IELTS Reading 145: Batteries and the Grid's Missing Flexibility

Adapted from International Energy Agency 2026 Global Energy Review / EIA (2026). IELTS Reading Section 3 difficulty, approximately 1,050 words. Source: https://www.iea.org/reports/global-energy-review-2026

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Reading Passage

A. The transition to renewable electricity faces a problem that the panels and wind turbines themselves cannot solve. Solar farms produce most intensely around midday, yet households switch on their lights and ovens in the early evening, long after the sun has dropped. Wind, similarly, blows hardest at unpredictable hours. A power grid must balance supply and demand at every instant, and although conventional generators can be switched on and off to follow demand, weather-dependent sources cannot. It is here that batteries enter. A battery absorbs electricity when supply is abundant and returns it to the system minutes or hours later, when it is more valuable. This single trick — holding energy in reserve until it is needed — has turned batteries from a niche accessory into one of the central pieces of the clean-energy transition. According to the International Energy Agency, about 108 gigawatts of new battery storage were installed worldwide in 2025, roughly forty percent more than the year before, and about four-fifths of that capacity was built at utility scale. A decade ago such numbers belonged to forecasts; today they describe cranes, shipping containers of cells and substations being built beside solar farms on almost every continent.

B. Batteries do several distinct jobs, and it helps to separate them. The best known is shifting energy across the day: a four-hour installation charges through the solar-rich afternoon and discharges into the evening peak, moving midday sunshine into the hours when it is most needed. A second job is faster still. Because batteries can change their output almost instantly, they provide frequency response and other grid services that require corrections measured in seconds rather than hours — tasks a slow steam plant cannot perform. A third is to soak up power that would otherwise be wasted: when renewables generate more than the grid can carry, operators sometimes deliberately turn the supply down, a practice called curtailment; a battery with spare capacity can store that electricity instead. Finally, a charged battery held ready before a predictable evening peak can act as a reserve, reducing dependence on generators that run only for a few expensive hours each year. It is this versatility — fast, silent, and dispatchable on command — that makes a single device useful in several jobs at once, a flexibility no traditional power station can match.

C. The numbers on the ground show how quickly this is happening. In the United States, utility-scale battery capacity reached roughly 43.6 gigawatts at the end of 2025 and climbed to nearly 52 gigawatts by mid-2026 after a further eight gigawatts were added in the first six months alone. Operators reported plans for many more gigawatts over the following two and a half years, although such announced projects do not always enter service on schedule. The pattern is global. In its net-zero scenario, the International Energy Agency estimates that worldwide storage capacity must rise to around 1500 gigawatts by 2030 if electricity systems are to absorb the planned flood of wind and solar. Lithium iron phosphate batteries, a cheaper and safer chemistry that avoids problematic cobalt, accounted for roughly ninety percent of recent installations. Costs, meanwhile, continue to fall: project prices dropped by about forty percent in 2024, to around 150 dollars per kilowatt-hour. This steep decline is the single reason storage has gone from experimental to mainstream so quickly: each year of production experience made the next year's installations easier to justify financially.

D. Yet batteries have a definite horizon, and engineers are careful not to pretend otherwise. The batteries being built today are superb at balancing the grid over hours, not over days. A four-hour installation smooths the daily rise and fall of solar beautifully, but it is useless against a stretch of cloudy, windless weather lasting several days, or against the slow seasonal shift from summer sun to winter demand. As the required duration grows, lithium-ion storage becomes disproportionately expensive, because holding more energy means buying more cells. For these longer needs, engineers point to a different toolkit: pumping water uphill to release it later, compressing air, storing heat, and newer electrochemical designs that pass liquid electrolytes through external tanks. The United States Department of Energy defines long-duration storage as systems able to deliver power for ten hours or more, and it funds exactly these alternatives because ordinary batteries cannot stretch that far economically. The contrast is not a failure of batteries but a reminder that a tool designed for minutes is being asked to do a job built for days. Pumped hydro, which moves water uphill and lets it fall through turbines, already does this at huge scale, but it requires the right valleys and a great deal of concrete.

E. This is why describing batteries as the "missing piece" can mislead if it implies they are the whole solution. A battery can only charge from renewables it can physically reach, so reinforced transmission lines and new substations remain essential; storage may ease local congestion but cannot replace every upgrade to the wires. Nor is storing every spare kilowatt-hour always the cheapest route. Shifting demand itself — charging electric vehicles through the sunny afternoon, scheduling industrial loads to cheap midday hours — can absorb surplus power more directly than any battery. The best storage projects, experienced utilities say, begin with a specific grid problem rather than a favourite chemistry: define the task, decide how many hours the system must run, and then compare batteries against transmission, flexible demand and long-duration alternatives. On that view, grid-scale storage is genuinely a missing piece, but only one among several. It excels at short, repeated, fast-response balancing; for longer gaps and seasonal swings, a broader portfolio is the honest answer. The missing piece, in the end, is not a device but the willingness to design a grid that expects variability rather than one that simply tries to power through it.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. The several jobs a grid battery performs ii. How battery costs are calculated by manufacturers iii. The rapid build-out visible in the data iv. Why even batteries have their limits v. Why transmission lines are obsolete vi. The balanced, honest conclusion vii. The history of lithium-ion chemistry

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. Why do batteries matter as wind and solar grow? A. They burn fuel more cleanly than coal. B. They store energy when supply is abundant and release it when demand peaks. C. They replace the need to generate any electricity. D. They make weather forecasts unnecessary.

6. What is curtailment? A. The recycling of old batteries. B. Deliberately reducing renewable output when the grid cannot use it. C. A type of long-duration battery. D. The inspection of transmission lines.

7. Why are lithium-ion batteries unsuitable for multi-day shortfalls? A. They cannot be switched on quickly. B. Storing energy for longer periods becomes disproportionately expensive. C. They produce too much noise. D. They only work at night.

8. What does the writer recommend before choosing storage? A. Buying the largest battery available. B. Starting with a clear grid problem and comparing alternatives. C. Waiting until all fossil fuels are gone. D. Choosing the cheapest cell regardless of need.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. About 108 gigawatts of new battery storage were installed worldwide in 2025.
10. Lithium iron phosphate batteries use large amounts of cobalt.
11. A four-hour battery is well suited to a week-long period of no wind or sun.
12. The net-zero scenario requires around 1500 gigawatts of storage by 2030.
13. Battery projects in the United States are all guaranteed to enter service on schedule.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

Batteries can shift midday (14) _____________ into the evening peak and also provide fast (15) _____________ response measured in seconds.

Answers & Explanations

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