Cuba’s power grid failed and the entire nation plunged into darkness Friday, less than a day after the government stressed the need to paralyze the economy to save electricity in the face of major gasoline shortages and large-scale, regular outages.

The electricity went out nationwide Friday morning after a failure at a thermoelectric power plant in Matanzas, east of Havana, Cuba’s Energy Ministry said on X.

The announcement came less than a day after the prime minister, Manuel Marrero Cruz, held a late-night television address with state officials to discuss the ongoing electricity crisis, which experts said was the worst the nation — long accustomed to food and electricity shortages — had ever experienced.

For weeks, the country has lacked the fuel to run the power grid, which has left large parts of the nation without electricity for up to 12 hours at a time.

When electricity does return, demand surges, further straining the power grid, Mr. Marrero said on Thursday night as he urged people to cut back on usage.

To ease the strain on the electrical network, officials announced on Thursday night that all schools would be closed until Monday and cultural and nonessential activities such as nightclubs would shutter.