The National Union of Mineworkers (NUM) has announced plans to strike against Eskom.

The union threatened Eskom on Wednesday following the power utility’s announcement to close five coal-powered stations over the next 10 years.

NUM general secretary David Sipunzi said the closure programme would result in 10,000 direct job losses and as many as 40,000 other jobs being lost at stations around country and at the coal mines that supply them.

Sipunzi said the strike will involve all its members employed at Eskom without offering a timetable. The union has about 15,000 members working at the power utility which amounts to almost a third of Eskom’s workforce.

However, the power utility said it cannot afford a strike as it provides essential services to the country.

Eskom is not new to labour strikes as earlier in the year, coal workers protested against President Jacob Zuma’s announcement that Eskom would sign new renewable energy contracts.

Reuters reported that NUM membership has fallen to below 200,000 from some 300,000 in 2012 partly due to lay-offs in the country’s mining sector and poaching from rival unions.

Coal is currently used to generate more than 90 % of the country’s power supply. With plans to expand the country’s power dependency to off-grid solutions, by the time new nuclear power stations come online and with the current assistance of independent power producers, Eskom said the country’s power grid will be stable for years to come.

Closing the five power stations is part of the power utility’s plan to move towards cleaner energy production, and Eskom said that these stations are old and nearing the end of their life.