Tesla Motors developed a giant backup power system in South Australia to combat the region's energy crisis, and switched on the battery on Dec. 1. (Jay Weatherill via Storyful)

Less than a month after Tesla unveiled a new backup power system in South Australia, the world's largest lithium-ion battery is already being put to the test. And it appears to be far exceeding expectations: In the past three weeks alone, the Hornsdale Power Reserve has smoothed out at least two major energy outages, responding even more quickly than the coal-fired backups that were supposed to provide emergency power.

Tesla's battery last week kicked in just 0.14 seconds after one of Australia's biggest plants, the Loy Yang facility in the neighboring state of Victoria, suffered a sudden, unexplained drop in output, according to the International Business Times. And the week before that, another failure at Loy Yang prompted the Hornsdale battery to respond in as little as four seconds — or less, according to some estimates — beating other plants to the punch. State officials have called the response time “a record,” according to local media.

The effectiveness of Tesla's battery is being closely watched in a region that is in the grips of an energy crisis. The price of electricity is soaring in Australia, particularly in the state of South Australia, where a 2016 outage led 1.7 million residents to lose power in a blackout. Storms and heat waves have caused additional outages, and many Australians are bracing for more with the onset of summer in the Southern Hemisphere.

The Hornsdale battery system, which uses the same energy-storage tech found in Tesla's electric cars, is one of chief executive Elon Musk's newest projects. In March, Musk, who is known for setting high goals and only sometimes meeting them, vowed on Twitter to deliver a battery system for South Australia's struggling grid within 100 days or it would be free. By early July, the state had signed a deal with Tesla and the French-based energy company Neoen to produce the battery. And by Dec. 1, South Australia announced that it had switched on the Hornsdale battery.

Fed by wind turbines at the nearby Hornsdale wind farm, the battery stores excess energy that is produced when the demand for electricity isn't peaking. It can power up to 30,000 homes, though only for short periods — meaning that the battery must still be supported by traditional power plants in the event of a long outage.

The first electric battery was invented in 1800 and most batteries built since have basically worked the same way. What makes lithium-ion batteries different are the materials that make it lighter, rechargeable and longer-lasting. (Julio Negron,Jorge Ribas/The Washington Post)

A spokesman for Tesla didn't immediately respond to a request for comment.

Nonetheless, the Hornsdale reserve has already shown that it can provide what's known as “contingency” service — keeping the grid stable in a crisis and easing what would otherwise be a significant power failure. And, more important, the project is the biggest proof-of-concept yet that batteries such as Tesla's can help mitigate one of renewable energy's most persistent problems: how to use it when the sun isn't shining or the wind isn't blowing.

"When you think about energy storage, it's not a [power] generation resource," said Stephen Coughlin, the vice president of energy storage platforms at the Arlington-based AES Corporation, which is behind several battery projects in California, the Netherlands and several other countries. "What it's really doing is providing a much-needed injection of reliability and resiliency into the network overall."

Where it can take as much as 10 minutes to spin up a traditional turbine in a pinch, added Coughlin, it's not uncommon to see systems such as Tesla's intervene in fractions of a second.

This isn't Musk's only experiment with large-scale batteries. Last year, Tesla said it had equipped a small island in American Samoa with thousands of solar panels and batteries that could serve the area's 600 inhabitants, shifting them almost entirely off fossil fuels. In October, Musk responded to the hurricane crisis in Puerto Rico by offering to discuss building a solar grid for the island. Parts of Puerto Rico are still without power, months after Hurricane Maria ripped down power lines and other energy infrastructure.

An electric grid consisting of distributed solar panels, paired with a large battery, could prove transformative for some island economies, analysts say. Under normal circumstances, the price of imported fossil fuels can become a drain on local businesses. But the abundant sunshine at tropical latitudes makes solar energy extremely cost-efficient.

"[Big batteries] definitely can be a game changer for island or island-type economies," said Ravi Manghani, director of energy storage at GTM Research, a market analysis firm. "Hawaii, for instance, has one of the highest retail rates in the U.S. [for electricity], and that's because of the cost of shipping diesel or other fuel oils which currently are used by a lot of the existing facilities."

What's more, he added, spreading solar panels out across an island reduces the likelihood of the entire grid going down because of storms.

Other battery projects, including in the United States, have already helped manage spikes in demand. For example, a major 2015 gas leak near Los Angeles that kept some gas-fired plants from producing energy at peak times prompted Southern California Edison and San Diego Gas and Electric to announce energy storage projects that were completed earlier this year, according to Sam Wilkinson, an industry analyst at IHS.

In an April report, Wilkinson highlighted the rapid rise of China and Australia as energy storage leaders.

"For the first time Asia accounts for more than one third of the global pipeline" for energy storage, the report read. "This underscores the importance that China, Australia, South Korea and India are all predicted to have in the global market."