Cost of Capital Interview Questions for Finance

The Weighted Average Cost of Capital (WACC) is the average rate a company must pay to raise capital from both debt and equity investors. It represents the minimum required return to satisfy both lenders and shareholders:

• If the expected return is below the WACC, the project destroys value.
• If the expected return is above the WACC, the project creates value.

The average cost of capital is “weighted” because it reflects the relative proportions of debt and equity in the capital structure. Since interest payments on debt are tax-deductible, the after-tax cost of debt is typically lower than the cost of equity, making debt the cheaper source of financing in most cases.

The Weighted Average Cost of Capital (WACC) is calculated by combining the cost of equity and the after-tax cost of debt. Each part is weighted based on how much equity and debt the company uses to finance its operations.

Formula:

WACC = (Cost of Equity × % Equity) + (Cost of Debt × % Debt × (1 – Tax Rate))

• Cost of Equity: Return required by shareholders, often estimated using models like CAPM (Capital Asset Pricing Model).
• Cost of Debt: The nominal interest rate the company pays on its loans or bonds, before any tax effects.
• Tax adjustment: Since interest payments reduce taxable income, the effective cost of debt is lower. This is why the formula multiplies the interest rate by (1 – Tax Rate).
• Weights: Show how much of the company is funded with debt and how much with equity. These percentages are based on market value, not accounting numbers.

The Cost of Equity is the return that shareholders expect for investing in a company’s stock. It’s typically calculated using the Capital Asset Pricing Model (CAPM):

Cost of Equity = Risk-Free Rate + Beta × Equity Risk Premium

• Risk-Free Rate: Represents the minimum return an investor would expect for any investment, compensating only for the time value of money and assuming almost zero risk of default. In practice, it is usually taken as the yield on long-term government bonds.
• Beta measures how volatile the company is compared to the overall market.
• The Equity Risk Premium reflects how much extra return investors expect over the risk-free rate.

CAPM brings these elements together to show that investors require higher returns for taking on greater market-related risk, as captured by Beta.

Beta measures how sensitive a company’s stock is to movements in the overall market. It reflects the company’s exposure to market-wide risk or in other words, how much the stock moves when the market goes up or down.

Formula:

Beta = Covariance (Company, Market) / Variance (Market)

More precisely, Beta looks at the returns of the company and the market. Covariance shows how these returns move together, while variance measures how much the market’s returns fluctuate. So Beta captures how strongly the company’s performance follows broader market trends.

• Beta = 1 → stock moves in line with the market.
• Beta > 1 → stock is more volatile than the market.
• Beta < 1 → stock is more stable than the market.

Beta is influenced by industry, earnings volatility, and capital structure. For example, tech companies often have higher Betas due to stronger ties to market cycles and investor sentiment, while utilities or consumer staples tend to be more stable.

Analysts usually obtain Beta from financial data providers or estimate it using comparable public companies.

When estimating a company’s Beta, analysts often look at similar companies in the same industry. But these reported Betas already include the effect of each company’s debt. Since more debt increases the risk for shareholders, the Betas must be adjusted to focus only on the company’s business risk.

To make Betas comparable, analysts:

• Unlever peer Betas to remove the effect of debt and isolate pure business risk.
• Relever using the target’s capital structure so the final Beta reflects both its business risk and its financial risk.

This ensures the Beta used in valuation is aligned with the target’s specific risk profile.

Debt can still lower the overall WACC because:

• Debt is cheaper than equity: Lenders take on less risk than shareholders and therefore require a lower return.
• Debt increases equity risk: More debt increases financial risk. Fixed interest payments make earnings more volatile, which raises Beta and the Cost of Equity.
• Interest is tax-deductible: This tax benefit reduces the effective cost of debt.

The key is to maintain a balanced capital structure. Too little debt leads to unnecessarily high capital costs, while too much debt increases risk and can raise both the Cost of Equity and the Cost of Debt. The optimal mix minimizes WACC by balancing cost and risk.

If Beta or reliable market data is unavailable, one common alternative is the Dividend Discount Model (DDM). This method values equity based on expected future dividends.

Formula:

Cost of Equity = (Dividend per Share / Share Price) + Dividend Growth Rate

• Dividend per Share: Expected annual dividend, based on actual or forecasted payouts.
• Share Price: The current stock price.
• Dividend Growth Rate: The expected long-term growth in dividends, estimated from past trends, analyst forecasts, or management guidance.

DDM works best for mature, publicly traded companies with stable dividend policies, such as utilities or large industrial firms. It is less applicable to high-growth firms or M&A cases where dividends are irregular or absent.

The $500 million company would typically have a higher Cost of Equity. Smaller firms are seen as riskier by investors because they usually have less diversified operations, limited access to capital, and greater sensitivity to market shocks.

To reflect this additional risk, analysts often apply a Size Premium on top of the CAPM result. This ensures the Cost of Equity captures the higher perceived risk of smaller companies.

In practice, analysts use WACC in several key ways:

• Discounting free cash flows in a DCF: WACC is used as the discount rate in a DCF model to calculate enterprise value. It reflects the opportunity cost of capital and ensures that cash flows are valued relative to the company's risk.
• Setting a hurdle rate for investments: Companies use WACC as a benchmark to decide whether new projects or acquisitions are worthwhile. If the expected return is below WACC, the investment destroys value.
• Running sensitivity analyses: Analysts adjust WACC up or down (e.g., by 50–100 basis points) to test how valuation outcomes change. This helps assess the robustness of the valuation under different capital cost assumptions.