Texas’ grid operator told a power plant to delay repairs ahead of a May heat wave. It was among six that crashed.

On Thursday, Texas’ power grid operator told at least one power plant to delay its scheduled repairs and keep operating to help meet demand during hotter-than-expected May weather.

The next day, the plant went offline anyway when some of its equipment stopped working properly, according to energy giant Calpine, which owns the plant. Calpine declined to identify the plant.

By just after 5 p.m. Friday, the Electric Reliability Council of Texas announced that six power plants had gone down unexpectedly and asked Texans to turn up their thermostats to 78 degrees for the weekend and avoid using large appliances during the hottest hours of the day to reduce strain on the power grid.