Units of Production Depreciation

A Units of Production Depreciation method allocates an asset’s depreciation expense based on actual usage, output, or activity rather than the passage of time. The cost is spread across the number of units produced, hours operated, or miles driven, making it ideal for assets whose value is consumed through activity.

How the calculation works

Under units of production depreciation, you first estimate the total units (or activity measure) the asset will produce or generate over its lifetime. Then each period, you measure actual activity and calculate depreciation as a proportion of that total lifetime activity.

An example. A mining company buys a drill press for $500,000, with an expected salvage value of $50,000. The drill press is expected to produce 100,000 units over its life.

• Depreciable amount: $500,000 − $50,000 = $450,000.
• Depreciation per unit: $450,000 ÷ 100,000 = $4.50 per unit.

Now, each period:

• Year 1: The press produces 8,000 units. Depreciation = 8,000 × $4.50 = $36,000.
• Year 2: The press produces 12,000 units. Depreciation = 12,000 × $4.50 = $54,000.
• Year 3: The press produces 10,000 units. Depreciation = 10,000 × $4.50 = $45,000.

Depreciation expense tracks actual output. If the press sits idle one year, producing zero units, there is zero depreciation that year.

Matching principle and economic reality

The appeal of units of production is alignment with the matching principle—one of the cornerstones of Generally Accepted Accounting Principles. The matching principle says that expense should be recognized when the benefit is consumed. For an asset that produces value through activity, that principle is most accurately reflected by tying expense to that activity.

A mining truck’s value is consumed each mile it hauls ore, not simply because time passes. A factory machine’s useful life is measured in parts produced, not calendar days. For such assets, units of production captures the economic reality better than a time-based method.

This is why units of production is especially common in extractive industries (mining, oil and gas) and manufacturing. It is far less common for buildings or furniture, which deliver benefit fairly steadily over time regardless of how much they are used.

Measurement challenges

The main difficulty with units of production is tracking and forecasting activity. The company must:

1. Estimate total lifetime units at acquisition. For a new drill press, this is an engineering estimate subject to error. If the estimate proves vastly wrong (the machine produces far more or fewer units than expected), the company may need to revise the estimate and adjust future depreciation accordingly.

2. Measure actual units each period. Manufacturing facilities typically track production closely, but measurement can be tricky if the asset produces partial units or if output is measured indirectly (hours run instead of units produced).

3. Handle technological obsolescence. A machine might become obsolete before it reaches its estimated unit production. For example, a factory tool designed to produce 1,000,000 widgets might become uncompetitive after 500,000 units due to new technology. At that point, the company would write down the asset and stop depreciating it using the units method.

Accounting treatment

When recording units of production depreciation, the company:

• Debits Depreciation Expense (on the income statement)
• Credits Accumulated Depreciation (a contra-asset on the balance sheet)

Each period, the deduction appears on the income statement and cumulative accumulated depreciation grows on the balance sheet. The net book value is cost minus accumulated depreciation.

Companies using units of production must disclose the activity measure in their financial statements notes, so readers understand why depreciation varies from year to year.

Tax implications

Under US tax law, units of production depreciation is permitted. However, for tax purposes, the IRS also allows the Modified Accelerated Cost Recovery System (MACRS), which typically uses time-based accelerated methods. A company might use units of production for book accounting but claim larger tax deductions via MACRS.

This divergence creates deferred tax assets and liabilities. If book depreciation is less than tax depreciation in a given year, the company builds a deferred tax liability. Over the asset’s life, the two approaches produce the same total depreciation, but the timing differs, creating timing differences that are tracked in the deferred tax accounts.

Section 179 expensing allows small-business owners to immediately write off certain assets entirely, bypassing depreciation altogether. This may be preferable to units of production for a small manufacturer with modest equipment.

When units of production is most useful

Units of production depreciation is ideal for:

• Extractive industries: Mining operations, logging, oil and gas wells—where output drives value consumption.
• Manufacturing: Heavy machinery, production presses, assembly-line equipment—especially those tied to specific products.
• Fleet vehicles: Trucks and delivery vehicles, where depreciation can be tied to miles driven.
• Leased equipment: When a lessor depreciates equipment leased to others based on actual hours of use or rental activity.
• Specialized machinery: Equipment whose benefit is entirely dependent on production or operation.

It is less useful for:

• Real estate: Buildings provide steady value regardless of how much they are used.
• Furniture and fixtures: Office equipment that depreciate due to time and obsolescence, not use.
• Intangible assets: Patents, copyrights, and trademarks where there is no clear measure of “output.”

Comparison to alternatives

Straight-line depreciation assumes equal benefit consumption each period. It is simpler and more conservative; most companies use it as the default.

Declining balance depreciation front-loads deductions over time, useful for assets that become rapidly obsolete (computers, vehicles) whether they are heavily used or not.

Units of production is unique in tying expense directly to activity. It is more complex to administer but far more accurate economically if the asset’s actual consumption tracks usage rather than time alone.

Revising estimates

As with any depreciation method under GAAP, if the original estimate of lifetime units proves materially wrong, the company should revise the estimate prospectively. The accumulated depreciation to date is not restated; instead, the remaining depreciable base (cost minus accumulated depreciation minus revised salvage value) is allocated across the revised remaining lifetime units.

For example, if a drill press expected to produce 100,000 units has produced 40,000 and the company now believes it will produce only 80,000 total (not 100,000), depreciation per unit going forward is recalculated using the remaining 40,000 expected units and the remaining depreciable base.

See also