The United States is expected to lean on non-hydro renewables -- namely, onshore wind and utility-scale solar -- for an estimated 10% of its total electricity in 2019. That may not seem like much, but it's up from virtually nothing at the start of the century. And the best is yet to come.

A combination of falling costs, improving technology, and supportive state policies make it likely that onshore wind and utility-scale solar will provide at least 30% of America's total electricity by 2030. But it's entirely possible that all renewable power sources -- including hydroelectricity, small-scale solar, and others -- could generate close to half of the nation's electricity by that date.

Getting there requires some help from two emerging technologies in particular: energy storage and offshore wind. Both opportunities are nearing an important inflection point, which means investors may want to the renewable energy stocks positioned to benefit on their radar.

A worker installing rooftop solar panels.

Image source: Getty Images.

Are batteries ready for prime time?

The promise of energy storage is simple to understand: Owners of wind farms and solar farms (or a rooftop solar array) could lean on batteries to smooth out the daily or weekly generation profile of their assets. For example, that could allow a solar asset to deliver electricity to the grid at night and incentivize larger solar farms, since energy storage could capture the "overflow" during the day. But residential and grid-scale energy storage products face a familiar obstacle: cost.

Discussing energy storage costs can be tricky because the economics depend on the application (small-scale vs. utility-scale, short-duration vs. long-duration) and the specific materials used in the device. Therefore, while energy storage only makes good financial sense for a limited number of applications today, there are signs that the technology is beginning to find ways into the crowded energy market.

Tesla (NASDAQ:TSLA) manufactures lithium-ion batteries for both small- and large-scale customers. It deployed a record 477 megawatt-hours of storage across all customer types in the third quarter of 2019, representing year-over-year growth of 99%. Most of the company's business comes from grid-scale projects, which may receive a big boost soon. 

Tesla will begin delivering the Megapack, a 3 megawatt-hour battery for utility and industrial customers, in the fourth quarter of 2019. The size is important, but so, too, is the ability to manufacture it as a single unit. That will bring down the per-unit costs and has the potential to add significant growth to the company's energy storage business in 2020. 

Meanwhile, an increasingly competitive residential market suggests energy storage is beginning to make financial sense for homeowners, too. Enphase Energy (NASDAQ:ENPH) is preparing to launch its third-generation battery system, Encharge, which offers configurations of 3.3 kilowatt-hours and 10 kilowatt-hours. The lithium-ion based system is intended to be coupled with rooftop solar arrays and includes an inverter (the company's specialty), communications, and management software. The smaller unit is modular, allowing for systems to scale with a customer's needs. 

Enphase Energy has high hopes for Encharge. The company estimates its foray into energy storage can increase the revenue per home from $2,000 today to over $10,000 in the near future. And as new products roll out, Enphase thinks it can tap into the entire global residential battery market by 2021, which is expected to be a 3,000 megawatt-hour opportunity that year with hypergrowth potential. 

Offshore wind turbines.

Image source: Getty Images.

Can offshore wind keep its momentum?

The United States only has 30 megawatts of offshore wind power operating today, but the country boasts a pipeline of about 25,000 megawatts and could technically support over 10 times that amount. After a number of false starts and delays over the years, the nearly nonexistent industry appears to be finally picking up permanent wins.

The state of New York, which wants to have 9,000 megawatts of offshore wind spinning by 2035, recently sealed the deal on two projects totaling 1,696 megawatts: Empire Wind from Equinor (NYSE:EQNR) and Sunrise Wind from a company of the same name. Both are expected to come online in 2024 -- and investors will be watching them closely. 

Equinor, formerly known as Statoil, has an ambitious long-term strategy that leans heavily on parlaying its offshore oil production prowess into offshore wind projects. It's off to a fast start. The company and a partner recently won an auction to build a 3,600 megawatt project off the coast of the United Kingdom, pushing its total offshore wind portfolio to 5,550 megawatts of owned and shared capacity. 

Equinor sees a huge growth opportunity in the virtually untapped coastal waters of the United States, especially in the Atlantic, and is positioning itself to reap the first-mover advantage. But there's still a long way to go. 

The contract for Empire Wind specifies electricity at just under $84 per megawatt-hour, double the price of onshore wind in the United States. While the cost for offshore wind should continue falling -- Bloomberg New Energy Finance estimates the global average price fell 32% since 2018 -- the pace of the decline might determine how the potentially gargantuan U.S. market develops.