Globally, food security is facing increasingly severe challenges. Rapid population growth and intensifying climate change have placed greater pressure on agricultural production. As an environmentally controllable modern agricultural system, plant factories demonstrate significant potential in addressing food security issues; however, their high energy consumption and operating costs hinder large-scale application. To address this, this paper takes lettuce cultivation as an example to study methods for improving the energy efficiency and economic performance of plant factories through participation in power grid demand response. By analyzing the characteristics of lighting and air-conditioning loads, a load regulation model is developed, and optimal scheduling is conducted under a time-of-use pricing mechanism with the objective of minimizing electricity costs. Simulation results show that the proposed strategy reduces the total electricity cost of the plant factory by 30.1%, verifying the feasibility of effectively alleviating operational cost pressures through demand response.