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IEA executive director Fatih Birol said in most economies that had taken strong confinement measures in response to the virus, electricity demand declined by about 15%, largely as a result of factories and businesses halting operations.

"With weaker electricity demand, power generation capacity is abundant," he said.

"However, electricity system operators have to constantly balance demand and supply in real time. People typically think of power outages as happening when demand overwhelms supply.

"But in fact, some of the most high-profile blackouts in recent times took place during periods of low demand."

Birol said when electricity from wind and solar was satisfying the majority of demand, systems needed to maintain flexibility in order to be able to ramp up other sources of generation quickly when the pattern of supply shifts, such as when the sun sets.

"A very high share of wind and solar in a given moment also makes the maintenance of grid stability more challenging," he said.

"System operators have developed ways to manage these challenges, but extraordinary developments - such as lockdowns of entire countries during global pandemics - create new tests.

"For example, the abrupt slowdown in industrial and business activity across much of Europe has reduced electricity demand, but it is also depriving power systems of a key source of flexibility."

Birol said under normal circumstances, large-scale electricity consumers such as factories could adjust their usage to help balance the system, however that option was hardly open today.

"This highlights the need for policy makers to carefully assess the potential availability of flexibility resources under extreme conditions," he said.