Employees at Stockton coal mine on the West Coast are taking temporary cuts to their hours.
At a meeting in Westport on Thursday, Engineering, Printing and Manufacturing Union members voted by 118 to 91 to cut their shifts from 12 to 10 hours for the next three months.
Solid Energy is seeking save $32 million.
A proposal to make the change permanent was rejected by union members in December last year.
Solid Energy said the international price for coal is at rock-bottom and Stockton is barely making ends meet.
But a spokesman said the company can't make any guarantees that they will return to the original hours.
The EPMU said its members had no option but to accept cuts to their hours.
Shifts will continue as seven days on and seven days off. But the two-hour cut to each shift means a reduction of 17% in wages.
Buller District Mayor Pat McManus said the company needs to do whatever it takes to make a profit.