Complete Gas systems are very efficient as your home HVAC system and Goodman 3 Ton 16 SEER Single-Stage Gas System is a fine choice. The complete Gas system consists of – Goodman 80000 BTU Two Stage Gas Furnace GME80603BN, Goodman 3 Ton 16 SEER Two Stage Air Conditioner Condenser GSX16S361 and Goodman 4 Ton Evaporator Cased Coil CAPF3137B6.