Soaring natural-gas and coal prices are forcing power-generation companies and manufacturers to switch to using oil, a trend that could add half a million barrels a day to global demand, the International Energy Agency said Thursday.

In its monthly market report, the IEA increased its global oil-demand forecasts for this year and the next by 170,000 and 210,000 barrels a day, respectively, but added that the cumulative effect of the energy crisis could be as large as 500,000 barrels a day from September through next year’s first quarter.

That increase means that the IEA, which acts as the energy watchdog for the wealthy nations of the Organization for Economic Cooperation and Development, expects the world’s thirst for crude next year to exceed pre-pandemic levels.

Oil prices added to early gains on Thursday following the release of the IEA’s report, with Brent crude rising 1.2% to $84.16 a barrel in early trading. U.S. crude futures climbed 1.1% to $81.35 a barrel, on course to close at fresh seven-year highs. Both benchmarks have increased more than 60% this year, accelerating in recent months due in part to tight supply elsewhere in the energy market.

Relatively weak natural-gas inventories for the time of year and low wind levels in Europe have coincided with the post-pandemic economic recovery, coal shortages in China and the possibility of a cold Northern Hemisphere winter to send fossil-fuel prices soaring. Benchmark European gas prices have leapt 184% in the past three months.

IEA Executive Director Fatih Birol said Wednesday that extreme weather events—such as Hurricane Ida in the Gulf of Mexico, droughts stymieing hydroelectric power in China and Brazil, and widespread flooding—have also contributed to the energy crunch. He added that supply choke points, including pandemic-delayed maintenance work, meant that natural-gas outages are currently 40% higher than average.

As a result, analysts have already observed a rise in the trend known as gas-to-oil switching, whereby power plants that run on oil are fired up or ones that can be converted to run on crude products are being switched over. Goldman Sachs cited this in raising its oil-price forecasts late last month, while energy consulting firm Rystad Energy said it expects the Asian power sector to use 400,000 more barrels a day of oil than it previously did in the next six months.