Learning path 5 · Topic 25 of 30

Track recovery without confusing it with profit

Payback measures how long receipts take to recover spending. It describes liquidity and exposure, not the total economic value of a project.

Change a scenario. Watch the consequence.
0123456Receipts (+)Expenses (−)

Period 0: −$10,000.00. This is the time-zero cash flow. Periods use the payment interval stated in the model.

-10.0k0-1.0k38.0k6Cumulative net recovery ($)Year
Simple unrecovered balanceDiscounted unrecovered balance · dashed
interpolated simple payback period · yearsPBPs=IA=3.333333,PBPd=4.263267PBP_s=\frac{I}{A}=3.333333,\quad PBP_d=4.263267

Simple payback is reached. Discounted payback ≈ 4.263 years. Fractional interpolation assumes uniform receipt within the recovery year.

Follow the reasoning

Accumulate net receipts without interest for simple payback.

Cash-flow dates and signs are part of the answer. Model values retain precision; displays round money to cents. Illustrative assumptions exclude taxes and inflation unless stated.

01

What the model means

Simple payback sums undiscounted net cash flows. Discounted payback sums cash flows discounted at the chosen rate. For constant annual receipts, simple recovery time is I/A, but only meaningful as a within-life recovery if it lies inside the project horizon.

02

Build the calculation

When cumulative recovery crosses zero between years k−1 and k, interpolation gives (k−1)+unrecovered amount/receipt in year k. This assumes receipts spread within that year. With strict year-end cash flows, the first complete recovery is at the integer year-end. A later negative cash flow can erase an earlier recovery.

∑t=0kCFt≥0  (simple),∑t=0kCFt(1+i)t≥0  (discounted)\sum_{t=0}^{k}CF_t\ge0\;\text{(simple)},\qquad \sum_{t=0}^{k}\frac{CF_t}{(1+i)^t}\ge0\;\text{(discounted)}
Practice with feedback

Set up. Calculate. Explain.

Answer unit: years

Rebuild the starting scenario

Initial investment: 10000 $; Annual net receipt: 3000 $/year; Discount rate: 10 % per year; Number of years: 6 years. Calculate the interpolated simple payback period.

Setup hint

Accumulate net receipts without interest for simple payback.

Open the visual solutionPBPs=IA=3.333333,PBPd=4.263267PBP_s=\frac{I}{A}=3.333333,\quad PBP_d=4.263267
  1. Accumulate net receipts without interest for simple payback.
  2. For discounted payback, discount each annual net receipt before accumulating.
  3. With strictly end-of-year receipts, recovery occurs at the first nonnegative integer year. Both payback measures ignore receipts after recovery and are not worth maximization.
0123456Receipts (+)Expenses (−)

Period 0: −$10,000.00. This is the time-zero cash flow. Periods use the payment interval stated in the model.

-10.0k0-1.0k38.0k6Cumulative net recovery ($)Year
Simple unrecovered balanceDiscounted unrecovered balance · dashed
interpolated simple payback period · yearsPBPs=IA=3.333333,PBPd=4.263267PBP_s=\frac{I}{A}=3.333333,\quad PBP_d=4.263267

Simple payback is reached. Discounted payback ≈ 4.263 years. Fractional interpolation assumes uniform receipt within the recovery year.

Visual solution

Accumulate net receipts without interest for simple payback.

Cash-flow dates and signs are part of the answer. Model values retain precision; displays round money to cents. Illustrative assumptions exclude taxes and inflation unless stated.

Checks allow 0.1% numerical rounding (minimum $0.05 or 0.001 in the stated nonmonetary unit). Interpolated factors and rates are approximations; keep table precision consistent.

Answer unit: years

Transfer the idea to a new scenario

An investment of $14,000 generates $4,000/year for six years, discount rate 12%. Find interpolated simple payback, then inspect discounted recovery.

Setup hint

Accumulate net receipts without interest for simple payback.

Open the visual solutionPBPs=IA=3.5,PBPd=4.815349PBP_s=\frac{I}{A}=3.5,\quad PBP_d=4.815349
  1. Accumulate net receipts without interest for simple payback.
  2. For discounted payback, discount each annual net receipt before accumulating.
  3. With strictly end-of-year receipts, recovery occurs at the first nonnegative integer year. Both payback measures ignore receipts after recovery and are not worth maximization.
0123456Receipts (+)Expenses (−)

Period 0: −$14,000.00. This is the time-zero cash flow. Periods use the payment interval stated in the model.

-14.0k0-2.0k310.0k6Cumulative net recovery ($)Year
Simple unrecovered balanceDiscounted unrecovered balance · dashed
interpolated simple payback period · yearsPBPs=IA=3.5,PBPd=4.815349PBP_s=\frac{I}{A}=3.5,\quad PBP_d=4.815349

Simple payback is reached. Discounted payback ≈ 4.815 years. Fractional interpolation assumes uniform receipt within the recovery year.

Visual solution

Accumulate net receipts without interest for simple payback.

Cash-flow dates and signs are part of the answer. Model values retain precision; displays round money to cents. Illustrative assumptions exclude taxes and inflation unless stated.

Checks allow 0.1% numerical rounding (minimum $0.05 or 0.001 in the stated nonmonetary unit). Interpolated factors and rates are approximations; keep table precision consistent.

Explain the distinction

Why can a payback policy reject a positive-PW project?

Can you defend your setup?

Can you place each amount on the timeline, match the interest period, calculate the equivalent quantity, and state the decision or limitation?

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