If standard labour hours were 100 and actual hours are 110, there would be a 10% labor efficiency variance. If this is multiplied by standard wage rate it would show the variance in financial term.
With this background, we can analyse it whether it was avoidable or controllable or not. If avoidable, we can take factory manager to the task and can warn him or her. If the variance persists, he or she can be changed.
If the variance occurred to be power breakdown or machinery problem then we would investigate those areas. For long term solution, own generators can be installed for facing power shortages and preventive maintenance system can be adopted for un-interupeted operations of the machines.