Definition
Interest expense is the cost of borrowing money. It represents the portion of a loan payment attributable to interest, calculated as the interest rate multiplied by the outstanding loan balance.
Basic Formula
- Interest Expense = Loan Balance × Interest Rate
For amortizing loans, interest expense declines over time as the principal balance is reduced.
Interest vs. Principal
- Interest: Cost of borrowing (tax-deductible in many real estate contexts).
- Principal: Repayment of borrowed funds (not deductible).
Role in Cash Flow
Interest expense reduces cash flow before taxes because it is part of debt service payments. Higher leverage increases interest expense but may amplify equity returns.
Tax Treatment
In most real estate investments, interest expense is deductible, creating a tax shield that lowers taxable income.
Example
If an investor has a $4,000,000 loan at 6%:
- Annual Interest Expense ≈ $240,000 (assuming interest-only)
If the investor’s marginal tax rate is 35%, the tax shield from interest would be approximately $84,000.
Impact of Leverage
- Higher leverage: Increases interest expense and financial risk.
- Lower leverage: Reduces risk but may limit return amplification.
- Floating-rate loans: Expose borrowers to interest rate volatility.
Interest Expense in Underwriting
- Affects Debt Service Coverage Ratio (DSCR).
- Impacts projected cash-on-cash returns.
- Influences refinance and exit assumptions.
Common Pitfalls
- Ignoring interest rate caps or rate resets.
- Underestimating refinancing risk.
- Overleveraging in volatile rate environments.
- Confusing amortization with interest-only payments.