Duh, solar power doesn't work at night — but it excels during the day

The Department of Energy recently criticized solar power on social media for not producing electricity at night, pointing to a July heat wave in the mid-Atlantic when solar output dropped after sunset. That's true, but it leaves out how much solar helped during the day, when demand and heat are highest.

Texas offers a clear example. During this week's heat wave, the state's grid hit record electricity demand two days in a row, topping 91 gigawatts on Wednesday. Air conditioners were running full blast, but the lights stayed on. Solar, which Texas has built a lot of in recent years, provided more electricity than natural gas for several hours on Tuesday. On Wednesday, solar supplied more than a third of all the state's electricity for a full workday, reaching over 40% at times. It also charged batteries that then set a record for battery output once the sun went down and demand stayed high. That combination of daytime solar and evening battery power helped keep the grid stable and kept prices from spiking.

None of this means solar can run a power grid by itself around the clock. But it does show solar's real value during the hours it works best — which happen to be the hours when air conditioning use, and strain on the grid, is at its peak. For homeowners with solar panels or batteries, or those considering them, this is the kind of daytime performance and evening backup that matters most during heat waves.