India is adding solar and wind capacity at a pace that would have seemed impossible a decade ago. In FY 2024-25, India added a record 29.52 GW of renewable energy, taking total installed renewable capacity to 220 GW. Solar crossed 100 GW. Wind crossed 50 GW. Renewables now make up over 50% of India's total installed power capacity — a COP26 commitment achieved five years ahead of schedule.
That's genuinely impressive. But here's the thing nobody is talking about loudly enough.
As India keeps piling on solar and wind, a new problem is quietly building up in the background. Not the hourly intermittency problem everyone already knows. Something bigger. Something seasonal.
What we already solved (sort of)
When India first started adding large-scale solar and wind in the early 2010s, the tenders were what the industry calls "vanilla." Just generation. No storage attached.
Grid operators had to deal with the consequences. A cloud rolls over a solar park in Rajasthan. Wind suddenly drops in Gujarat. Frequency dips. Ancillary services scramble. Grid operators reach for backup. It worked, but it was messy, expensive, and stressful for everyone managing grid stability in real time.
Co-located battery storage changed that. The share of hybrid tendered capacity (renewables plus storage) jumped from about 12% in 2021 to over 49% in 2024. The Ministry of Power has now mandated that all future solar tenders include a minimum two-hour co-located energy storage system equivalent to 10% of installed solar capacity.
This is a big deal. It means renewable developers now sign power purchase agreements and actually dispatch uninterrupted power, whether to a DISCOM or a corporate buyer. The battery handles the gaps. Cloud cover at noon? The battery fills in. Wind dies for two hours? Battery covers it.
Intra-day intermittency, largely handled. Problem solved at the hourly scale.
But now zoom out. Way out.
The seasonal problem is coming for us
India's renewable energy is seasonal in nature. Wind in Gujarat and Tamil Nadu peaks dramatically during the monsoon. Solar capacity factors climb during summer months when irradiation is high and cloud cover is minimal. As India adds more of both, there will be specific months in the year when the grid is drowning in cheap, clean electricity — and other months when it runs short.
This is not a future hypothesis. It is already visible in curtailment data. As capacity grows, curtailments during high-renewable months will increase. Zero-cost electricity simply gets wasted because there is nowhere to put it.
Now think about demand. Can it shift to absorb this?
DISCOMs have tried. Seasonal tariffs — lower prices during high-RE months to pull consumption forward — have been on the table for a while. But demand has stayed stubbornly inelastic. Factories don't easily switch production schedules. Households don't move their peak consumption because electricity is 10% cheaper in July. The price signal has not been strong enough, or consistent enough, to move the needle.
The demand side alone won't save us. The supply side needs to find a way to store energy not for hours, but for weeks and months.
The OG battery from ancient times
This is where pumped storage projects (PSPs) become interesting. The concept is elegantly simple. Think of it as using electricity to move water uphill, then letting gravity bring it back down when you need power again.
During months when solar and wind are producing more than the grid can absorb, that surplus electricity pumps water from a lower reservoir up to an elevated one. When the lean season arrives — with fewer sunny hours and calmer winds — the water is released back downstream through turbines, generating electricity purely from gravity. No fuel. No emissions. Just physics.
Pumped hydro storage can store vast amounts of energy for long durations, often 11 hours or more, making it ideal for meeting daily or weekly demand cycles. Once commissioned, a pumped storage project can operate reliably for 70 to 100 years, compared to roughly 15 years for a typical battery energy storage system.
India's Central Electricity Authority has estimated on-river pumped storage potential at about 103 GW, with about 44.5 GW of projects at various stages of development. The CEA has also put forward a roadmap to unlock 100 GW of pumped storage capacity by 2047, identifying over 120 potential sites with a total estimated potential exceeding 180 GW.
But here's the honest limitation. A reservoir can hold enough water to release power for days, maybe a week or two. It is not a seasonal battery. The water eventually runs out. You'd need truly massive reservoir infrastructure to bridge a two-month deficit in wind generation. We're not there yet.
This article is just an introduction to pumped storage. There is a lot more to say about how India can unlock this potential — and that deserves its own conversation.
Do we have a solution?
Right now, truthfully, nothing does it at scale. Long-duration energy storage technologies that can bridge weeks to months of seasonal mismatch are still largely in early stages globally. Flow batteries, green hydrogen, compressed air storage, gravity-based systems — they exist in pilots and laboratories, but they are not yet deployed at the gigawatt scale that India will need.
But here is the thing. India's grid in 2050 will look radically different from today. With peak electricity demand projected to nearly double to over 450 GW by 2047, experts have argued that without large-scale long-duration storage, India's clean energy transition risks becoming grid-constrained and cost-inefficient.
Climate extremes are making this more urgent, not less. Summers are hotter, pushing cooling demand to new highs exactly when solar is at peak output. Winters are sharper and more erratic. Monsoon wind patterns are intensifying. The seasonal mismatches will grow wider, not narrower, as the climate shifts.
Planning a 30-year energy system means thinking about storage technologies that do not yet exist commercially. That is not pessimism. It is just honest long-term planning. The investment in R&D, the policy frameworks, the land and water rights for pumped hydro — all of this needs to start now, even if the technology matures over the next decade.
India solved hourly intermittency with batteries. It is now starting to address daily storage with co-located BESS and pumped hydro. The next frontier is seasonal storage — and it is the hardest problem in clean energy. It deserves to move to the centre of the conversation.
Because the sun and wind don't take a day off. But they do take a season. And we need to be ready for that.
Sources
- Ministry of New and Renewable Energy (MNRE) — FY 2024-25 RE Capacity Report
- IEEFA — India's Battery Storage Boom: Getting the Execution Right
- Mercom India — Government Mandates Two-Hour Energy Storage in Solar Tenders
- Down To Earth — India Leans on Pumped Hydro for Energy Storage
- Down To Earth — India Charts Roadmap to Tap 100 GW of Pumped Storage
- TERI — Pumped Storage Plants: Essential for India's Energy Transition
- JMK Research — India Adds Record 34.4 GW Solar and Wind in H1 2025