Heating System Sizing Guide: How to Calculate the Right Furnace or HVAC Unit Planning to install or replace your home heating system? It’s critical to get the size right. A system that’s too small will struggle and underperform, while one that’s too large will short-cycle, waste energy and wear out faster. At Gunny’s Air Conditioning & Plumbing, we’ve published this detailed Heating System Sizing Guide that walks homeowners through: https://callgunnys.com/blog/heating-system-sizing-guide/