By Gabby Ratner
California’s abundant sunshine and strong climate goals have made it a leader in solar energy. Over the past two decades, solar panels have grown from a small, specialized technology into a major source of electricity for homes, businesses, and utilities across the state. This growth reflects both improvements in solar technology and state policies aimed at reducing greenhouse gas emissions.
Electricity in California has become more expensive later in the day. Specifically between 4 pm and 9 pm, demand is highest, so they increase energy prices during this period. This is primarily due to a phenomenon known as the “duck curve,” which reflects a significant, daily imbalance between high demand and low supply.
The duck curve is a graph of net electricity demand over a 24-hour period that shows a sharp midday drop, the “belly”, followed by a steep evening rise, the “neck”, which makes it look like a duck. This sharp midday drop happens because most people aren’t home in the middle of the day, so there is a surplus of solar energy. Then the steep evening rise occurs as people are getting home and the sun is setting, so they use more energy.
This cost may also increase due to the sudden shift from solar to conventional power, which places significant strain on the electricity grid. Most solar panels in your community will make this switch at the same time, so the system might get overworked. Because of that, it takes more money to make sure your solar panels are working well and efficiently. Also, California utilities are investing heavily in infrastructure and wildfire mitigation, with funding coming from these rates. Specifically in California, they use the upcharge to prevent further fires. Not all of this money will go to the solar panels; some will go to other areas, such as fire protection.
Good ways to avoid these price changes are to run heavy appliances like dishwashers or washing machines before 4 pm-9 pm. Another smart idea is to Pre-cool or Pre-heat your house. So if you use air conditioning or heating, it will be cheaper to adjust your home’s temperature earlier in the day, when rates are lower. Lastly, if you have solar panels, a battery allows you to store surplus energy from daytime hours and use it during the higher-cost evening hours. So then you wouldn’t even need to pay these extra prices, because you would have that extra energy stored up.
This paper has focused primarily on California, but the issue also occurs in other states. Most significantly, Arizona, Nevada, Hawaii, North Carolina, and Massachusetts all have higher rates the later in the day it gets. Some examples of how this affects other places include: in Arizona, utilities such as SRP use TOU plans with peak pricing in the late afternoon/evening, often to align with higher air-conditioning demand. In Nevada and Hawaii, TOU structures are similar, and both are approaching limits in solar penetration, prompting calls for battery storage to handle evening price spikes. In North Carolina, in some seasons, utility companies shift to higher prices in the evening, although their winter peak is in the morning. You should do some research on your state and the pricing there!