1. Nature of Variable Manufacturing Overheads
Variable overheads are indirect production costs that fluctuate with activity levels but cannot be traced directly to individual units (e.g., machinery lubricants, factory cleaning supplies, or electricity powering production equipment). These costs are typically allocated using a driver base like machine hours or direct labor hours.
 
2. Mathematical Formulas and Core Logic
  • Variable Overhead Expenditure Variance: Measures deviations in the actual price paid for utility and overhead inputs per hour of operation.

“VOH Expenditure Variance” =(“Standard Variable Overhead Rate per Hour” − “Actual Variable Overhead Rate per Hour”)× “Actual Allocation Hours Used”
  • Variable Overhead Efficiency Variance: Tracks the efficiency of the underlying allocation driver. If variable overhead is allocated based on direct labor hours, any waste or speed deficit in labor hours automatically drags down variable overhead efficiency.

VOH Efficiency Variance=(Standard Hours Allowed for Actual Output−Actual Allocation Hours Used)×Standard Variable Overhead Rate per Hour

3. Root-Cause Diagnoses
An adverse expenditure variance indicates that utility rates or supply costs rose, or that supervisors managed indirect resources poorly. An adverse efficiency variance points directly back to problems on the factory floor, such as slow worker speeds or machine calibration delays.
 
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