The Belhatow power plant supplies energy to 11.5 million of Poland's households.
Poland's most important power plant remained mostly offline on Tuesday following an outage, requiring the country to import energy from abroad.
Belchatow, about 160 kms south-east of Warsaw, is Europe's largest coal-fuelled power plant and provides up to a fifth of energy in Poland. It supplies energy to some 11.5 million households.
The outage on Monday was caused by a failure that switched off 10 of the plant's 11 units. The remaining unit is connected to a different power station and was unaffected.
Energy imports from Germany and Sweden were needed to fill in for the suddenly missing power.
Poland's chief energy distributor, PGE, said early Tuesday that work had been restored in six of the units, but that restarting them after a total cut was a big challenge.
PGE spokeswoman, Beata Jarosz-Dziekanowska, said the nationwide energy system was working properly and no power shortages were expected.
“As the system's operator, we have the required reserves and we can always use imports” within the European energy network, Jarosz-Dziekanowska said.
The outage underscored the need for a faster diversification of Poland's energy sources, where renewables account for less than 18 per cent of the mix and are chiefly represented by solar.
It was previously taken off the grid in 2015, when a massive heatwave and unprecedented demand for cooling power led to a failure of operations.