This automotive financial comparison tool evaluates the total 3-year out-of-pocket costs and retained vehicle equity between leasing a new car versus financing a purchase. Deciding between a lease and a loan involves weighing lower monthly lease obligations against long-term equity accumulated through ownership.

### Comparative Financial Methodology The calculator compares 36-month net expenditures across both ownership structures:

- **3-Year Lease Total Expenditure ($E_{\text{lease}}$):** $E_{\text{lease}} = \text{downPayment} + (\text{leaseMonthly} \times 36)$. - **60-Month Auto Loan Payment ($M_{\text{loan}}$):** Standard amortizing monthly loan payment on $(\text{vehiclePrice} - \text{downPayment})$ at loan interest rate $r$. - **3-Year Loan Payments ($E_{\text{loan}}$):** $E_{\text{loan}} = \text{downPayment} + (M_{\text{loan}} \times 36)$. - **Remaining Loan Balance ($B_{36}$):** Outstanding principal balance after 36 monthly payments. - **Retained Ownership Equity ($Q_{\text{equity}}$):** $Q_{\text{equity}} = \max(0, \text{residualValue} - B_{36})$. - **Net 3-Year Purchase Cost ($C_{\text{buy, net}}$):** $C_{\text{buy, net}} = E_{\text{loan}} - Q_{\text{equity}}$.

### Worked Numeric Example Suppose a consumer compares lease vs buy options for a $38,000 sedan over a 3-year evaluation window: - **Vehicle Price:** $38,000 - **Down Payment:** $3,000 - **Lease Monthly Payment:** $420/mo - **Loan Interest Rate:** 6.5% APR (60-month term) - **Expected Car Value after 3 Years:** $22,000

**Step-by-Step Evaluation:** 1. **3-Year Lease Out-of-Pocket:** $3,000 + (420 \times 36) = 3,000 + 15,120 = \$18,120$. 2. **Purchase Monthly Loan Payment:** On a $35,000 balance at 6.5% over 60 months, $M_{\text{loan}} \approx \$684.84/\text{mo}$. 3. **3-Year Purchase Out-of-Pocket:** $3,000 + (684.84 \times 36) = 3,000 + 24,654.24 = \$27,654.24$. 4. **Loan Balance after 3 Years:** Principal remaining after 36 payments is $\approx \$15,372$. 5. **Retained Equity:** Expected resale value minus remaining debt: $22,000 - 15,372 = \$6,628$. 6. **Net 3-Year Purchase Cost:** $27,654.24 - 6,628 \approx \$21,026$. 7. **Comparison:** In this scenario, leasing has a net 3-year cost of $18,120 compared to $21,026 for buying, saving approximately $2,906 over 36 months.

### Client-Side Processing Note All loan amortization, lease sums, and equity subtractions compute locally in client JavaScript. No banking credentials, car quotes, or credit numbers are transmitted across any network.