Where the Five-Year TCO Goes

Where the Five-Year TCO Goes

Ada re-derives this chapter’s own numbers step by step, at full precision

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Ada ADA · CALCULATION AUDIT

Where the Five-Year TCO Goes

The chapter’s top budgeting mistake is pricing an IoT fleet on its Year-1 sticker and then meeting a $200,000 five-year bill — $100,000 in Year 1 and another $100,000 across Years 2 to 5. Device hardware is only $50,000 of that, a quarter of the total, while connectivity, cloud, and maintenance make up the rest. This audit rebuilds the ledger and tests the “hardware is one quarter” claim to ask where the five-year cost actually goes.

Companion to the chapter Why IoT Projects Fail — every number here comes from that chapter.

See the relationship before changing it

The figure reads from left to right. The blue card is recurring operating years. The middle card applies this page's rule. The green card is total cost. Walk the arrows once: set the input, apply the rule, then read the result with its unit.

The retained audit below checks several chapter fixtures. This model keeps those stated values fixed and changes only recurring operating years, so the numeric fixture does not switch without explanation.

Recurring operating years changes total cost An input card leads through the rule TCO = 100 thousand USD in year one + 25 thousand USD x later years to the total cost result. INPUT PAGE INPUT APPLY THE RULE predict calculate check units OUTPUT RESULT
Walk the arrows. Each later operating year adds another fixed service cost beyond the year-one sticker.

Derive the baseline in four named moves

  1. 1

    Name the input. The chapter baseline is 4 years.

  2. 2

    Name the relationship. TCO = 100 thousand USD in year one + 25 thousand USD x later years

  3. 3

    Substitute with units. 100 + 25 x 4 = 200 thousand USD

  4. 4

    Read the result. Keep the unit beside the value. Use it only inside the technical boundary on this page.

Predict, then change recurring operating years

Try Predict the direction of TCO = 100 thousand USD in year one + 25 thousand USD x later years. Test another recurring operating years, then compare total cost.

4 years
Chapter baseline
Total cost

Observe Each later operating year adds another fixed service cost beyond the year-one sticker. Reset recurring operating years to 4 and compare total cost.

Explain Each later operating year adds another fixed service cost beyond the year-one sticker.

Check yourself

What should you do before trusting a moved-control result?
Answer: Predict its direction, apply the shown relationship, keep the units, and reset to the worked baseline.
What does this small model leave out?
Answer: Only recurring operating years moves here. Field effects named in the technical boundary stay fixed.

Honesty note. This teaching model changes only recurring operating years. It is not a field prediction.

TryRecompute Years 2 to 5 operating cost: 25,000 per year x 4 years = 100,000 dollars.
ObserveTrack Five-year TCO: 100,000 (Year 1) + 100,000 (Years 2-5) = 200,000 dollars.
ExplainExplain Hardware (devices) share: 50,000 / 200,000 = 0.25 = 25%, precisely the "hardware is one quarter" claim; connectivity is the largest single slice at 60,000 / 200,000 = 30%.

Ready: use the stated baseline inputs, then compare each displayed result.

Ada: The chapter’s headline pitfall is budgeting only Year 1 and then being surprised by a $200,000 five-year bill for a 1,000-sensor fleet. Let me rebuild that total and test the “hardware is only a quarter” claim against the cost breakdown.

  • Years 2 to 5 operating cost: 25,000 per year x 4 years = 100,000 dollars
  • Five-year TCO: 100,000 (Year 1) + 100,000 (Years 2-5) = 200,000 dollars

Now the category shares from the breakdown — connectivity $60K, devices $50K, cloud $40K, installation $25K, maintenance $25K:

  • They sum to 60,000 + 50,000 + 40,000 + 25,000 + 25,000 = 200,000, matching the total exactly.
  • Hardware (devices) share: 50,000 / 200,000 = 0.25 = 25%, precisely the “hardware is one quarter” claim; connectivity is the largest single slice at 60,000 / 200,000 = 30%.

The arithmetic makes the trap visible: three-quarters of the lifetime cost is the connected-service tail — connectivity, cloud, and maintenance — that a hardware-only budget never counts, so approving a fleet on its Year-1 sticker price under-funds it by roughly a factor of two.

Every number above is taken from the chapter’s own material and re-derived step by step.

Technical boundaries. This five-year TCO ledger deliberately does not simulate inflation, failures, tariff growth, or discounted cash flow. It adds the fixed Year-1 and four recurring-year costs and reports each category's share.