đĄī¸ Heating Load Calculator
Calculate your home's heating load to properly size your furnace or heat pump. Based on insulation, window area, and outdoor temperatures.
How to Use This Calculator
Enter your home's square footage and select the insulation quality or R-value. Estimate the total window area in square feet (count all windows). Set the outdoor design temperature â this is the coldest temperature your area typically experiences. Set your desired indoor temperature (usually 68-72°F). Results update in real time.
Understanding Your Results
Your heating load in BTU/hr represents the maximum heating your home needs on the coldest days. The recommended furnace size is rounded up to the next standard size to ensure adequate capacity. The heat pump recommendation considers whether a heat pump alone can handle your climate, or if a dual-fuel system (heat pump + furnace backup) would be more appropriate.
Frequently Asked Questions
What is a heating load?
Heating load is the amount of heat energy (BTU/hr) needed to maintain a comfortable indoor temperature when it's coldest outside. It accounts for heat loss through walls, windows, roof, and infiltration.
How do I determine my furnace size?
Your furnace should be sized to match your heating load. A furnace rated at 80,000 BTU/hr with 95% efficiency delivers about 76,000 BTU/hr of usable heat. Our calculator recommends appropriate furnace sizes.
What is outdoor design temperature?
Design temperature is the coldest temperature expected in your area (typically the 99% design temp from ASHRAE data). It's not the absolute coldest day, but the temperature used for sizing equipment.
Should I get a furnace or heat pump?
Heat pumps are more efficient in mild to moderate climates (above 25°F). In very cold climates, a furnace or dual-fuel system may be better. Use our Heat Pump vs Furnace calculator for a detailed comparison.