Utility companies, such as electric, water, and gas providers, have long been a staple of income-focused investors. This is because of the nature of the companies in this industry. Utility companies simply provide a staple of modern living to many, if not all, of the households and businesses in their service area, and these households and businesses mail a monthly check to the utility company. This provides a reliable source of cash flow for utilities.

The utility company, meanwhile, generally does not have to spend particularly large amounts of money to generate growth, because by the nature of their businesses, growth is largely limited to the growth of the population in their service areas. This frees up a significant amount of cash, which can be returned to investors in the form of dividends.

Low interest rate environment hurts yields
Unfortunately, the low interest rate environment that has persisted in the United States over the past few years has resulted in the dividend yields of many utility stocks falling. This is not because the utility companies have been forced to cut their dividends, but is instead because low rates have forced income-seeking investors into high dividend-paying stocks in order to meet their income needs. This has forced up the price of these stocks and consequently forced down the yields.

Three utilities that still have high yields
Fortunately, some utility companies still boast somewhat strong dividend yields. Here are three that yield over 4%:

Company Dividend Yield
Consolidated Edison (NYSE:ED) 4.60%
Southern Company (NYSE:SO) 4.80%
Duke Energy (NYSE:DUK) 4.40%

Let's take a closer look at one of these companies, Consolidated Edison.

Primary energy supplier to growing metropolitan area
Consolidated Edison is the primary provider of electricity and a supplier of natural gas to the New York City metropolitan area. The company provides electric service to 3.3 million customers and gas service to 1.1 million customers in New York City alone. The company also has customers in both eastern Pennsylvania and northern New Jersey.

For decades, consolidated Edison's focus on New York City served as somewhat of a headwind for it, as New York City had been suffering from a decades-long population decline. From the middle of the twentieth century until 2010, New York City lost more people than it gained through migration patterns. Consolidated Edison persevered through this trend however, successfully increasing its dividend every year for the past 41 years.

The fact that the city is now seeing more people moving into it than out of it will likely strengthen the company's ability to continue this dividend growth. This is because a growing population will demand greater amounts of electricity to power their homes and businesses. While there is no guarantee that all of these new immigrants will become customers of Consolidated Edison, some of them certainly will, and that should result in top-line revenue growth, which will allow for further dividend growth.

Foolish takeaways
Consolidated Edison's long history of dividend growth, combined with its strengthening potential to do so in the future, can be very important to those investors who need income from their portfolio, such as retirees. This is because the compounding effects of inflation rob your income of purchasing power each and every year. If the prices of the things that you buy continue to increase but your income doesn't, then your standard of living will continue to fall.

The only way to overcome this is to continuously grow your income, and companies with growing dividends such as Consolidated Edison can help you do just that.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.