Installment True Cost — Is 0% Financing Really 0%?
Is "0% financing" really 0%?
5% off for cash, or "0% for 12 months"? Many people pick the installments because there's no interest.
But next to the lowest cash price, the discount you give up is the interest: in this example the true annual rate is 9.58%.
What you get
- Implied APR: 0% plans, long low-payment plans, card installment plans, and down payment plus balloon deals — with discounts, fees, admin charges, balloons and rewards all counted.
- Present-value ranking: ranks the cheapest and most expensive ways to pay at your own opportunity cost, with a 0% to 8% sensitivity table.
- Monthly load check: new plus existing installments as a share of income, flagged above 10%.
- Credit card revolving: paying only the minimum — how long it takes and how much interest you pay; and how much a fixed monthly payment saves.
Who it's for
Anyone about to buy a phone, laptop, appliance, scooter or car, or thinking about a card installment plan. Any country, any product.
How to use
- Download from Capafy — you get a zip file (no need to unzip).
- In Claude, turn on code execution, then upload the zip under Settings → Skills. (Claude Code users: unzip into ~/.claude/skills/.)
- Describe your situation in plain English. Claude asks for the numbers it needs, runs the model, and walks you through the results.
Output and language
Claude explains the results in your language. The Excel workbook and written report are currently labeled in Traditional Chinese; English labels are planned for a future version.
Privacy
Runs locally in your own Claude environment. No external connections, no API keys, and your numbers never leave your machine.
Requirements
A Claude environment that can run Python (e.g. Claude Code, or Claude with code execution enabled). Uses openpyxl; Claude can install it on first run.
Disclaimer
The implied APR is estimated from the cash flows; actual terms are set by the seller's or card issuer's contract. For personal planning only — not financial, investment, tax, or legal advice. No banks or cards are recommended.
