Now that we've covered the basics of equity and debt financing, we can return to the Weighted Average Cost of Capital (WACC). Recall the WACC equation from the beginning of the lesson:

$$\begin{array}{l}\text{WACC}=(\text{Fractionfinancedbydebt})\times (\text{Costofdebt})\times (1-\text{TaxRate})+\\ (\text{Fractionfinancedbyequity})\times (\text{Costofequity}).\end{array}$$Evaluating the WACC for a company is different than evaluating the WACC for an individual energy project. When the WACC for a company is evaluated, we are often trying to determine (under imperfect information) what a company's costs of capital are. In this case, we would utilize as much financial data as possible in order to estimate the various terms in the WACC equation.

For an individual energy project, the various terms in the WACC equation are determined in large part by the type of investment being made, the type of market (regulated versus deregulated) in which the investment is occurring and the individual company or group of companies making the investments.

The tax rate term in the WACC equation may seem odd. Why discount the tax rate from the cost of debt financing? The reason is that from the perspective of a company, the interest on debt (i.e., the cost of debt) is tax deductible, so interest payments are offset by tax savings.

Let's go through a hypothetical example to see how this works. Suppose that Blumsack PetroServices Amalgamated wanted to invest in a new oil refinery. What sort of cost of capital might Blumsack PetroServices face?

Historically, the petroleum industry has financed around 15% to 20% of its activities through debt (you can see this by going to this "Cost of Capital by Sector" web page and looking at the second-to-last column in the petroleum rows, which shows the ratio of debt to equity for firms in this sector). So, we could estimate that 15% of Blumsack PetroServices' refinery activity would be financed by debt (just to use a single number). Oil company bonds have historically had very high ratings, so we'll assume that Blumsack PetroServices has a long-term bond rating of AAA. Looking online at corporate bond yields, we see that a 20-year AAA corporate bond would have a yield of 3.6% (as of the time of this writing).

If Blumsack PetroServices faced a 35% marginal tax rate, then its cost of debt financing would be 0.036 × (1-0.35) = 0.02, or 2%.

Turning now to the cost of equity financing, we need the return on the safe asset; the market risk premium; and the beta for the petroleum industry. The yield on the 30-year treasury bond was 2.94% at the time of this writing. We can assume a risk premium of 5%, and from the "Cost of Capital by Sector" web page we see that the beta for the petroleum industry is between 1.17 and 1.45 (the beta is in the second column of the table; we'll use 1.45 for this example). Thus, the cost of equity for Blumsack PetroServices would be 0.0294 + (1.45 × 0.05) = 0.1, or 10%.

Assuming that 15% of the refinery was financed through debt and 85% through equity, the WACC for the Blumsack PetroServices refinery project would be:

$$\text{WACC}=0.15\times 0.02+0.85\times 0.10=0.095,\text{or9.5\%}$$The WACC represents the discount rate that a company should use in conducting a discounted cash flow analysis of a given energy project. The reason is that the discount rate represents the opportunity cost of getting something in the future relative to getting something today. Since the WACC represents the average return for an energy project (remembering that that average is weighted across both debt and equity investors), it represents a kind of average opportunity cost for investment in a project.