Furnace Size Calculator

Find the right furnace size for your home by entering the details below.

Understanding Furnace Size Calculations

Choosing the correct furnace size is crucial for ensuring energy efficiency and maintaining comfort in your home. An undersized furnace may struggle to heat your home adequately, while an oversized furnace can lead to inefficiencies and unnecessary costs.

Factors Affecting Furnace Size

The size of the furnace you need depends on several factors, including:

  • Home Size: Larger homes require more heating capacity.
  • Insulation Level: Homes with poor insulation lose more heat, requiring a larger furnace.
  • Climate Zone: Homes in colder climates require more heating capacity than those in warmer climates.
  • Number of Occupants: The number of people in your home can slightly impact heating needs.

How Furnace Size is Measured

Furnaces are typically measured in BTUs (British Thermal Units). A BTU is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. The average furnace size ranges from 40,000 to 150,000 BTU, depending on the home size and other factors.

Common Furnace Sizing Guidelines

While precise calculations are recommended, the following general guidelines can help estimate furnace size based on the square footage of your home and climate zone:

  • Zone 1 (Hot): 20-30 BTU/sq ft
  • Zone 2 (Warm): 30-40 BTU/sq ft
  • Zone 3 (Moderate): 40-50 BTU/sq ft
  • Zone 4 (Cool): 50-60 BTU/sq ft
  • Zone 5 (Cold): 60-70 BTU/sq ft
  • Zone 6 (Very Cold): 70-80 BTU/sq ft

Consequences of Incorrect Furnace Sizing

Properly sizing a furnace is essential for avoiding these common issues:

1. Oversized Furnace

  • Short cycling (frequent on/off cycles)
  • Reduced energy efficiency
  • Uneven heating
  • Higher upfront costs

2. Undersized Furnace

  • Inability to heat your home adequately
  • Constant running, leading to higher energy bills
  • Premature wear and tear

Frequently Asked Questions

Why is climate important in furnace sizing?

Colder climates require more heating capacity to offset heat loss. For example, a home in Zone 6 may need twice the heating capacity of a similar home in Zone 1.

Can I use a heat pump instead of a furnace?

Heat pumps are an excellent alternative for moderate climates. However, in very cold climates, a furnace is often more efficient and reliable.

How often should I replace my furnace?

Most furnaces last 15-20 years. However, upgrading to a more efficient model can save energy costs even before your furnace reaches the end of its lifespan.