Japan’s biggest electric utilities are firing up old fossil fuel power plants and ramping up others that are already operating, pushing to meet demand as power prices hit record highs amid a deadly heat wave.

The deployment of older, dirtier stations that use commodities such as crude and fuel oil highlights the lingering effects of the Fukushima nuclear disaster in 2011, which has left most of the country’s reactors offline as operators upgrade them.

Like many other regions of the world, Japan has been hit by record temperatures in a two-week heat wave, with more than 80 people dying and thousands rushed to emergency rooms.

Surging appetite for power, as households and businesses crank up their air conditioning, has driven utilities to start up old fossil fuel plants that had been mothballed but kept on standby or to boost output at already-operational fossil units.

Kansai Electric Power, which supplies the western industrialized heartland where the heat wave has been most persistent, has started up two old oil-fired units, with a total capacity of 1.2 gigawatts (GW), a spokesman said.

The nation’s second-biggest utility has also run one station fueled by natural gas and another fired by oil at higher-than-planned output levels, he said, adding that Kansai had also received 1 GW of power from five other utilities.

The sweltering weather has driven prices on the Japan Electric Power Exchange for the Kansai region to just above ¥100 per kilowatt-hour this week, the highest on record.

Meanwhile, Tokyo Electric Power Company Holdings, the country’s biggest electricity provider and the operator of the wrecked Fukushima nuclear plant, has run oil, coal and gas plants at rates higher than their typical maximum capacity, a spokesman said.

He declined to say which plants were operating at these levels.

Japan relied on nuclear power for nearly a third of its electricity supply before the Fukushima disaster, but now has just six out of 40 available nuclear reactors running.

And the scorching conditions could be set to stay as July turns to August, typically the hottest month in Japan. Western Japan has a 50 percent chance of experiencing above-average temperatures over the month, the country’s weather bureau said last week.

Chubu Electric Power, the country’s third-biggest utility, sees electricity demand in July and August potentially exceeding initial estimates, President Satoru Katsuno told reporters July 20.

“Our old thermal power plants are working hard. We must get our act together to keep them well-maintained,” he said.