Group 1 - The article discusses the energy-saving strategies for air conditioning usage when leaving home for a short period, specifically comparing fixed-frequency and variable-frequency air conditioners [3][7]. - Fixed-frequency air conditioners consume a constant amount of energy, and it is more economical to turn them off when leaving for a few hours [3][5]. - Variable-frequency air conditioners are more efficient when left on for short periods, as they consume less energy during operation compared to the energy required to restart [3][7]. Group 2 - The lifespan of air conditioners is primarily determined by the compressor, and minimizing the frequency of on-off cycles can extend the life of fixed-frequency models [7]. - Variable-frequency air conditioners operate at lower power levels, which can help prolong their lifespan if not frequently turned off and on [7]. - Safety concerns are raised regarding leaving air conditioners running while away from home, particularly if the unit is old or improperly installed, which could lead to fire hazards [8][9].