The answer to 'difference between system upgrade and' is that a system upgrade involves replacing major HVAC components like the furnace, air conditioner, or heat pump, while a system replacement involves completely removing the old system and installing a brand new one. System upgrades are generally less expensive but may not provide as significant performance or efficiency improvements as a full system replacement.
With a system upgrade, you're updating specific components to improve the overall system's operation, such as replacing an old furnace with a more efficient model or adding a new air conditioner. This can be a more cost-effective option if the rest of your HVAC system is still in good working condition. A system replacement, on the other hand, involves completely removing the old system and installing a brand new one, which provides the opportunity to select a more advanced, energy-efficient system that better meets your home's heating and cooling needs.