One of the best investments we can make is in our own knowledge and skill set. With that in mind, this article will work through how we can use Return On Equity (ROE) to better understand a business. We'll use ROE to examine NZ Windfarms Limited (NZSE:NWF), by way of a worked example.

Our data shows NZ Windfarms has a return on equity of 1.4% for the last year. One way to conceptualize this, is that for each NZ$1 of shareholders' equity it has, the company made NZ$0.014 in profit.

See our latest analysis for NZ Windfarms

How Do You Calculate ROE?

The formula for ROE is:

Return on Equity = Net Profit ÷ Shareholders' Equity

Or for NZ Windfarms:

1.4% = NZ$627k ÷ NZ$43m (Based on the trailing twelve months to June 2019.)

Most know that net profit is the total earnings after all expenses, but the concept of shareholders' equity is a little more complicated. It is all earnings retained by the company, plus any capital paid in by shareholders. You can calculate shareholders' equity by subtracting the company's total liabilities from its total assets.

What Does ROE Signify?

ROE looks at the amount a company earns relative to the money it has kept within the business. The 'return' is the amount earned after tax over the last twelve months. The higher the ROE, the more profit the company is making. So, all else equal, investors should like a high ROE. That means it can be interesting to compare the ROE of different companies.

Does NZ Windfarms Have A Good ROE?

Arguably the easiest way to assess company's ROE is to compare it with the average in its industry. Importantly, this is far from a perfect measure, because companies differ significantly within the same industry classification. If you look at the image below, you can see NZ Windfarms has a lower ROE than the average (6.6%) in the Renewable Energy industry classification.

That's not what we like to see. We'd prefer see an ROE above the industry average, but it might not matter if the company is undervalued. Still, shareholders might want to check if insiders have been selling.

How Does Debt Impact ROE?

Virtually all companies need money to invest in the business, to grow profits. That cash can come from issuing shares, retained earnings, or debt. In the first two cases, the ROE will capture this use of capital to grow. In the latter case, the use of debt will improve the returns, but will not change the equity. Thus the use of debt can improve ROE, albeit along with extra risk in the case of stormy weather, metaphorically speaking.

Combining NZ Windfarms's Debt And Its 1.4% Return On Equity

NZ Windfarms has a debt to equity ratio of 0.25, which is far from excessive. Its ROE is certainly on the low side, and since it already uses debt, we're not too excited about the company. Judicious use of debt to improve returns can certainly be a good thing, although it does elevate risk slightly and reduce future optionality.

In Summary

Return on equity is one way we can compare the business quality of different companies. A company that can achieve a high return on equity without debt could be considered a high quality business. If two companies have the same ROE, then I would generally prefer the one with less debt.

But when a business is high quality, the market often bids it up to a price that reflects this. Profit growth rates, versus the expectations reflected in the price of the stock, are a particularly important to consider. So I think it may be worth checking this free this detailed graph of past earnings, revenue and cash flow .

But note: NZ Windfarms may not be the best stock to buy. So take a peek at this free list of interesting companies with high ROE and low debt.

We aim to bring you long-term focused research analysis driven by fundamental data. Note that our analysis may not factor in the latest price-sensitive company announcements or qualitative material.

If you spot an error that warrants correction, please contact the editor at editorial-team@simplywallst.com. This article by Simply Wall St is general in nature. It does not constitute a recommendation to buy or sell any stock, and does not take account of your objectives, or your financial situation. Simply Wall St has no position in the stocks mentioned. Thank you for reading.