Dividend stocks can be a smart addition to your portfolio, as they provide long-term earning potential as well as a source of passive income.

However, choosing dividend stocks can be challenging. Investing in individual stocks requires a substantial amount of research, and it's often expensive as well.

If you're looking for a less research-intensive approach, investing in a dividend ETF may be your best bet. Each ETF can contain hundreds of different stocks, which instantly diversifies your portfolio and limits your risk. There are many dividend ETFs to choose from, but these three Vanguard powerhouses are a great place to start.

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1. Vanguard Dividend Appreciation ETF (VIG)

The Vanguard Dividend Appreciation ETF (NYSEMKT:VIG) tracks the NASDAQ US Dividend Achievers Select Index, and it includes just over 200 stocks from large companies that have a history of increasing their dividend payment year over year.

This ETF was established in 2006, and since then it has earned an average rate of return of nearly 10% per year. If you were to invest around $300 per month in this ETF earning a 10% annual rate of return, you'd have nearly $600,000 accumulated after 30 years.

Also, this fund has paid quarterly dividends of around $0.50 to $0.60 per share over the past year. That may not sound like much, but each share of this ETF costs around $150. Over time, depending on how much you can afford to invest, you could potentially earn thousands of dollars per year in passive dividend income.

2. Vanguard International High Dividend Yield ETF (VYMI)

The Vanguard International High Dividend Yield ETF (NYSEMKT:VYMI) contains nearly 1,200 stocks from companies around the world that have the potential for above-average dividend yields.

This ETF is on the riskier side, so it's important to assess your risk tolerance before investing. It was established in 2016, making it the youngest ETF on the list. Also, just over one-quarter of the fund is allocated toward emerging markets, which can be volatile but also have more room for growth.

Since its inception, it has earned an average rate of return of around 9% per year. And over the past year, it's paid quarterly dividends of around $0.50 per share. This makes it similar to the Vanguard Dividend Appreciation Fund ETF in terms of returns. However, this ETF carries more risk with the potential for above-average growth over time.

3. Vanguard High Dividend Yield ETF (VYM)

The Vanguard High Dividend Yield ETF (NYSEMKT:VYM) is similar to the previous fund, except it only contains U.S.-based companies rather than international stocks. It includes just over 400 stocks from companies with higher-than-average dividend yields.

This ETF is less risky than its international counterpart, and it also has a longer track record, as it was established in 2006. However, it's also experienced slightly lower returns of around 8% per year, on average, since its inception.

When it comes to dividend payments, though, this fund shines. Over the past year, it has paid quarterly dividends of around $0.70 to $0.80 per share, which can add up substantially over time.

This ETF trades for around $100 per share. Say you've been investing for many years, and you now own 1,000 shares. If you're receiving $0.70 per share in quarterly dividends, that's $700 per quarter, or $2,800 per year in passive income. And the more you invest, the more you can earn in dividend payments.

Dividend ETFs can help you build a healthy portfolio while also creating a source of long-term passive income, making them a smart investment for many people. Before you invest, consider your tolerance for risk to decide which of these ETFs is right for you. By choosing the right investment, you can potentially make a lot of money in the stock market.

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.