Compare what two products will cost to own
A sale price covers only the purchase. Compare the same period of ownership, including the extras you need and the costs you expect to repeat.
Compare the same ownership period
Example numbers, not live offers or measured running costs. Use the same currency and ownership period for both options. Add costs once and exclude any costs already included in the purchase price.
Build two comparable estimates
- Use the exact model and variant you are considering. Enter its actual checkout price, including tax and delivery if you want them in the comparison.
- Add one-time extras needed for your use: a required attachment, adapter or initial setup purchase. Leave out anything already included in the bundle.
- Add recurring costs for one year. Include only expenses you expect to pay, such as consumables, a required subscription or energy. Enter zero when there is no recurring cost you intend to model.
- Choose the same ownership period for both options. Enter 0.5 for six months or 3 for three years.
Keep a note of where each estimate came from. A replacement-part price alone does not tell you how often it will need replacing. If an expense is uncertain, try both a low and high estimate and see whether the decision changes.
A worked example
These invented figures illustrate the tradeoff; they are not claims about any product. Option A costs $300, needs $40 in one-time extras and has $60 in expected annual costs. Option B costs $450, needs no extras and has $20 in annual costs.
| Period | Option A | Option B |
|---|---|---|
| At purchase, including extras | $340 | $450 |
| After one year | $400 | $470 |
| After three years | $520 | $510 |
| After five years | $640 | $550 |
Option A costs $110 less up front. Option B saves $40 per year in this scenario, so the modeled totals become equal after 2.75 years. If you expect to keep it for only one year, the lower running cost does not recover the higher purchase price.
Check the formulas
Total ownership cost = purchase price + one-time extras + annual recurring costs × years.
When both options have different annual costs, the potential break-even time is (B's purchase price and extras − A's purchase price and extras) ÷ (A's annual costs − B's annual costs). A positive result indicates when their modeled costs meet. If annual costs are equal, the gap between their upfront prices stays constant. A negative result does not represent a future break-even point.
Turn a comparison into a decision
First rule out products that fail a requirement you cannot compromise on: fit, compatibility, accessibility or a feature you need. Then compare the remaining candidates using the same assumptions. A cost advantage is useful only if the product can do the job.
For a robot vacuum comparison, check what its dock includes before budgeting for extras. For e-readers, consider whether your intended books and library service work with the device. The linked comparisons explain their specific tradeoffs and source limitations.
What this model leaves out
Annual expenses are spread evenly and held constant. The calculation does not predict failures, useful life, repair bills, subscription changes, resale value, financing, inflation or the value of your time. Add only costs you can justify, and use scenarios for uncertainty. Fractional years are prorated; an actual annual subscription might charge for a whole year.
If two options are close, check the assumptions that produce the difference before treating one as cheaper. Our research method explains how we separate published specifications, reviewer observations and editorial recommendations.
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