What it means
A factory budgets variable overhead of $12 for each machine hour, so if it runs 4,000 hours the flexible expected cost for those hours is $48,000, and actual overhead of $52,000 produces a $4,000 adverse spending variance. The comparison is not with the original static budget for a different level of activity, since using the actual denominator helps separate rate or spending differences from changes in hours used.
OpenStax's managerial-accounting lesson describes this as the variable overhead rate variance, also known as spending variance, and contrasts it with the efficiency variance, using actual hours and the standard variable overhead rate for the spending comparison. The business must define whether its activity base is labour hours, machine hours or another driver and use a consistent rate, because a formula using labour hours with a machine-hour standard rate is invalid even if the figures look plausible.
Variable overhead can include indirect materials, power or supplies that move with activity, so a variance may reflect a price change, unusual use of supplies, a utility tariff or a changed mix of costs, and it is not automatically evidence of employee waste or poor control. Some items do not change neatly with the chosen hours base, so the cost model itself may need revision, and the accounts driving the difference should be investigated before demanding operational cuts.
The efficiency variance addresses actual hours versus standard hours allowed for the output achieved. A factory might spend at the planned rate per hour but use too many hours because of breakdowns, in which case spending variance can be zero while efficiency variance is adverse, and conversely a higher power rate can create adverse spending variance even if the team uses fewer hours.
Together the two variances help explain total variable overhead differences, but neither replaces a review of actual invoices and production records. Standards should be realistic and current.
If energy prices rise for an entire quarter, repeating an adverse variance every month without changing forecasts or investigating contracts adds little insight, yet updating a standard merely to erase an unfavourable result can conceal a problem. Record why the standard changed, when it applies and whether the same activity mix is being compared, separating expected inflation from controllable usage where possible.
Large variances deserve priority, but small ones can signal emerging patterns, so set thresholds by amount and business impact. A favourable result could come from under-maintaining equipment or delaying supplies, which may hurt quality later, and an adverse result could be a deliberate expense to preserve safety, so managers should interpret the sign in context rather than reward every negative number or punish every positive one.
For owners, compute the variance consistently, drill into the underlying accounts and compare it with efficiency and quality measures, assigning corrective action only after identifying a cause that can be influenced, since standard costing is a diagnostic tool, not a verdict on one employee or department.
In practice
Real-world examples.
Example
Higher electricity tariffs create an adverse spending variance at unchanged hours. A plant runs 4,000 machine hours as planned, but its power bill is $3,000 above the standard rate. Finance traces the gap to the new tariff and updates the forecast.
Example
Lower supply prices create a favourable variance while hours remain constant. A purchasing team negotiates cheaper lubricants, reducing actual variable overhead to $46,000 against $48,000 expected. The $2,000 favourable variance is checked to confirm that quality has not slipped.
Example
A breakdown increases hours and affects efficiency even if the spending rate stays on plan. The plant runs 4,500 hours to finish the same output, with overhead at exactly $12 per hour. Spending variance is zero while the efficiency variance is adverse.
Formula
Calculation
Variable overhead spending variance = Actual variable overhead cost - (Actual activity units x Standard variable overhead rate per activity unit)
Worked example. A fictional factory records $52,000 actual variable overhead, 4,000 actual machine hours and a $12 standard rate per machine hour.
- Expected cost for actual hours is 4,000 x $12 = $48,000.
- Spending variance is $52,000 - $48,000 = $4,000 adverse under the positive-is-adverse convention.
Use the same base in both rate and hours. If the factory had instead run 3,500 hours with the same $52,000 of actual overhead, the expected cost would be 3,500 x $12 = $42,000 and the spending variance $10,000 adverse, showing why the actual hours must be used.Case study
Seen in the real world.
This illustrative and entirely fictional example follows Precision Moulding, an invented plastics maker. Its overhead spending variance turned adverse for three months. The production manager first blamed long machine hours, but those belonged to the separate efficiency analysis. Finance compared actual overhead accounts with the flexible amount for actual hours. A new lubricant price and a power tariff explained much of the spending gap, while extra setup time explained an efficiency gap.
Managers reviewed supplier terms and machine scheduling separately instead of treating one variance as one cause. The invented case shows how separating rate and activity produces better questions. After the review, finance split the monthly report into a spending section and an efficiency section, each with its own owner. Purchasing took the spending actions, such as renegotiating the lubricant price, and production took the efficiency actions, such as shortening changeovers. Within two quarters the variances were reported with their causes, not just their signs.
Watch out
Common mistakes.
- Comparing actual overhead with the static original budget instead of actual-hours standard cost.
- Calling extra hours a spending variance without calculating efficiency separately.
- Treating a favourable sign as proof of good quality or sustainable savings.
Questions
People also ask.
What does a positive result mean in this formula?
Actual variable overhead exceeded standard cost for actual activity, so it is adverse.
Is this the same as the efficiency variance?
No. Efficiency compares actual activity units with standard units for output.
What if standards are outdated?
Document and review them while retaining a clear comparison with actual results.
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