California invested heavily in solar and wind starting more than a decade ago. So far in 2024 renewable sources have met 100% of the state's energy needs for at least part of the day since early March, and continuing through the time of this writing in August 2024.
Solar growth in particular has been robust enough that it started to perturb the operation of the grid nearly a decade ago, the infamous duck curve where demand seemingly drops in the middle of the day:
A great deal of solar capacity in California has been installed by property owners on their rooftops, both residential and commercial, fed directly into the electrical panel of a building. This supplies energy to the building without the grid seeing anything at all. From the perspective of the power grid the demand for electricity simply drops during summer afternoons, more every year as more solar panels are installed on more rooftops.
However California is experiencing something new in 2024: the duck no longer has a head. Or at least, the use of methane to supply power to the head of the duck has abruptly fallen.
The dip in the middle of the day is still there, a reduction in demand due to rooftop solar generation. However where methane power generation used to spring back up in the late afternoon as solar production falls off, in 2024 the demand only rises partway back above its low point. The head of the duck is no longer there.
The difference is that the capacity of battery storage on the grid has risen rapidly and passed a tipping point. Much of the late afternoon demand can now be supplied from solar sources, shifted in time using batteries.
California's tax incentives now aim for the installation of more battery capacity. Property owners are free to install solar panels on their rooftops to meet their own demand, but the state doesn't need more solar generation and panel prices have dropped well below the prices where tax incentives were essential. Adding more battery capacity will allow the state to continue to carve the duck, by timeshifting more of the prodigious solar power generation to be ready after the sun sets.
Like solar on the roof, batteries installed in a building appear to the grid as though demand is lower. In reality the demand for electricity is not lower, it is simply being satisfied by batteries before the electric meter sees it. Where we've already seen a reduction in gas generation, we'll begin to see a flattening of the demand curve as the buildings on the grid gradually power themselves for even more hours per day.
