There are common questions in the investment industry. How can you tell if a company's project is worth investing in or not? Many people often only look at the expected returns, but in reality, that's not enough because you also need to consider the cost of capital used. That’s where the WACC or Weighted Average Cost of Capital comes in, which is a crucial tool for evaluating the attractiveness of an investment.

WACC tells us how much it costs to raise funds to operate the business. Simply put, it’s the average cost the company must pay to obtain capital for its operations. Most investors use the WACC to assess whether investing in a project is attractive or not.

WACC is derived from two main components. The first is the cost of debt, which is the interest the company pays to banks or financial institutions. The second is the cost of equity, which is the return expected by owners or shareholders from their investment.

Calculating WACC isn’t as complicated as it seems. The formula is WACC = D/V(R_d)(1-T_c) + E/V(R_e), where D/V is the proportion of debt relative to total capital, R_d is the cost of debt, T_c is the corporate tax rate, E/V is the proportion of equity relative to total capital, and R_e is the expected return.

Let’s look at an example from XYZ Company, which has debt of 100 million baht (60%) and equity of 160 million baht (40%). The interest rate is 7% per year, the tax rate is 20%, and the expected return is 15%. Plugging these into the WACC formula gives approximately 11.38%. Comparing this to the expected return (15% > 11.38%), this project is considered attractive.

The lower the WACC, the better, because it means the company has a lower cost of raising funds. However, other factors should also be considered, such as industry, project risk, and company policies. The simple rule is: if the return exceeds the WACC, it’s worth investing; if it’s less, it’s not.

The optimal capital structure is the one that minimizes WACC and maximizes the company’s value. Companies have several options: using only owner’s equity results in a higher WACC, but taking on some debt can lower it because interest is tax-deductible.

However, WACC has limitations. It doesn’t account for future changes, such as fluctuating interest rates, nor does it consider investment risk. Also, calculating WACC can be complex because it requires current data. WACC is only an estimate and can always be subject to inaccuracies.

A key tip for effective use of WACC is to combine it with other financial metrics like NPV and IRR for clearer decision-making. Also, it’s important to update the WACC calculation regularly to reflect changes in interest rates, debt levels, and economic conditions.

In summary, WACC is an important financial indicator for investors. It helps evaluate the profitability of investments and decide on capital structure. But it should be used carefully, considering its limitations and other factors that may affect a company’s financial costs, to make the best investment decisions.