The Duck Curve: The Cute-sounding Energy Problem We’ll Need to Fix

To tackle the problem of climate change, a swift shift to clean energy technologies is underway. And homeowners have become part of the shift by generating clean energy (and saving money) by adopting solar panels

But any change as big as the energy transition comes with some challenges. The National Renewable Energy Laboratory found one years ago: Solar panels produce electricity when demand for it isn’t at its highest, and stop producing in the evening, when demand ramps up. This can create a bit of a problem for the grid, though one that does have solutions, as we’ll explore below. 

If you’re considering solar panels, be sure to research the best solar companies, know how to avoid scams and understand the incentives available to you.

What is the duck curve?

The duck curve is what you get when you plot solar power generation and energy demand on a graph. It’s called a duck curve because it ends up resembling a duck. 

The duck curve, showing rising and falling demand throughout the day.

Do you see the duck?

California Independent System Operator/Screenshot Andrew Blok

There is a small peak in the morning, when energy demand grows as people start their day. This is the duck’s tail. Then there is a drop-off in the middle of the day when many people are out of their homes. This is the duck’s back. By evening, there is an even bigger spike in energy demands before tapering off over the evening. This is the duck’s head and beak.

Why the duck curve matters

The duck curve is important because it highlights a problem for solar power generation. Solar panels operate best in direct sunlight, so they reach their peak production during the daytime when the sun is overhead. This is when demand for electricity is the lowest. 

This wouldn’t matter, except that the grid needs supply and demand need to be in sync in order to function. This means utilities need to ramp up generation at power plants to meet evening demand. As solar electricity means power plants are needed even less during the day, they need to ramp up farther and faster than before.

Solar power is generating tons of excess power when it is not needed but starts to taper off as the sun goes down — right when people are heading home and energy demand increases.

How rooftop solar affects the duck curve

Rooftop solar panels are among the most popular clean energy technologies for residential homes and businesses because they are nonintrusive, relatively affordable, and can even generate enough energy that it can be sold back to utility companies. However, the deployment of these rooftop solar panels also worsens the duck curve.

The more solar panels deployed to help the grid, the more the duck curve deepens because the panels are over-generating during off-hours and are unable to keep up with the peak hours when a ramp-up of electricity distribution is required. Without an efficient or effective way to store solar power and deploy it later, the grid ends up needing to curtail solar energy generation during off-peak hours, which cuts back on the overall benefits provided by solar panels.

More solar coverage from CNET: How to Avoid Solar Scams

This isn’t an issue except for a few days in places with a lot of solar panels, such as California and Hawaii.

Solutions to the duck curve

While the duck curve does present a problem as we ramp up solar power in an effort to clean up our electricity generation, there are solutions that may be able to help mitigate and even eliminate the issues it poses. The biggest potential solution: the ability to store excess solar energy so it can be used during peak electricity demand.

There are a number of projects underway seeking to address this problem, and our storage capacity is improving. Because solar energy technology is getting cheaper, more research and funding is being directed toward storage solutions, and storage is expected to grow by five-fold by 2050. This will help utility companies not only generate solar power, but deploy it when it is needed most and counteract days when solar generation is lower.

The adoption of solar power technology bodes well for efforts to reduce reliance on fossil fuels. That doesn’t mean that it won’t come with its own challenges, but solar power is an important tool in making our electrical grid cleaner, safer, and more efficient. As storage technology improves, the duck curve will lessen and our grid should remain as reliable as ever while being significantly cleaner.

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