The answer to 'when to replace system upgrade' is that most HVAC systems last 15-20 years with proper maintenance. If your system is over 10 years old, it's a good idea to start planning for a replacement in the next few years. Older systems become less energy-efficient and more prone to breakdowns, so upgrading can save you money on utility bills and unexpected repair costs.
When considering a replacement, look for high-efficiency models that meet the latest energy standards. This will provide long-term savings and reduce your environmental impact. It's best to work with a qualified HVAC technician to ensure you get the right system for your home's size and needs.