What it means
Buying decisions rarely offer a clean comparison. One machine is cheap to buy and expensive to run over four years, another costs far more but lasts seven years and needs less maintenance, and the sticker prices tell you almost nothing useful on their own.
Equivalent annual cost solves this by turning every option into a single annual figure. It takes the present value of all the costs across the asset's life, then converts that lump into the level annual payment with the same present value, much like working out a loan repayment.
The inputs are the purchase price, the annual operating costs, any residual or scrap value at the end, the useful life in years and the discount rate. Getting the life right matters most, because an option's cost is spread over however many years you assume it will serve.
It is the standard tool for replacement decisions, lease-versus-buy questions and fleet planning, and it is widely used in the public sector for infrastructure choices. Its assumption, like the equivalent annual annuity, is that the asset will be replaced with something similar when it wears out.
The main limitation is that it says nothing about the benefits side. If two options deliver different quality, capacity or flexibility, the cheaper annual cost is only part of the answer and should not be treated as the decision on its own.
In practice
Real-world examples.
Example
A council comparing two road surfacing methods converts each into an equivalent annual cost, and finds the more expensive surface is cheaper per year because it lasts eighteen years rather than eight.
Example
A dental practice weighs leasing an imaging machine at $1,400 a month against buying one outright, and uses equivalent annual cost to bring the purchase price, servicing and expected life into a single comparable figure.
Example
A logistics operator decides whether to replace delivery vans at four years or run them to seven, and finds that rising maintenance costs push the annual cost of the older vans above the cost of replacing earlier.
Formula
Calculation
Equivalent annual cost = Present value of total costs / Annuity factor
Annuity factor = (1 - (1 + r) to the power of -n) / r
A packaging business is choosing between two machines, using a discount rate of 8%.
Machine A costs $60,000 to buy, costs $8,000 a year to run and lasts four years.
Annuity factor for 4 years at 8% = 3.3121.
Present value of costs = $60,000 + ($8,000 x 3.3121) = $60,000 + $26,497 = $86,497.
Equivalent annual cost = $86,497 / 3.3121 = $26,115.
Machine B costs $95,000 to buy, costs $5,000 a year to run and lasts seven years.
Annuity factor for 7 years at 8% = 5.2064.
Present value of costs = $95,000 + ($5,000 x 5.2064) = $95,000 + $26,032 = $121,032.
Equivalent annual cost = $121,032 / 5.2064 = $23,247.
Machine B is cheaper by $26,115 - $23,247 = $2,868 a year, even though it costs $35,000 more to buy.Case study
Seen in the real world.
This is an illustrative and fictional example. Pennington Linen Services, an invented commercial laundry, needed to replace an industrial press and had two quotes that looked impossible to compare directly.
The finance manager worked out the present value of all costs for the preferred option at $54,000 over a three-year life, using a 10% discount rate and an annuity factor of 2.4869. That gave an equivalent annual cost of $54,000 / 2.4869, which is $21,714 a year, a figure the operations team could immediately weigh against the revenue the press generated.
The illustrative value of the exercise was in how it changed the conversation. Instead of arguing about which quote was cheaper, the team started asking how many years each machine would realistically last, which turned out to be the assumption that actually decided the answer.
Watch out
Common mistakes.
- Comparing purchase prices alone and ignoring running costs, which often dominate the total over an asset's life.
- Forgetting to include residual or scrap value, which can materially reduce the annual cost of a shorter-lived asset.
- Dividing total costs by the number of years without discounting, which overstates the burden of costs paid far in the future.
Questions
People also ask.
How does this differ from depreciation?
Depreciation is an accounting allocation of the purchase price, while equivalent annual cost is a cash-based decision tool that includes running costs and the time value of money.
Should tax relief be included?
Yes, if the options have materially different tax treatment, the after-tax cash flows should be used so the comparison reflects what the business actually pays.
Can it be used when the options deliver different benefits?
Only with care, because it compares costs alone, so any difference in output or quality has to be valued separately.
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