01 · Purpose and decision scope
Purpose and decision scope
Cost Benefit Analysis compares the consequences of options with a defined counterfactual over a stated time horizon. For an internal warehouse decision, a practical financial version identifies incremental cash costs and savings, timing, and uncertainty. Wider appraisal can also include non-financial and social effects. The purpose is to clarify whether a proposed improvement creates sufficient value and whether that conclusion depends on fragile assumptions.
Use it after a concept is defined well enough to estimate delivery and operating consequences. Prerequisites include a baseline, a horizon, a consistent price basis, and owners who can distinguish released capacity from cash that will actually leave or enter the business. This lesson’s fictional calculation is a local business appraisal, not a claim to apply every requirement of government social appraisal. The Green Book provides authoritative appraisal context; the example’s rate and horizon are explicitly chosen assumptions.
02 · Identify incremental effects without double counting
Identify incremental effects without double counting
Fictional Northbank Dispatch considers early carrier assignment with scan confirmation. It would pay £12,000 at the start for configuration, equipment, and preparation. After stabilization, it expects to avoid £8,000 of overtime cash annually and £2,000 of carrier correction charges annually. Added support and consumables cost £1,000 annually. The assumed net annual cash benefit is therefore £8,000 + £2,000 − £1,000 = £9,000.
The process may also release three hours of staff capacity daily. Northbank reports that capacity separately. It does not multiply the hours by a labor rate and add the result to the £8,000 overtime reduction when they describe the same released work. Only demonstrably additional uses or avoided expenditures belong in another benefit line. A salaried employee’s available time can be valuable without being a payroll saving. The appraisal keeps the operational benefit visible without inventing cash.
03 · Set horizon, prices, and discount assumptions
Set horizon, prices, and discount assumptions
Northbank chooses a three-year horizon because the dispatch software contract is due for review afterward. It assumes constant purchasing-power cash values, no residual value, no tax effects, and benefits at each year-end. It uses a local real annual discount rate of 5% for this illustration; that is not presented as a government-prescribed rate. A nominal appraisal would instead require internally consistent nominal cash values and a nominal rate.
Discounting reflects the timing of cash: a future amount is divided by (1 + r) raised to its year number. Discounting is not a substitute for risk analysis. The team handles benefit uncertainty through alternative scenarios rather than hiding it in an unexplained rate. It also records whether the first year includes ramp-up. Here the base case assumes full £9,000 net benefits in each of years one, two, and three. That assumption must be challenged before authorization.
04 · Worked present-value calculation
Worked present-value calculation
At 5%, the three year-end present values are £9,000/1.05 = £8,571.43, £9,000/1.05² = £8,163.27, and £9,000/1.05³ = £7,774.54. Their total is £24,509.23. Subtracting the £12,000 initial outflow gives a net present value of £12,509.23. Rounding occurs only for display; calculation uses unrounded values. The undiscounted simple payback is £12,000/£9,000 = 1.33 years under the full-benefit assumption.
That result supports further consideration, but it is not proof the change pays for itself. The benefits are estimates, and positive value does not override safety or traceability constraints. The team compares the proposal with continued current operation and with a simpler fixed-lane option using the same horizon and price basis. A benefit–cost ratio would require a stated convention about whether operating costs are netted from benefits or included in the denominator; inconsistent conventions can make comparisons misleading.
05 · Sensitivity and an evidence-based decision
Sensitivity and an evidence-based decision
Northbank tests a conservative case with net cash benefit of only £4,000 annually. The three-year annuity factor at 5% is approximately 2.72325, so present benefits are £10,892.99 and net present value is −£1,107.01. The break-even annual net cash benefit is £12,000/2.72325 = approximately £4,406.50. The decision therefore depends on achieving more than roughly half the base-case annual benefit.
The team asks finance to verify actual overtime that can be avoided, operations to confirm the staffing response, and transport to validate correction-charge records. It examines a delayed first-year benefit and a higher support-cost case. The pilot measures search time and errors, but finance still has to translate operational changes into cash consequences. Northbank proceeds with a bounded test and retains the financial assumptions for later review rather than calling the base-case net present value a realized saving.
06 · Weak versus strong appraisal and advanced use
Weak versus strong appraisal and advanced use
Weak analysis treats all released hours as cash, counts the same avoided rework twice, omits maintenance, or compares options over different horizons. Strong analysis uses incremental effects, states the counterfactual, separates cash from capacity, and shows how plausible changes alter the conclusion. It also reports effects that cannot be responsibly monetized, such as easier recovery or reduced operator frustration, without inventing an arbitrary pound value to force them into the total.
Advanced teams use ranges, scenarios, and probability models when evidence supports them. They distinguish correlated benefits: overtime avoidance and correction charges may both depend on the same volume conditions. They assess reversibility and the value of learning before a large commitment. After rollout, compare realized cash changes with the baseline while accounting for volume, wage rates, and carrier contracts. A good appraisal remains a decision record that can be tested against outcomes, rather than a persuasive spreadsheet abandoned after approval.
07 · Operating conditions and evidence
Operating conditions and evidence
Northbank’s baseline is continued current operation under the same demand and contractual assumptions, not a fictional world with no dispatch costs. The £12,000 investment and the annual net benefits are incremental to that baseline. If existing scanners would otherwise be replaced next year, the appraisal must account for that counterfactual rather than charging the improvement for the whole replacement and also claiming the replacement as a benefit.
Timing deserves separate attention from total amounts. A one-year delay in support readiness can postpone savings while the initial expenditure has already occurred. Likewise, overtime savings may occur only during peak months, even if released capacity exists every weekday. Northbank records the staffing decision that realizes the cash benefit and checks that service remains acceptable afterward. This makes the appraisal a practical operating commitment. Capacity released, expenditure avoided, and customer consequences are related, but their relationship must be demonstrated rather than assumed.
08 · Decision record and next step
Decision record and next step
The financial decision includes a benefit owner. Northbank’s operations manager owns the overtime response, while the transport coordinator owns validation of correction charges. Finance checks whether these changes appear in the accounts and whether volume or contract changes explain part of the result. Without ownership, an attractive estimate can remain a capacity improvement that never becomes the expected cash outcome.
The project also records costs that may fall outside the initial quote. Training backfill, spare batteries, report maintenance, and support during the first collection waves can matter. If already included in the £12,000 or £1,000 annual support assumption, they are not added again. If omitted, the appraisal is revised. Consistency is more valuable than a large number of lines. The final recommendation presents net present value, sensitivity, non-financial consequences, and remaining uncertainty together, enabling a sponsor to assess the decision rather than merely admire a positive total.
| Quantity | Illustrative value | Meaning |
|---|---|---|
| Initial outflow | £12,000 at time zero | Incremental delivery expenditure |
| Annual net cash | £9,000 for three year-end flows | Avoided overtime and charges less added support |
| Released capacity | Three hours per day if the hypothesis holds | Report separately unless distinct cash realization is evidenced |
Connections
Related methods and phase use
Placed under Improve because of the outcome it supports. Use the method in other phases when its purpose and assumptions fit the work; the phase list is a guide to selection, not a compulsory sequence.
Sources
Professional foundations and further reading
The explanation and fictional teaching examples are written for LeanTrainingLab. Linked primary sources provide professional foundations; example values and local conventions are stated in the guide. The accepted toolset draws on Six Sigma+Lean Toolset, second edition (Lunau, editor; Springer, 2013). No book text or examples are reproduced here.