Is it cheaper to install a furnace and AC at the same time?

Yes, it is almost always cheaper to install a furnace and air conditioner at the same time rather than separately, with typical savings of 10 to 20 percent on total labor and materials. When you install both together as a complete split system, the contractor can share labor costs such as one trip, one permit, one removal of old equipment, and shared setup of thermostat, line set, drain, and gas connections. For example, installing a furnace alone might cost 3,500 to 6,000 dollars and AC alone 4,500 to 7,500 dollars separately totaling 8,000 to 13,500 dollars, while installing both together typically costs 7,000 to 11,500 dollars for same efficiency, saving 1,000 to 2,000 dollars. Additionally, matched systems from the same brand like Keeprite furnace with Keeprite AC or Carrier furnace with Carrier AC are designed to work together for optimal efficiency, achieving rated SEER2 and AFUE, whereas mismatched old furnace with new AC can lose 10 to 15 percent efficiency. Installing together also ensures both units have same warranty start date and same refrigerant type, important as new R-454B refrigerant phase-in requires matching components. Contractors often offer package discounts and manufacturers offer combo rebates of 200 to 800 dollars for furnace plus AC purchase. If your furnace and AC are both over 12 to 15 years old, replacing together is financially smarter than paying duplicate labor and losing efficiency with mismatched equipment, even if one still works.