The hot weather caused power demand in mid-April to exceed the plan by 5% to 823 million kilowatt-hours, national utility Vietnam Electricity (EVN) said in a report.
So it had to rely on oil-fired power production to bridge the gap, it said.
It has forecast demand to increase by 15% year-on-year between May and July, and if water levels drop in hydropower dams, the northern region could see a shortage of 1,600-4,900 megawatts.
The north typically consumes more power than the southern and central regions during summer, but few new power plants have been built there in recent years.
Most of the new projects are in the central and southern regions, but technical reasons prevent them from transmitting a large amount of power to the north.
Water levels in northern hydropower plants are lower than normal. In fact, 18 large dams were less than 20% full on April 24.
The total water level is estimated to be equivalent to 4.5 billion kilowatt-hours, nearly 48% lower year-on-year.
A coal shortage also poses challenges.
EVN’s coal-fired power plants are reporting that their target production faces a 1.3-million-ton shortfall.
The two main coal suppliers, Vinacomin and Dong Bac, can only provide 46 million tons this year, 11.5% lower than required.
Gasoline production is set to decline by almost 19% year-on-year to 5.6 billion cubic meters this year.
Purchase of electricity from China is likely to be 32% lower than planned at 1.1 billion kilowatt-hours.
"Major changes in power generation sources this year will result in an increase in oil-fired power generation during the dry season," EVN said.