Increased use of air conditioners, fans and refrigerators, as well as the lower power output at hydro-electric and nuclear power stations in France, contributed to the problem.
The 2,000 megawatts France needed to import was the equivalent capacity of two large nuclear stations and analysts suggested that the power had come from Germany.
The heatwave demonstrated the need for EDF to invest to ensure energy security said Pierre Gadonneix, EDF chairman.
The French firm plans to invest 20bn euros (£13.6bn) in distribution, transport and production and EDF said it was concentrating on coastal plants, which cope better with rising temperatures than those inland.
