Deployment of older, dirtier stations that use commodities like crude and fuel oil highlight 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 other regions of the world, Japan has been hit by record temperatures in a two-week heat wave. It has resulted in more than 80 people dying and thousands rushed to emergency rooms. As households and businesses turn up their air conditioning, there is a surging appetite for power – that has driven utilities to restart old, previously mothballed fossil fuel plants that were 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—that house a total capacity of 1.2 gigawatts (GW), according to a spokesman. The nation’s second-biggest utility has also run one station fueled by natural gas and another one by oil at higher-than-planned output levels, he said. He also added that Kansai had also received 1 GW of power from five other utilities.

The intense, sweltering weather has driven prices on the Japan Electric Power Exchange for the Kansai region to just above $0.90 per kilowatt-hour this week, which stands as 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, according to a spokesman, who 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 operational.

The scorching weather conditions could be set to stay as July turns to August, typically the hottest month in Japan. Western Japan has a 50% 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, told President Satoru Katsuno to reporters on July 20.