.14

* Annual electric bill savings (cost of electricity x electricity produced)
** Assumes an 80% derate factor, 180-degree azimuth, array tilt ~equal to location’s latitude
*** Production ratio (electricity produced/size of system)

You’ll notice above that, if you live in New York where electricity is more expensive, decreasing your panels’ tilt to 5° will lower production by about 10 percent. Although this decreases your optimal annual savings by over $125, you still save nearly $1,090 per year. Because you live in a high cost area, your savings over time will grow even more as electricity prices continue to rise.

In Washington, D.C., the production decrease is slightly greater because the city is further south. However, since electricity prices are only around $0.13/kWh, the economic impact is much less—your annual savings only decrease by about $80 per year. Annual savings in D.C., despite the 5° tilt, are still in the range of about $740 per year.

In addition, property owners can often find additional savings through federal, state and local programs that offer incentives such as tax breaks, rebates or–if you’re in D.C.–solar renewable energy certificates (SRECs). The bottom line is, even if your solar panels don’t sit at the perfect angle, they can still deliver significant financial returns.

Start saving with solar

Remember, you don’t need to live in the sunniest state in the country or have a rooftop that faces directly south to take advantage of the financial benefits of solar – the most important factor in determining your solar savings is how much you pay for electricity. By going solar, you reduce or even eliminate your utility electricity costs, so even if you aren’t perfectly maximizing your electricity production, your solar investment can still pay off in a big way. Use EnergySage’s Solar Calculator today to determine just how much you can save.

2 thoughts on “Solar panel performance: how much does roof orientation and angle matter?

  1. Steve Muller

    Phoenix AZ area – roof faces NW (315 deg), at 5″/12″ tilt. Considering tilting NE side of panels upwards to give a more southernly exposure. How do I calculate the effective angle of panel direction considering both the roof tilt and panel tilt? For instance, as an extreme example, a panel mounted 90 degrees from flat (so on-edge vertical) on a NW-facing roof could actually be facing SW, no matter what the pitch of the roof. Does that mean a panel mounted at a 45-degree angle on that NW-facing roof would actually be pointed straight West, no matter what the pitch?


Leave a Reply

Your email address will not be published. Required fields are marked *