Is it cheaper to run AC all day or turn it off?

Is it cheaper to run AC all day or turn it off depends on climate, insulation, AC efficiency, and how long you are away, but generally it is cheaper to turn up thermostat when away rather than turning completely off for short periods, and turning off for long periods saves more. If you leave house for few hours, leaving AC on at higher temperature like 78F instead of 72F uses less energy than turning off and letting house heat up to 90F then requiring AC to work hard to cool back down, because AC must remove accumulated heat from walls and furniture. For well-insulated home, temperature rises slowly, so turning off for 8 hours while at work saves energy because AC not running at all, even though it must run longer to cool back down, net savings exist because heat gain is less when indoor temp higher. Studies show turning off or setting back 7 to 10 degrees for 8 hours saves up to 10% on cooling costs. Inverter AC with variable speed is more efficient to leave running at higher setpoint than old single speed that cycles. So best strategy is use programmable thermostat to set higher temp when away and lower when home, rather than running all day at same low temp or turning off completely then blasting.