California’s famous “duck curve” began as an engineering success story. It ended as a cautionary tale about public policy.
For those unfamiliar with the term, the duck curve describes what happens when large amounts of solar power flood the electric grid during the middle of the day. Net demand from traditional power plants drops sharply, creating the duck’s “belly.” Then, as the sun sets and people return home, demand rises rapidly, forming the duck’s long neck.
The curve wasn’t a sign that solar had failed. Quite the opposite. It proved that California’s rooftop solar program had been enormously successful.
And that’s where the story took an unexpected turn.
For years, California encouraged homeowners to install rooftop solar through generous Net Energy Metering (NEM) rules. Homeowners who invested thousands of dollars could effectively use the electric grid as a giant battery. A kilowatt-hour sent to the grid during the day could be exchanged for roughly a kilowatt-hour used later.
People responded exactly as policymakers hoped.
Hundreds of thousands of homeowners invested in solar systems. Thousands of electricians, salespeople, engineers, and installers built thriving businesses around that demand. Billions of private dollars flowed into clean energy without the state having to build the systems itself.
Then success created a new challenge.
As more solar came online, utilities argued they were purchasing excess electricity in the middle of the day when wholesale power had become plentiful and relatively inexpensive, while still having to supply customers with higher-cost electricity after sunset. They also argued that customers without solar were bearing a greater share of maintaining the electric grid.
Regulators agreed that the compensation structure needed to change.
Unfortunately, the pendulum swung much farther than many in the industry expected.
Under the newer Net Billing rules, homeowners installing solar today generally receive much lower compensation for electricity exported to the grid. The economics changed almost overnight. Systems that once paid for themselves in four to six years may now require eight to twelve years or more, depending on usage patterns and whether battery storage is included.
The result was predictable.
Residential demand slowed dramatically. Many solar installation companies downsized, merged, or closed altogether. An industry that had expanded rapidly under one set of rules suddenly found itself operating under another.
The irony is difficult to ignore.
California successfully encouraged homeowners to invest in clean energy. When enough people accepted the invitation, the rules changed because the program had worked too well.
None of this means rooftop solar is a bad investment. For many homeowners, it still makes excellent economic sense, particularly when combined with battery storage or high on-site electricity use. Nor does it mean regulators were wrong to recognize that the electric grid had changed.
The lesson is much broader than solar.
Infrastructure investments are measured in decades, not election cycles. Whether the investment is a solar system, a factory, a data center, or a power plant, investors need confidence that the basic economic rules will remain reasonably stable long enough to recover their investment.
Markets can adapt to almost any set of rules.
What they struggle to survive is moving goalposts.
The duck curve was real.
The dead duck was policy uncertainty.
