The June 2025 heat dome pushed CAISO real-time wholesale electricity prices to $1,000 per MWh — 10x the typical summer-peak price. Variable-rate residential customers in California saw June bills 32 percent above May. Locked-rate customers paid their signed rate through the entire event. Heat-dome events are forecast 7 to 14 days in advance.
The June 2025 heat dome
High-pressure system stalled over the southwestern US from June 24 to July 5, 2025. Phoenix hit 119F, Las Vegas 118F, Sacramento 112F.
CAISO wholesale prices hit $1,000/MWh during the peak demand window June 28. Variable-rate residential customers in California saw bills 32 percent above May.
Pre-cooling and load-shifting during forecasts
Households on TOU plans can pre-cool to 72F by 4 pm and ride deadband through 9 pm. Cuts AC kWh during peak window by 35 to 50 percent.
Battery-buffered homes can self-consume during the peak window, fully insulating from wholesale spikes. The microgrid model becomes attractive in heat-dome-prone regions.
Lock the rate before the next reset.
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Quick answers from the editorial desk
How does a heat dome form?
Utility rate cap protections?
TOU during heat dome?
Battery-buffered home advantage?
Further reading