Gas/Electric Split Systems
These systems have a gas forced air furnace utilizing either natural gas or liquid propane. The forced air furnace has a evaporative coil attached to it. The coil is connected to the outside condenser. These are a very common type of HVAC system in California. With furnaces up to 97% efficient and air conditioners up to 18 SEER, gas electric split systems are usually the most efficient traditional forced air systems.
Heat Pump Split Systems
These systems are usually found in "all electric" homes. They utilize heat pump technology which is basically air conditioning in reverse. When you want cooling, the refrigerant flows one way, and when you want heating it flows the other way. With SEER ratings up to 18 and EER ratings up to 14, heat pump split systems can be a very efficient option for a traditional forced air system.
Gas/Electric Package Systems
When you see a unit on a roof, it is usually a "gas pack". If it is time to replace your heating and air conditioning system, and you have an old "gas pack" on your roof, then a new gas electric package system will be your least expensive option. They work the same as a gas electric split system except the whole system is housed in one unit. with gas efficiency only reaching 80% and SEER only reaching 16, gas electric package systems are less efficient than other options.
Heat Pump Package Systems
These systems work the same as heat pump split systems, only the whole system is contained in one large unit. Just like a "gas pack", "heat packs" are the least expensive option when replacing an existing package unit. With SEER ratings only reaching 16 and EER ratings only reaching 12.5, heat pump package systems are less efficient than other options.