The consumption is 69 million kWh higher than the highest level recorded in 2017.
Power use in northern cities and provinces peaked 339 million kWh on June 22, up 9 percent from the highest level last year.
The Electricity of Vietnam (EVN) said that consumers cranked up their air-conditioners to escape sweltering prolong heat wave, which threatens safety and stability of the electricity operation system, and lead to grid overload.
Since more heat waves have been forecast, the EVN recommended organisations, agencies and local people to use electricity economically, effectively and safely.
Air-conditioners should be set at 26 degrees Celsius to save power, reducing the risk of power overload and surging electricity bills, it suggested.