In sunny California, solar panels are literally everywhere. They are found in arid, desert landscapes in the Central Valley and are scattered across rooftops in the urban center of Los Angeles. At the last census, the state had installed almost 47 gigawatts of solar energy — enough to power 13.9 million homes and provide more than a quarter of the Golden State’s electricity.
But now the state and its grid operator are facing a strange reality: There is so much solar energy that, on sunny spring days when there isn’t much demand, electricity prices go negative. Gigawatts of solar power are being “chopped” – essentially, thrown away.
In response, California has reduced incentives for solar panels on the roof and slowed the pace of panel installation, but declining economic returns could slow solar energy development in a state that has been trying to transition to renewable energy. And as other states increasingly build solar plants of their own, they may soon face the same problems.
Solar energy has many positive properties: once built, it costs next to nothing to operate; it does not produce air pollution and generates energy without burning fossil fuels. But it also has a big, obvious disadvantage: the sun doesn’t always shine.
How solar energy waste works
Over 15 years ago, researchers at the National Renewable Energy Laboratory were in the midst of modeling a future with widespread solar power when they noticed something strange: With a lot of solar power on a given power grid, the net load — or demand of electricity minus renewable energy – took on a “U” shape. Skyrocketing demand in the morning was replaced by almost no demand in the middle of the day, when solar energy could generate virtually all the electricity people needed. Then, at sunset, demand increased again.
California’s grid operator, known as CAISO, later dubbed this effect the “duck curve.” This is a phenomenon that is most evident in the spring months, when solar panels receive abundant sunshine but there is less demand for heating and cooling.
In recent years, in California, the duck bend has become a vast and deep gorge – and solar energy is not used. In 2022, the state wasted 2.4 million megawatt-hours of electricity, 95 percent of which was solar. (That’s approximately 1 percent of the state’s overall power generation in a year, or 5 percent of its solar generation.) Last year, the state only did this in the first eight months.
Cutting solar power is not technically difficult, according to Paul Denholm, a senior researcher at the National Renewable Energy Laboratory, as it is equivalent to flipping a switch for grid operators. However, throwing away free energy increases electricity prices.
Other states, which have been slower to adopt solar, are starting to experience the same thing. Nevada, which generates 23 percent of its solar energy, has also seen duck curves deepen. Hawaii, which has thousands of homes with rooftop solar panels, has reduced the payments these families receive from the grid.
Beyond the sunny West, many states are still looking to increase rooftop solar power and extend its reach beyond affluent homes, so much so that the Biden administration announced this week $7 billion in grants to provide rooftop solar power to 900,000 households low income.
To cope with the situationCAISO is selling some excess power to neighboring states; California is also planning to install additional storage systems and batteries to hold solar energy until the afternoon.
