Are your Home Solar Panels Facing in the Wrong Direction

[Volusiano]

I agree that it may work for some but not others.

It works for me because I only have a choice of east or west facing roof top. I've been on the TOU plan which has on-peak from 1-8pm in the summer time (and 5-9am and 5-9pm in the winter time). So I put all my panels on the west facing side so I can maximize the value of my on-peak rate, which is about 3x the cost of the off-peak rate in the summer. Looks like this article validates my decision. Putting the panels on the east facing side would have generated a little bit more energy in my case just because the panels will run cooler in the morning. But my focus is to produce energy during on-peak time for the most part so I can use it and not have to pay for the high 3x on-peak cost.

Also because my on-peak time in the winter is 5-9am & 5-9pm (no solar energy during these times), any excess rolled over from the summer on-peak bucket can be well used for heating (I use heat pump, no gas) in the winter during the on-peak time.

So, different strokes for different folks. But the article does have a point that orientation for max solar generation should not be the only consideration. You need to combine that with other factors to decide on the VALUE of your solar generation, not just the amount.

[Ian S]

This is an interesting question for sure but there are other factors to consider. Not all utilities have 3-7 pm as their peak time; here in Phoenix, APS has noon to 7 pm or in a very few grandfathered cases, 9 am to 9 pm. After being on the noon to 7 pm with solar and net metering for a full calendar year cycle, I'm convinced that I would actually be WORSE off with more westerly facing solar panels even on the T.O.U. plan! This is because of a combination of factors including the date of the annual true-up, the amount paid for excess banked kWh's, the fact that weekends and holidays are all off-peak, the fact that on and off peak credits are separate (and can never be combined) and the particular energy usage schedule of a particular homeowner. The reason I know I'd be worse off with a more westerly orientation is because with the true-up in December and net metering, my system offsets all of my on-peak usage with the bank drawn down to its lowest ebb in September after which the credits begin to accumulate until the true-up. With a more western orientation, I'd get even more excess on-peak credits at year's end at the expense of off-peak production during the year. The year end credits are at the $0.029 per kWh, far below the cost of either on or off-peak electricity.

I guess that's an advantage of my flat roof: different orientations are simpler to achieve. But for me, I the 180 deg azimuth is clearly best.

[Jason]

We are not suggesting that you get up and change the direction of the panels on your roof. A new study by the Pecan Street Research Institute does make you think about the conventional wisdom that home solar panels should be placed on the southern facing roof to be most efficient. You may not have heard of Pecan Street before, but their study certainly had a way of garnering the headlines with experts coming down on both sides of the argument-and this from a study of just 50 homes. Some may discount the study because the sample was small and because the output over the course of the year is only a couple of percentage points different, but the major issue is in peak load from 3pm to 7pm west-facing solar panel arrays produced 49 percent more electricity during this peak demand time. Now what all of the commentators are missing of course is that most homeowners are not going to be redirecting their houses to the south or west just to capture a few more rays.

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