A household in Texas, United States. This is a settlement statement sent by an electric utility company: "You're getting paid for your solar!" It earned $123 this month and $1,200 to date. This home does not just buy and consume electricity, but earns money by selling it. The secret lies in this box—a suitcase-sized container that transformed this house.


Doesn't this seem strange? South Korea is a global battery powerhouse. Yet why don't our homes have systems like this? To find the answer, I visited Texas. This is homeowner Craig Kincaid. A year and a half ago, he installed 50 solar panels on his roof and four battery Energy Storage Systems (ESS) in his storage shed to store electricity. The total cost was around 50 million won (approx. $37,000), and the results were clear. His electricity bills, which previously ran between $400 and $500 a month—over 600,000 won—now amount to just $20 to $30, or roughly 30,000 to 40,000 won. Here is why he invested such a significant sum.
 
Texas experiences everything from tornadoes and hurricanes to severe winter cold snaps. As a result, power outages are frequent. However, this home keeps the power running even when the entire neighborhood goes dark. This was demonstrated on the day of the World Cup final.
 
This was possible because the electricity generated by the rooftop panels during the day had been stored in these batteries. And all of this is managed right inside a smartphone. In real time, the homeowner can see how much electricity the rooftop panels are generating, how charged the batteries are, and whether the house is currently buying or selling power.


On sunny days, surplus electricity is sold back to the power company. Under Kincaid's rate plan, electricity sold is credited against the bill at the exact same rate as electricity purchased. That is how he earned the $1,200 mentioned earlier.
  This raises a question: Can installing only batteries without solar panels still be profitable? The CEO of a residential battery company in Texas uses only batteries at his home without solar panels, charging them when electricity is cheap and drawing power when prices are high. It serves as a refrigerator where you buy items when cheap, store them, and consume them when prices rise. The difference in electricity rates turns into profit. Furthermore, the price of this 'refrigerator' itself has dropped significantly. The secret lies in changed battery materials. In the past, expensive metals such as nickel and cobalt were used. Today, lithium iron phosphate (LFP) batteries are the mainstream. Iron and phosphate are common, inexpensive materials. While their energy storage capacity is slightly lower, that is hardly a drawback for storage units placed next to houses or power plants. Instead, they are cheaper and pose a relatively lower fire risk. South Korean battery companies are also shifting to LFP, and a domestic firm supplies the batteries for Kincaid's provider. However, there is a twist in this market.
 
Solar electricity generates a surplus during the day, while usage peaks in the evening. If you cannot sell it, it gets wasted, so the idea is to store and use it. Whether you make money by selling when permitted or save money by storing when selling is not an option, you come out ahead either way. And this lucrative model is not limited to households. This is the Arizona desert.
 
One of the largest hybrid power generation complexes in the United States is currently under construction. The batteries deployed here are also manufactured by a South Korean company at its U.S. facility. The way this complex operates is identical to that home in Texas: storing power during the day and discharging it when demand rises. Only the scale is different.
   
Power plants are not the only places requiring batteries. Two hours away by car is Phoenix. In this city, rising as the 'Silicon Valley of the desert,' TSMC's semiconductor plant, a domestic firm's battery factory, and AI data centers are converging. Here is what the director overseeing business attraction for the City of Phoenix said.
 
So where do they get that electricity? In this region, the answer lies in the sky. The sun shines brightly for over 300 days a year.
 
Electricity has become a core element of urban competitiveness. Operating a single large data center consumes as much electricity as a medium-sized city. The questions you ask ChatGPT are also processed in places like these. While building a power plant takes 5 to 10 years, a data center can be erected in just 1 to 2 years. Consequently, power supply struggles to keep pace with demand. Batteries are stepping in to bridge that exact gap.
 
As a result, the market has exploded. ESS batteries supplied globally in the first half of this year surged by 71% compared to the first half of last year.
  Now, let us return to the first question. Why doesn't South Korea, which excels at making batteries, have them in our homes? While searching for the answer, an unusual fact emerged. South Korea does possess giant electricity warehouses. Pumped-storage hydroelectric power—which generates electricity by pumping water to a mountain reservoir and dropping it down—is effectively our country's representative storage system. However, this warehouse operates differently from the Texas home. It pumps water up when power is surplus and releases it downward when needed to balance supply and demand.


However, it is not structured so operators can freely store and sell power based on electricity prices. In other words, it is not that storage devices are lacking, but rather that a market offering fair compensation for services has yet to open. South Korea also wastes electricity. In spring and autumn, power generation exceeds electricity demand, leading to repeated mandatory curtailments or shutdowns of solar power plants. While people in the U.S. save money by storing surplus electricity, South Korea is unable to properly store and utilize surplus power even when it exists.

Why is this? An expert provided this explanation:
 
The key is the tariff structure. In South Korea, residential electricity rates remain virtually the same throughout the day. There is no distinction between 'cheap' and 'expensive' times to buy low and draw high. In other words, there is no incentive to store energy. To motivate action, providers must be able to earn returns commensurate with their work, but that market does not yet exist. However, the government has begun to move.
 
For now, the government has begun securing returns through long-term contracts to introduce batteries and has even started pilot testing power trading on Jeju Island. Now, let us look back at that screen from Texas: "You're getting paid for your solar!" South Korea is already manufacturing the batteries. All that remains is establishing a market that allows that sentence to appear on our own utility bills as well.