Rooftop Solar Panels are Almost all Facing the Wrong Direction

By Sarah Zhang on at

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 electrical grids.

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 mis-aligned 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 maximise 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 Texas found that homes with west-facing systems drew 65 per cent 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 New York 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]