The unions say that even if Chinese utilities adopt an alternative option of burning natural gas, many jobs will still be on the line.
CLP Power Chinese Employees Union chairman Sze Sang-tai estimates that up to 4000 workers whose jobs are related to the operation of coal units will be affected if coal burning is reduced significantly.
"No matter whether they are workers, contractors or suppliers, their jobs will face uncertainty," Sang-tai told local media.
About 60% of the city's power is generated from coal and most of the generation units at both CLP Power and Hong Kong Electric are powered by coal.
The two power stations employ a combined total of more than 5000 with 80% of those jobs at risk.
The power unions worked with the Federation of Trade Unions to put together a response to the government consultation which would decide the fate of Hong Kong’s coal workers.