Furnace System GuideFurnace tools
Furnace Tools: BTU Sizing, Efficiency, and Operating Cost
Client-side furnace tools for estimating heating BTU load, comparing AFUE efficiency, and estimating annual operating cost by fuel.
Furnace BTU Sizing Calculator
Estimate required furnace heat output and input BTU per hour from home square footage, a climate factor, and AFUE before getting a professional load calculation.
CalculatorFurnace Operating Cost Calculator
Estimate annual heating therms and natural gas cost from furnace input BTU, AFUE, daily run hours, season length, and your gas rate.
CalculatorAFUE Upgrade Savings Calculator
Estimate annual fuel savings from moving to a higher AFUE furnace using your current heating cost and both efficiency ratings.
CalculatorFurnace Repair or Replace Calculator
Weigh furnace age, repair cost, and new furnace cost with a clearly labeled rule of thumb to lean toward repair or replacement.
CalculatorFurnace Oversizing Check
Compare a furnace output rating against your home design heat loss to screen for an oversized furnace that can short cycle and waste comfort.