Why Cost Per kWh Is The Wrong Way To Price Grid Batteries

Vanadium flow batteries store energy in liquid electrolyte that doesn’t degrade with use. (Photo by Costfoto/NurPhoto via Getty Images)

NurPhoto via Getty Images

The energy storage industry prices batteries the way a car dealer sells sedans: by sticker cost. Cost per kilowatt hour. The number is clean, comparable, and increasingly cheap. BloombergNEF data shows global four-hour storage benchmarks fell 27% year on year in 2025, to $78 per megawatt hour. Lithium-ion dominates on that number. But every evening at 6 p.m. in Mumbai, Chennai, and Delhi, a grid problem plays out that the sticker price cannot explain.

India’s solar generation collapses at dusk. Coal plants scramble to ramp back online within minutes. The voltage swings cost the economy an estimated two percent of GDP annually, and the batteries designed to smooth them face a duty cycle that most lithium warranties cannot survive. Invinity Energy Systems, a London-listed vanadium flow battery manufacturer backed by the UK’s National Wealth Fund, is positioning a different technology against that specific problem. Its CEO, Jonathan Marren, argues the industry is using the wrong math.

“At the moment people quote on a cost per kilowatt hour basis,” Marren told me. “But a cost per kilowatt hour doesn’t really get to what battery you’ve got.”

Three structural gaps explain why.

The Cycle Trap

Lithium-ion costs have collapsed because of manufacturing overcapacity and slowing EV demand, not because grid storage economics improved. When Indian grid operators need four or five charge-discharge cycles daily to manage the solar-to-coal handoff, lithium’s warranty constraints become the binding variable, not its headline price.

Marren frames it in asset terms: “If you cycle four times a day, that’s a very valuable asset. If you’re only going to cycle once a day or two or three times a week, suddenly your high cost per kilowatt hour isn’t getting to the heart of that use case.”

Vanadium flow batteries store energy in liquid electrolyte that circulates through a stack, rather than plating ions into solid cells. The chemistry doesn’t degrade with use. Invinity’s Endurium system is designed to deliver over 242,000 megawatt hours of throughput across a 30-year life, compared with roughly 68,500 megawatt hours from a lithium system under the same heavy-cycling conditions. The difference is the gap between the sticker and the receipt.

“Please use it as often as you can,” Marren says, “because it’s like any asset. The more you use it, the better.”

The Fire Underground

In Laufenburg, Switzerland, a company called FlexBase is excavating deep beneath a planned AI data center to install a 1.6-gigawatt-hour vanadium flow battery. The project sits at a grid junction where Swiss, German, and French transmission networks meet, and its logic inverts the conventional duration argument. FlexBase is deploying a two-hour flow battery, not because it needs long duration, but because it needs relentless cycling without fire risk.

“You’re not going to put a lithium battery beneath a data centre in the ground,” Marren says. “Some may think that project is a little bit challenging, but they’ve been in the ground for the last year and have already reached 25 metres down.”

For data center operators chasing 99.9999% uptime, the siting constraint matters as much as the price tag. Thermal runaway risk in lithium systems drove NFPA 855’s 2026 edition to mandate hazard mitigation analysis for all battery installations regardless of size. Swiss Re expects data center insurance premiums to more than double to $24.2 billion by 2030. A non-flammable chemistry that sits safely under the server hall changes the insurance calculation, the permitting timeline, and the building’s footprint. None of that shows up in cost per kilowatt hour.

The Supply Chain That Lights Up Eyes

Invinity entered India in September 2025 through a partnership with Atri Energy Transition, including plans to establish domestic manufacturing. The timing was deliberate. India tendered 102 gigawatt hours of energy storage in 2025 alone, nearly equal to the cumulative total from 2018 to 2024. Only 0.7 gigawatt hours was actually operational by year-end. The gap between ambition and execution defined the opportunity.

When Marren told Indian officials the company could source close to 100% of subcomponents domestically rather than assembling Chinese-manufactured cells, “you could see their eyes light up, because they were like, ah, this is now really attractive to me.”

The reaction reflects a structural tension. India’s December 2025 mandate requiring 20% domestic content for battery projects under its viability gap funding scheme puts pressure on lithium suppliers whose cell supply chains run through China. Flow batteries are built from steel containers, plastic tanks, pumps, and industrial wiring. Indian factories already make those things.

India isn’t the only node. Invinity sources balance-of-system components from China, manufactures core electronics in the UK and Canada, signed a licensing agreement with China’s UESNT targeting 1.9 gigawatt hours of production by 2030, and appointed a new VP for U.S. business development in February 2026 with a U.S. manufacturing facility planned for later this year. “There is a huge advantage for our business to have multiple supply chains from emerging markets,” Marren says. “In a complex geopolitical situation, you always have a route around the world.”

The Metric That Catches Up

The shift away from cost per kilowatt hour is gathering institutional weight. An LDES Council and EPRI benchmarking study published in January 2026 found that assumptions built for short-duration storage don’t capture the cost characteristics of longer-duration technologies. In April, the LDES Council released a policy whitepaper specifically on India, noting that solar curtailment alone has cost Indian power producers over $26 million in lost revenue since April 2025. India’s state-run NTPC issued a tender in February 2026 for a 100-megawatt-hour vanadium flow battery at Khavda Solar Park in Gujarat. In China, Rongke Power connected the world’s first gigawatt-hour-scale flow battery in Xinjiang in January. The technology’s bankability argument just gained a three-comma proof point.

Marren draws a sharper line on who his customer actually is: “Those who understand that they are building an asset for 30 years get this. If you are a developer looking to merely trade on the grid, buy low, sell high just once or twice a day, it’s not the right type of person to be talking to.”

India’s 411-gigawatt-hour storage target by 2032 will be filled by multiple technologies. Lithium will capture the use cases that suit its economics. But the procurement officers running tenders across Gujarat, Maharashtra, and Rajasthan face a question their spreadsheets aren’t built to answer: what does a battery cost on cycle ten thousand?