By century's end, climate change will likely shift the peak demand for electricity in Europe from the winters to the summers, as more people use air conditioning to stay cool, researchers have said.
Understanding how demand for power will change in the coming decades as the planet warms is crucial in the 35 countries of Europe, which makes up the world's third largest electricity market.
"We find significant increases in average daily peak load and overall electricity consumption in southern and western Europe," said the report in the Proceedings of the National Academy of Sciences, a peer-reviewed US journal.
Portugal and Spain could expect demand for electricity to rise by between 3% and 7%.
Meanwhile, "significant decreases" are forecast for northern Europe, with a dip of 2-6% in Sweden and Norway.
It said that "the significant polarisation and seasonal shifts in peak demand and consumption have important ramifications".
Power stations may need to adapt or be moved to meet costly peak-generating capacity, new transmission infrastructure may need to be built, and new energy-efficiency policies designed, said the report.
"Total electricity use seem to be smallest on days with a maximum temperature of about 22 degrees Celsius, and increases when this daily maximum temperature either rises or falls," said lead author Leonie Wenz from the Potsdam Institute for Climate Impact Research.
Heat waves can be deadly, and hot summer days can dampen productivity.
"There now is ample evidence that when it's hot outside, air quality suffers, people are more stressed, aggressive, violent and less productive, mortality and crime rates rise," said co-author Max Auffhammer from the University of California, Berkeley.
"All sectors of the economy are affected by thermal stress, from the residential to the commercial, agricultural to the industrial sector."