US renewable curtailment shatters records in 2026 as transmission fails to keep up
CAISO and other ISOs throw away record solar and wind and hit deepening negative prices, with bottlenecks, not oversupply, the culprit
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Summary
US Renewables curtailment is breaking records again in 2026. Four of seven US ISOs set annual curtailment records in 2024; 2025 broke them and the trend is accelerating, with CAISO solar and wind curtailment spiking to record levels across April 2026. CAISO threw away 3.4 million MWh in 2024 (+29% YoY). Negative-price hours are surging as utility-scale and behind-the-meter solar flood midday while load is weak, prices often go negative around noon as batteries charge. Analysts pin the cause on Transmission bottlenecks, not generation oversupply: congestion drives curtailment and negative prices simultaneously. The same dynamic appears across Europe.
By the numbers
- 4 of 7, US ISOs that set curtailment records in 2024 (broken again since).
- 3.4 million MWh, CAISO solar+wind curtailed in 2024 (+29% YoY).
- April 2026, record-level curtailment spike across CAISO.
- Surging, count of negative-price hours coinciding with peak solar.
Why it matters
Curtailment and negative prices erode the value of new renewables and the returns that finance them , a self-limiting drag unless storage and transmission catch up. It is the clearest market signal that the US grid's bottleneck is wires, not panels.
What to watch
- Whether 2026 sets fresh annual curtailment records across ISOs.
- How fast storage absorbs midday surplus and lifts midday prices.
- Transmission and interconnection reform pace.