Why Can’t We Just Build More Solar Power?

Last updated: 2026-10-24

Building more solar and wind capacity isn’t the hard part – building the transmission lines, storage and grid flexibility to actually use all of it is. When supply outruns the grid’s ability to move or absorb it, operators curtail: they switch generators off or dial them down. India’s grid curtailed solar and wind capacity totaling 118.6 GW at some point during September 2026 alone, according to JMK Research – a vivid, current example of a structural problem showing up in fast-growing renewable markets worldwide.

What Is Curtailment, Exactly?

Curtailment is the deliberate reduction of a generator’s output below what it could otherwise produce. For wind and solar, grid operators typically order it for one of three reasons: oversupply (more generation than demand at that moment), transmission congestion (the power is there, but the wires to move it aren’t), or market economics (producers curtailing to avoid selling into negative prices). NREL and other grid researchers note that as wind and solar grow as a share of generation, some curtailment becomes a normal, even economically rational, feature of the system – not automatically a sign something has gone wrong. The debate is over how much curtailment is an acceptable cost of cheap renewables versus a sign that grid investment is lagging behind.

Case Study: India’s September 2026 Curtailment Data

JMK Research’s monthly tracking separates two measures that are often conflated in coverage of India’s renewables sector: energy actually lost, and capacity merely exposed to a curtailment event at some point in the month.

JMK Research notes September’s improvement over August and summer 2026 reflects a seasonal lull (cooler weather, lower output) rather than a structural fix to the underlying transmission bottleneck.

JMK Research attributes the curtailment to a mix of demand-generation mismatches, transmission constraints, and limited storage and grid flexibility – with transmission singled out as the binding constraint on further renewable build-out, not oversupply alone. (See TDE’s news coverage: India’s Grid Curtailed 118.6 GW of Solar and Wind Capacity in September.)

Not Just India: California and Australia

The same dynamic shows up in mature, high-penetration grids. The U.S. EIA reported that California’s grid operator, CAISO, curtailed about 1.5 million MWh of utility-scale solar in 2020 – roughly 5% of total solar production that year – largely because midday solar output arrives when demand, and the ability of other plants to ramp down, is limited. Australian grid modelling cited by industry press has found wind and solar facing as much as 20% curtailment in a grid carrying a very high share of renewables, with the market operator AEMO concluding that adding more storage to absorb the surplus is not always economically efficient once generation is already abundant at that time of day.

The Fixes: Storage, Transmission, and Flexibility

Three responses recur across markets dealing with curtailment:

• Storage build-out. India’s battery storage capacity could expand nearly 50-fold by 2032, according to financial services firm Nuvama, as developers and state utilities pair storage with new renewable capacity specifically to cut curtailment losses (see TDE: India’s Battery Storage Capacity Set to Jump Nearly 50-Fold by 2032). South Africa has taken a similar approach, fast-tracking 4,600 MW of battery storage to address its own curtailment problem.
• Grid flexibility and virtual power plants. Rather than only adding new wires, grid operators are increasingly contracting demand-side flexibility. Google, for example, expanded its virtual power plant agreement with Voltus in the PJM market tenfold to more than 1 GW in October 2026 (see TDE: Google Expands Its PJM Virtual Power Plant Tenfold to Over 1 GW) – a sign that large buyers are being enlisted to shift load rather than wait for new transmission to be built.
• Transmission investment. Ember’s finding that India met only about 80% of its transmission-build targets over the past five years underscores that, in many markets, wires – not panels or turbines – are the actual bottleneck. Grid connection delays and interconnection-queue backlogs (a related, if distinct, problem covered elsewhere in TDE’s grid reporting) compound the issue.

Not every fix lands cleanly: Germany’s Sonnen, a residential battery maker, filed for insolvency in October 2026, just months after being sold by Shell – a reminder that storage-industry growth is not guaranteed even where the underlying need for storage is real (see TDE: German Battery Maker Sonnen Files for Insolvency Months After Shell Sale).

Is Curtailment Always a Problem?

Views differ. Some coverage frames curtailment as wasted clean generation and a direct economic loss to developers. Other researchers, including at NREL, argue that in a grid increasingly dominated by low-cost wind and solar, some curtailment is simply cheaper than building enough storage or transmission to capture every last megawatt-hour – a Minnesota-based academic study has found that deliberately overbuilding solar capacity and accepting some curtailment can be more cost-effective overall than trying to store or move all of it. The honest answer is that curtailment is a symptom with more than one possible diagnosis: sometimes it signals under-investment in grid infrastructure, and sometimes it reflects a grid making a reasonable economic trade-off.

Frequently Asked Questions

Why can’t we just build more solar panels?
We can, and many countries are – but solar and wind output often arrives at times of day when demand, transmission capacity, or storage can’t absorb it. Without enough grid capacity or storage to use the extra power, operators curtail (switch off) part of it rather than let it destabilize the grid.

What is curtailment in renewable energy?
Curtailment is when a grid operator deliberately reduces a wind or solar generator’s output below what it could otherwise produce, usually because of oversupply, transmission congestion, or to avoid negative electricity prices.

Why is India curtailing so much solar and wind power?
JMK Research attributes it mainly to transmission bottlenecks rather than oversupply: renewable capacity has been built faster than dedicated transmission links, with roughly a third of recently commissioned capacity still relying on temporary, non-dedicated grid connections as of May 2026 (ICRA).

Does more battery storage solve curtailment?
It helps, but it isn’t the whole answer. India’s operational battery capacity (9.1 GWh as of August 2026, CREA) remains far below its tendered pipeline (~151 GWh), and transmission investment – not storage alone – is the constraint analysts most often cite as binding.

Is curtailment always a sign of a problem?
Not necessarily. Some grid researchers, including at NREL, view a degree of curtailment as an economically reasonable feature of a grid with abundant low-cost renewables, rather than proof that something has gone wrong.

Related The Daily Energy Pages

• India’s Grid Curtailed 118.6 GW of Solar and Wind Capacity in September
• India’s Battery Storage Capacity Set to Jump Nearly 50-Fold by 2032
• Google Expands Its PJM Virtual Power Plant Tenfold to Over 1 GW
• German Battery Maker Sonnen Files for Insolvency Months After Shell Sale
• Saudi Arabia’s Renewable Energy Target: Progress Tracker

Sources

• JMK Research, monthly renewable curtailment tracking for India, September 2026
• Centre for Research on Energy and Clean Air (CREA), curtailment and battery storage analysis, 2026
• ICRA, renewable grid-connection analysis, as of May 2026
• Ember, India transmission-build target analysis, 2026
• U.S. Energy Information Administration, California (CAISO) utility-scale solar curtailment data, 2020
• AEMO-related Australian renewable curtailment reporting, via industry press, 2026
• National Renewable Energy Laboratory (NREL) research commentary on curtailment as a grid-planning feature
• Nuvama, India battery storage growth projection to 2032

Illustrative image. Photo: Shixart1985, CC BY 2.0, via Wikimedia Commons — source