An emergency SMS text alert may have prevented a blackout in California. Officials say the plea resulted in an “immediate and significant drop” that reduced potentially unmanageable demand on the energy grid.

The message went out from the California Independent System Operator, which oversees power supplies in the state. It puts out a “Flex Alert” when there’s a high level of demand. That’s most common in the late afternoon and evening on particularly hot days, at which point use of air conditioning rises but input from solar is dropping.

The Flex Alert asks consumers to set thermostats (for air conditioning) to 78 Fahrenheit, turn of any unnecessary lights, and avoid using appliances such as electric ovens and dishwashers where possible. It’s an entirely voluntary process.

While such alerts aren’t uncommon, they are usually limited to the organization’s website and social media. The difference this week was that, with the risk particularly high thanks to an extended heatwave, officials decided to declare an Energy Emergency Alert that makes the same request to consumers (though suggests turning off all non-essential power), but goes out to all users in affected areas via text message.

The idea appears to be to have a balance between getting some reduction in demand for “ordinary” shortfalls, but saving the text alerts for the most serious cases to avoid a “boy who cried wolf” effect.