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How good are solar panels if they don’t face south?

Solar panels facing 2 directions

In the northern hemisphere, the sun crosses the sky a little to the south, which means putting solar panels on a south-facing roof is the best way for homeowners to capture the most solar energy. But what if you don’t have a suitable south-facing roof?

Well, when it comes to solar panels, west is second-best.

Go west, young one

West-facing roofs get less sun than those that face south, but it’s not as little as you may think. According to the Concord Consortium, makers of Energy3D solar energy modeling software, a home in Boston, MA with panels that face west would get 80% of the electricity that a house with south-facing panels would. That ratio improves to 82% for homes in Los Angeles, California.

On other words, to get the same amount of electricity as a south-facing installation, a west-facing one would need to be 25% bigger. (25% x 80% = 20%). If you have an unshaded, west-facing roof, you can still install solar panels and save money.

But keep in mind, every house is unique. Your roof orientation, material, and shade profile are all part of what makes your home good or bad for solar panels. Your best bet is to connect with a solar expert near you to see whether your home is right for solar.

When west is best

In the afternoon and evening, people arrive home and turn on all their appliances at the same time. Well, maybe not all their appliances, but the change in energy usage is great enough that utility companies call late-afternoon through evening the “peak” period, because of how much more energy is needed during those times.

In our free-market society, when things are more in-demand, they’re more expensive. The same is true for electricity. It’s costlier for the utility companies to buy energy they need to give to their customers at peak times, and those costs are often passed on using a billing arrangement called “Time-of-Use” (ToU) billing.

Under ToU, energy during peak times is more expensive, and in the summer time, those prices go up even further, because the demand for electricity increases as more people turn on their air conditioners.

Enter solar electricity to save the day!

How solar can help avoid peak demand

On a south-facing roof, the panels produce energy when the sun is high in the sky, but as the evening sets in, that production decreases. If the panels face west instead, they get more energy during the afternoon an evening.

For people on a ToU billing plan, west-facing solar panels can help avoid paying the higher peak rates by providing more energy when the cost would be higher. Here’s a diagram showing the average daily sun for a home at 45° N latitude during the summertime:

average path of the sun during summer at 45 N latitude

The diagram shows how the sun passes over a house with solar panels on the south- and west-facing roof surfaces. Let’s walk you through an average day (August 6th, to be exact):

  • The Sun rises at 5:52 AM, and begins directly shining on the south-facing panels at 8:15
  • At 9:50, the sun is high enough in the sky that the west-facing panels begin to receive some direct light
  • At 1 PM, the sun is shining directly out of the southern sky
  • After 6 PM, the south-facing roof is no longer receiving direct sunlight
  • The sun sets at 8:20 PM, and as long as the west-facing roof isn’t blocked by obstructions, it received light up until the end

(data from 3D Sun-Path and Kesian solar elevation calculator)

Under ToU, summer peak times are typically between 3 and 8 pm. With west-facing panels, you can produce nearly 50% more on-peak electricity.

Here’s a chart with some data from Pecan Street Research Institute that shows how west-facing panels compare to those facing south during peak times:

South vs West solar panels in Autin Texas during peak times

The bottom line

If you can take advantage of ToU billing and you have a suitable south or west-facing roof, you should investigate your solar potential and find a local solar installer near you. A west-facing roof producing 50% more electricity during peak times can actually save you more money than a system of the same size facing south.

Last modified: May 31, 2017

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4 thoughts on “How good are solar panels if they don’t face south?

  1. Anonymous says:

    WANT TO INSTALL PANELS ON MY SOON TO BE MODULAR HOME IN 4-CORNERS AREA. No city services there, so comparisons won’t help me. What’s best way to go about this? How can

  2. Marion Biddle says:

    Hi there. We recently had panels installed on two roofs – one facing southeast and the other facing southwest which means we get power all day as the sun moves across the sky. Southeast panels are also at a steep pitch, so right now the are producing better than the southwestern panels because the sun is low in the sky. I assume that will change as we move into spring and summer next year. We have a SolarEdge Inverter with optimizers and the software allows us to see power by panel and do a playback which shows power usage overtime. It is very cool!

  3. Ben Pinti says:

    I already have solar panels, but after reading your site about a west facing roof, I have some questions, my solar panels face to the east. I am uncertain now if that was the best way to face them and wonder if some extra panels could be placed on my west facing roof?

    1. Ben Zientara says:

      Hi Ben,

      Thanks for writing! Technically, east-facing panels can get as much sun as west-facing ones, as long as there are no other issues like morning fog or clouds, or shade. If you went with a professional solar installer, they probably had a good reason to install panels facing east rather than west. I hope they kept you informed! Do you have any obstructions that cause shade or make it difficult to place panels on your west-facing roof? Does your area have weather patterns that often cause afternoon cloudiness?

      It really depends on your home and your roof, but adding panels to an unshaded west-facing roof can be a great move. If the east-facing panels still produce plenty of energy from the morning and early afternoon sun, the west-facing panels would likely produce energy from mid-morning on.

      If you liked your previous installer, you should check with them again, or use our site to help connect you with another installer.

      Thanks again for your note, Ben!

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