Curtailment is a price signal that nobody is allowed to receive

Victoria Shinder21 September 2026, 09:303 min read

Two numbers from this week's reporting, from opposite ends of the world.

On Sunday, Australia's National Electricity Market curtailed 11,109 MW of available renewable output — a record — on the same weekend it set a record for renewable share. And in Brazil, module imports for utility-scale projects in the first half of 2026 fell 82%, from 2.3 GW to 430 MW, with the analyst who compiled the figures naming curtailment as the dominant cause.

These are the same event at two different points on its timeline. Australia is experiencing it. Brazil is paying for it.

What curtailment actually communicates

When a network spills output it cannot accept, it is saying something precise: at this location, at this hour, another megawatt is worth nothing. That is not a fault. It is information — arguably the single most useful piece of information a grid produces, because it identifies exactly where and when the system is full.

The problem is that in most markets the signal is delivered to the wrong party, in the wrong units, at the wrong time.

To the wrong party. The generator being curtailed is usually not the one who could act on it. It cannot build a line, move a substation, or site a data centre. The parties who could — network companies, planners, large flexible loads — often see the curtailment figure only as an annual percentage in someone else's report.

In the wrong units. "Eight percent of output was spilled" is an accounting statement. The actionable form is a location and an hour: this node, between 10am and 2pm, in spring. That is a specification for a battery, an electrolyser, a smelter shift, or a connection queue rule — and it is almost never published in that shape.

At the wrong time. By the time a curtailment number is confirmed and reported, the investment decisions it should have informed were made two years earlier on a forecast.

The feedback loop nobody designed

So the signal goes where it can go, which is into the developer's discount rate. Curtailed revenue is uncertain revenue; uncertain revenue is priced as risk; risk raises the cost of capital; and capital cost, as Slovenia's own reactor economics showed this week — €65/MWh at 2% and €103/MWh at 4% — is the dominant term in the price of anything capital-heavy.

That is how a physical constraint at midday in one region becomes, eighteen months later, a collapse in module orders on another continent. Nobody chose it. It is what happens when the only channel available for the information is the one that prices fear.

What would actually route it

Locational signals, in whatever form a market can bear. Nodal pricing is the purest version and the most politically expensive; zonal refinements, connection charges that vary by node, and time-of-use export tariffs all carry part of the same message.

Flexible load with a reason to sit where the surplus is. Australia spilled 8.4 GW at the exact moment 4.46 GW was going into batteries. The gap is not a technology problem — it is a siting and incentive problem, and it is the one large consumers are best placed to solve for themselves.

And publishing curtailment where developers look before they commit. Half-hourly, by node, with history. A developer who can see that a node has spilled 12% of available output for three consecutive springs will not build there, and will not have to discover it after financial close. That is cheaper for everyone than the alternative, which is paying for the information through the cost of capital for a decade.

Curtailment is not a symptom of too much renewable generation. It is the grid telling the truth about where it is full, into a system with no wire connecting that truth to the people who could act on it.