With the world going green, the hydrogen story could get explosive. In fact, according to Vantage Market Research, the market could grow from $374.17 million in 2021 to more than $8.7 billion by 2028. All as the global community clamors for clean energy initiatives as part of the climate change battle. Even analysts at Goldman Sachs say clean hydrogen will play a crucial role in reducing emissions and could become a trillion-dollar market by 2050. This outlook alone makes hydrogen stocks worth considering.

Plus, consider this. The Biden Administration is turning to hydrogen as an energy source for vehicles, manufacturing, and electricity generation. In fact, according to Fortune.com, “It’s offering $8 billion to entice the nation’s industries, engineers, and planners to figure out how to produce and deliver clean hydrogen. The aim is to accelerate the availability and use of the colorless, odorless gas that already powers some vehicles and trains.”

Of course, there are many ways to buy hydrogen stocks. Investors can become stock pickers, and do a tremendous amount of research on each name. Or, there’s always a more passive option in the form of exchange traded funds, for investors looking for low-cost diversification.

I’m going to focus on three of the best ETFs holding world-class hydrogen stocks. These are the three I like the most right now in this space.

Defiance Next Gen H2 ETF (HDRO)

One of the best ways to diversify into hot sectors is with an exchange-traded fund (ETF), such as the Defiance Next Gen H2 ETF (NYSEARCA:HDRO). Not only does this ETF offer a good deal of exposure to industry giants, but it does so at a much lower cost. Indeed, the HDRO ETF, which has an expense ratio of 0.3%, trades at less than $9 a share.

With this ETF, investors gain exposure to stocks such as Plug Power (NASDAQ:PLUG), Bloom Energy (NYSE:BE), Ballard Power Systems (NASDAQ:BLDP), FuelCell Energy (NASDAQ:FCEL), ITM Power (OTCMKTS:ITMPF), and dozens more. Also, to be included in this ETF, a company must generate 50% of its revenue from hydrogen and/or a fuel cell project, or be involved in the development of fuel cell or hydrogen sources, according to Defiance ETFs.

Global X Hydrogen ETF (HYDR)

At less than $10 a share, with an expense ratio of 0.5%, the Global X Hydrogen ETF (NASDAQ:HYDR) is another one of the top ETFs focusing on hydrogen stocks to watch.

This exchange-traded fund invests in stocks involved with hydrogen production, with the integration of hydrogen into energy systems, and in the development of fuel cells and other technologies. Some of its top holdings include Bloom Energy, Plug Power, Ballard Power, Fuel Cell Energy, Cummins (NYSE:CMI), and ITM Power, to name a few.

Granted, the HYDR chart is as ugly as ever. But give it time. When hydrogen stocks get red-hot again, so will ETFs like HYDR.

Direxion Hydrogen ETF (HJEN)

Another “ugly” hydrogen ETF to consider is Direxion Hydrogen ETF (NYSEARCA:HJEN). Again, once the hydrogen boom gets hot, so should “ugly ducklings” like HJEN. With an expense ratio of 0.45%, the ETF offers exposure to 30 hydrogen-related stocks. All are involved in production and generation, storage and supply, fuel cell and battery, systems, and solutions, or membrane and catalyst.

Some of its top holdings include Shell (NYSE:SHEL), Bloom Energy, BP (NYSE:BP), Air Products and Chemicals (NYSE:APD), Plug Power, Linde (NYSE:LIN), and Air Liquide (OTCMKTS:AIQUY), for example.

On the date of publication, Ian Cooper did not have (either directly or indirectly) any positions in the securities mentioned. The opinions expressed in this article are those of the writer, subject to the InvestorPlace.com Publishing Guidelines.