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Rooftop Solar Panels Are Almost All Facing the Wrong Direction

Illustration for article titled Rooftop Solar Panels Are Almost All Facing the Wrong Direction

If you're thinking that solar panels face south to capture the most sunlight and thus the most energy, then you'd be absolutely correct. Yet, solar experts are saying that rooftop panels should be installed facing west. This surprising turn can be explained by quirks in our electrical grid.


As the New York Times explains, not all electricity is created equal. Demand for electricity peaks in the afternoon, especially in the summer when air conditioners are cranking away under the hot afternoon sun. But south-facing solar panels capture the most energy at morning and midday, when there's already ample electricity in the grid. If we just turned our solar panels 90 degrees to face west, their electricity production would match our electricity demand.

If misaligned solar panels can't handle peak demand, we have to rely on plants with more flexible energy sources—the ones burning fossil fuel. Ironically, that means installing solar panels the wrong way can actually make it more important to keep natural gas plants around.


So why do we keep doing it wrong? Bad policy. Currently, solar panel owners are paid by the amount electricity they make, so they have every incentive to maximize it with south-facing panels—even if that's bad for the larger system.

In fact, it's well-known in the solar industry that west-facing solar panels are better for the grid as a whole. A study last year in Austin found that homes with west-facing systems drew 65 percent less electricity from the grid during summer peak demand compared to 54 south-facing systems. Multiply that across thousands of homes, and that's taking off a big load on the electrical grid. A 2010 California Public Utilities Commission report also concluded that west-facing are better at reducing strain on the grid.

As the Times notes, our misaligned solar panels really distill the challenge with renewable energy sources like sun and wind: They can produce a lot of energy, but not necessarily when we need it. This creates an absurd situation when the price of electricity can essentially be negative:

Sometimes the price goes to zero. Oddly, it can go even lower. When demand is very low in the middle of the night and the wind is blowing hard, there may be too much electricity on the system and grid operators will charge generators that want to add more.


It's easy to think of installing solar panels as reducing dependency on the grid, but actually, it's all one big, obscenely interconnected system. [New York Times]

Top image: AP Photo/Jerry McBride


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Or you could just add battery packs. For instance, a single 85kW-h Tesla model S battery pack would keep the average household in the US (Which uses 10,837kW-h/year, or 29.69kW-h/day) running for 2 days, 20 hours. Without any extra power being added from any other source. So you install 40kW or 50kW worth of solar cells on a roof to give yourself a boost and handle not-so-sunny days, and a 40kW wind turbine, for those winter days when it's not sunny at all, and the excess power gets dumped into the battery pack, and once that's full, into the grid, who can use their own battery packs (Which they should have anyway, to handle transient loads).

Or, with that amount of local generation, live completely off-grid. Either works.