There is a number in the energy world that does not get the attention it deserves: renewables are about to become the world’s biggest source of electricity. Not the biggest growth story, not the biggest investment theme — the biggest source, full stop. The International Energy Agency now expects that to happen by 2026 at the latest, with solar and wind climbing past coal for the first time in a century.
That is a genuinely historic milestone. It is also, in a quiet way, the beginning of a harder problem than the one we just solved.
The milestone, in plain numbers
Let me give you the scale. In 2025, the world added a record amount of new solar and wind capacity — roughly 814 gigawatts, 17 percent more than the year before. Total wind and solar capacity has now passed four terawatts. To put that in context, a single gigawatt can power a few hundred thousand homes; four terawatts is thousands of times that.
And the mix is striking. For every gigawatt of new wind, the world is adding nearly four gigawatts of solar. Solar has become the workhorse — cheap, modular, deployable almost anywhere. In the United States, wind and utility-scale solar together hit 17 percent of electricity generation in 2025, and utility-scale solar output jumped 34 percent in a single year.
The trend is even more dramatic in fast-growing economies. India installed a record amount of new solar and wind in the first half of 2026 alone, driven partly by a rooftop-solar boom. China and India together are expected to account for the largest share of global electricity-demand growth, and both are building renewable capacity at a pace that would have seemed impossible a decade ago.
Why the milestone matters
Coal has been the backbone of global electricity for over a hundred years. It powered the industrial revolutions, powered the 20th century, and it still provides around a third of the world’s power. When a source with that kind of dominance gets overtaken, it is not a technical footnote. It is a signal that the economics have shifted permanently.
Renewables are not winning because of subsidies alone. They are winning because, in most of the world, building a new solar farm is now cheaper than running an existing coal plant. The fuel is free, the maintenance is light, and the technology keeps getting better. Once that cost gap opens, it does not close again.
The environmental side is real too. Global electricity demand is growing fast — driven by factories, electric vehicles, air conditioning and data centers — and the IEA expects emissions from power generation to roughly plateau this decade as renewables and nuclear expand. That is the first time in a long time that growth and emissions have been able to decouple at this scale.
The harder problem starts now
Here is where I want to be honest about the hard part. Making lots of clean electricity was never the real challenge. The challenge is that the grid was built for a different kind of generation.
Coal and gas plants can be switched on and off on demand. The sun and wind cannot. So as renewables take a bigger share, the system needs new tools: energy storage to smooth the gaps, flexible demand that can shift when it uses power, and a grid that can move electricity from windy and sunny regions to where people actually live.
The numbers show the gap. Even with record additions, a meaningful share of wind and solar in some regions is being curtailed — generated but wasted because the grid cannot absorb it at that moment. Storage is growing fast, but it is starting from a small base. Battery capacity is doubling every couple of years, which is impressive and still not enough.
Then there is the aging infrastructure itself. Transmission lines, substations and transformers were designed decades ago, and in many countries they are bottlenecks. You can build the cheapest solar farm in the world, but if there is no line to carry its power, it is just a field of expensive panels. Grid investment is finally climbing, but it is chasing a moving target.
Storage is the quiet hero nobody talks about
If there is one technology that decides how far the renewable transition goes, it is energy storage. Renewables are abundant when the sun shines and the wind blows; the whole problem is the hours in between. Storage is what bridges them.
Battery costs have fallen far enough that grid-scale storage is now being built at serious scale, not as a pilot but as a standard part of new projects. In the United States, project developers are preparing a record amount of new utility-scale capacity, and an unusually large share of it is battery storage attached to solar farms. The pairing is logical: charge during the cheap midday sun, discharge during the evening peak.
But even this growth is running behind where it needs to be. The IEA and other bodies keep saying the same thing in different ways: storage needs to grow several times faster than it currently is to keep the grid reliable as the renewable share climbs. It is growing fast — doubling every couple of years — and it is still not enough. That is the honest measure of how big the task is.
There are also longer-duration options being developed — pumped hydro, compressed air, and a range of experimental chemistries that aim to store power for days rather than hours. None of them is ready to replace batteries at scale, but the fact that the industry is actively hunting for them tells you where the bottleneck really is. The fuel is free; the problem is holding onto it.
Flexible demand: the least glamorous solution
There is another piece of the answer that rarely makes headlines, because it is about behavior rather than hardware: making electricity demand flexible. If appliances, factories and even electric vehicle chargers can shift their consumption to times when power is cheap and abundant, the whole system needs less storage and less new capacity.
This is already happening in places with smart pricing. Households with time-of-use rates learn quickly to run the washing machine at midday and charge the car overnight. Large industrial users sign contracts that let the grid shut them down for a few minutes in exchange for lower rates. These arrangements are unglamorous, but they are among the cheapest ways to keep a high-renewable grid stable.
The catch is that flexibility does not distribute itself fairly. Households that cannot shift their usage — the elderly, the poor, people with inflexible work schedules — end up paying peak prices they cannot avoid. So the policy question is not just how to build flexibility, but how to build it without making the transition another way the well-off pull ahead. Every country is figuring this out on the fly.
What this means for ordinary people
The milestone matters for more than just engineers and utilities. Electricity prices are increasingly shaped by how well the grid handles variability, not just by the cost of fuel. In places with lots of cheap solar, daytime power can get genuinely cheap — sometimes even negative — while evening peaks stay expensive. How you shift your usage can start to show up on your bill.
It also reshapes who pays for the transition. Storage, transmission and grid upgrades have to be funded somehow, and that cost eventually lands in rates. Whether it lands fairly — on those who can shift their demand, versus those who cannot — is a policy question every country is still working out.
None of this is an argument against renewables. It is the opposite: it is what success looks like. The milestone is real, and it is worth pausing on. But the next phase is not about building more turbines. It is about building the invisible plumbing that lets the electricity actually reach us.
The part nobody celebrates — transmission lines, batteries, flexible pricing — is exactly the part that decides whether this historic milestone turns into a reliable system, or a headline.