Summary
Grids are built for the few hours a year when demand peaks. The rest of the time there is room on them. In February 2025, researchers at Duke University's Nicholas Institute measured that room for the United States: 76 GW of new load could connect to existing grids if it accepted curtailment in 0.25% of its hours, rising to 126 GW at 1%.
We applied the same method, step for step, to nine years of hourly load in 18 European markets. With 1% of its energy curtailed, about 71 GW of new load fits on Europe's existing grids. That is 14% of their combined peak.
The curtailment is short and shallow. At 1%, a new load would see about 408 hours a year with some restriction, in events averaging 4.6 hours. In 91% of those hours the grid still carries more than half of it.
Regulators are now writing the contracts to use this room. Flexible connection agreements are in EU law, in force in Germany and the Netherlands, and offered by most distribution networks in Great Britain.
Europe against the United States
New load that fits on existing grids, by curtailment limit
Europe, 18 markets, against Duke's United States result
- Europe, 18 markets
- United States, 22 balancing areas (Duke)
Europe's numbers are lower than the US ones for two reasons. The 18 markets have a combined peak of about 508 GW, against 744 GW for the US systems Duke studied. European demand also fell over the period, so the peaks that set the thresholds come from earlier years. France's winter threshold dates from February 2018 and Great Britain's from January 2017.
France, Germany and Great Britain lead
New load at 1% curtailment, ten largest markets
GW that fits on each country's existing grid
France has the most room, 16.9 GW at 1%. Its load is strongly winter-peaking, so the summer months leave a large margin. Germany follows with 9.5 GW and Great Britain with 8.7 GW. Great Britain's figure is likely understated: the national demand series we use leaves out some station load, pumping and exports.
| Market | Peak load, GW | New load at 1%, GW | Share of peak |
|---|---|---|---|
| France | 94.5 | 16.9 | 18% |
| Germany | 81.3 | 9.5 | 12% |
| Great Britain | 49.8 | 8.7 | 17% |
| Italy | 53.8 | 6.4 | 12% |
| Spain | 41.8 | 5.3 | 13% |
| 13 other markets | 187.0 | 24.6 | 13% |
| All 18 markets | 508 | 71.4 | 14% |
What the curtailment looks like
A flexible connection does not mean a load switching off for weeks. At 1% curtailment, the average European market restricts a new load for about 408 hours a year, mostly in the shoulder months and on winter evenings. Events last 4.6 hours on average. In 91% of the restricted hours the grid still delivers more than half of the connection.
In France at 1%, a third of the curtailed energy falls in April and another 15% in October, when demand is still above the summer threshold. In Great Britain, 40% falls in January.
That shape matters. Short, partial restrictions are what an on-site battery is built for. A battery sized to a few hours of the shortfall, not to the whole load, can turn a flexible connection into power the site experiences as firm.
Flexible connections are moving into law, in Europe and the US
The method assumes a new load accepts curtailment. Until recently, few connection contracts allowed that. That is changing on both sides of the Atlantic:
- European Union. The 2024 reform of electricity market design added flexible connection agreements to EU law (Directive (EU) 2024/1711, new Article 6a of Directive (EU) 2019/944). Member states must set a framework for network operators to offer them where capacity is limited.
- Germany. §17(2b) of the Energy Industry Act (EnWG) allows grid operators to agree flexible connections that limit import or export at times of congestion.
- Netherlands. With large parts of the grid congested, operators offer non-firm transport rights, so customers can connect now in exchange for restrictions at peak times.
- Great Britain. Four of the six distribution network operators already issue non-firm demand connections with contractual curtailment limits, and the regulator is weighing curtailment terms for data centres.
- United States. In Texas, ERCOT's Batch Zero process (approved by the regulator in June 2026) studies loads of 75 MW and above together and lets a campus connect for more than the grid can guarantee: it either brings its own power, or agrees to automatic curtailment above a guaranteed share. The Texas regulator has also approved large campuses on condition that they can cut load or switch to backup within 30 minutes of a grid call. In PJM, analysis by Camus, encoord and Princeton found that making 20% of a 1 GW data centre flexible saves other customers about $78m a year.
- Ireland. New data centres of 10 MVA and above must bring dispatchable capacity that can support the system.
Method
We replicated the method of the Duke study as published. For each market we take hourly actual load for the nine most recent full years, 2017–2025, from ENTSO-E data (via energy-charts and Open Power System Data) and, for Great Britain, from NESO. Each market gets two thresholds, one for the summer half of the year and one for winter. A new constant load L is curtailed in any hour where existing demand plus L exceeds the threshold. Its curtailment rate is curtailed energy divided by L × 8,760 hours, averaged over the nine years. We then find the largest L that keeps the rate at or below each limit.
One adaptation: Duke sets the summer threshold from the June–August peak and the winter one from the December–February peak. Many European systems peak outside those months, which would give zero headroom for Great Britain and Germany. We take each threshold as the highest load over all the months it governs (April–October, November–March). That matches Duke wherever the peak falls in the core months and is never below Duke's threshold. Results are at country level.
Source for the US figures: Tyler H. Norris, Tim Profeta, Dalia Patino-Echeverri and Adam Cowie-Haskell, Rethinking Load Growth: Assessing the Potential for Integration of Large Flexible Loads in US Power Systems, Nicholas Institute for Energy, Environment & Sustainability, Duke University, February 2025.