During heat waves, the demand for air conditioning (AC) in buildings surges significantly, while the power system’s ability to respond to peak loads is limited. This discrepancy can lead to electricity shortages and outages during peak demand hours. To mitigate this issue, we evaluate two pre-cooling (PC) strategies for AC systems during off-peak hours to shift peak power demand and reduce the operational pressure on the power grid. Simulation results for a typical office building show the effectiveness of two PC strategies, nighttime pre-cooling (NPC) and daytime pre-cooling (DPC), in two scenarios where the AC system is turned off (AC-off) and the AC system is turned on (AC-on) during peak hours. In the AC-off scenario, both PC strategies effectively mitigated overheating, reducing peak temperatures by approximately 2.5 ℃ during a heat wave day and maintaining relatively slow temperature trends during peak hours. In the AC-on scenario, NPC reduced peak electricity consumption by 45.43%, while DPC achieved a reduction of 49.84% compared to the baseline, thereby effectively transferring peak power demand. However, the total electricity consumption for a day for both strategies in both scenarios increased by 25–30% compared to the baseline. In terms of energy cost, DPC resulted in a 5–10% increase, whereas NPC achieved a reduction of about 20% due to the lower nighttime tariff compared to the baseline. Consequently, although the two PC strategies were similarly effective, NPC proved superior to DPC in terms of energy cost savings and maintaining occupant thermal comfort.