The central air conditioning system is one of the biggest consumers of electricity in a house. When the AC goes into active cooling mode and powers the compressor, it can use on average 3,500 watts per hour. The only appliance that might use more is an electric water heater.
Because AC’s can take up such a significant chunk of your electrical budget during a hot So. Cal summer, it makes sense to limit how much you have it running. This is why we recommend keeping the thermostat at around 78°F during the day: it’s a comfortable temperature that won’t force the air conditioner to run too long.
What about when you’re away from home? It sounds like it makes sense to just turn the AC off so it won’t use any power. The situation isn’t so simple, however. Unless you plan to be away from home for several weeks, we advise you to keep the air conditioner on—but not necessarily at the same settings.