Every house is already a battery, with significant thermal mass. Unfortunately, this means that the is not real-time but forward-looking: The thermostat needs t

Every house is already a battery, with significant thermal mass. Unfortunately, this means that the is not real-time but forward-looking: The thermostat needs to predict when load and price will peak a few hours early, and turn the AC on before that happens. If you cool the house down lower than necessary in the morning, it will warm up through a high-load afternoon, but stay comfortable, spreading the load and reducing usage during that price peak. Of course, if everyone does this on every morning when the national weather service predicts high temperatures, you've just moved the demand forward a few hours and not actually spread it out.