Weighted Average Cost of Capital (WACC) Explained

What WACC represents

Every pound of capital a company uses has a cost: debt costs interest; equity costs the return shareholders expect. WACC is the weighted average of those costs, with each component scaled by its proportion of total capital. It represents the minimum return the business must generate to maintain its value.

Because interest on debt is generally tax-deductible, the after-tax cost of debt is lower than the headline interest rate. This tax shield means that, all else equal, a company with more debt in its capital structure tends to have a lower WACC — though excessive debt raises financial risk, which in turn pushes up the cost of equity.

Practical uses of WACC

Directors use WACC as the discount rate when calculating net present value (NPV). Any project expected to return more than WACC should, in theory, add value to the business. WACC also appears in company valuations — for example, when discounting projected free cash flows to arrive at an enterprise value.

• Investment appraisal: projects returning above WACC are value-accretive.
• Valuation: WACC is the discount rate in discounted cash flow (DCF) models.
• Capital structure decisions: changes in debt/equity mix directly affect WACC.
• Performance benchmarking: comparing ROIC to WACC shows whether the business is earning above its cost of capital.

Estimating WACC in practice

For private companies, estimating the cost of equity is harder than for listed firms, because there is no observable share price. Directors and their advisers typically use comparable listed companies' betas or build up a required return from first principles. Confirm your WACC methodology with your accountant or corporate finance adviser, particularly when it feeds into a formal valuation or lending document.