HVAC & Energy Systems

Size Your HVAC System and Energy Equipment Correctly

HVAC is the most expensive system to get wrong. An undersized unit runs constantly and never keeps up; an oversized unit short-cycles, causes humidity problems, and wears out compressors prematurely. The rule of thumb — 400 to 600 square feet per ton of cooling — is only a starting point. Actual requirements depend on ceiling height, insulation levels, window area, and climate zone. These calculators give you a proper load estimate before you call an HVAC contractor or shop for equipment.

Sizing Heating and Cooling Equipment

Start with the HVAC Sizing Calculator to estimate BTU requirements using square footage, ceiling height, insulation R-value, and climate zone. A well-insulated 2,000 sq ft home in Zone 4 typically needs 2.5 to 3 tons of cooling (30,000-36,000 BTU). For ductless systems, the Mini-Split Sizing Calculator handles multi-zone setups and calculates the required capacity for each zone independently.

Adding central air or replacing an aging system? The AC Unit Size Calculator provides a load-based recommendation rather than just matching the old unit size — which may itself have been oversized. For humidity control, the Dehumidifier Size Calculator recommends pint capacity based on room size and moisture level. The Ceiling Fan Size Calculator matches blade diameter to room dimensions for effective air circulation.

Duct Sizing and Airflow

Even a properly sized HVAC unit underperforms if the ductwork can't deliver adequate airflow. The Duct Sizing Calculator ensures each supply run delivers sufficient CFM to each room. The CFM Calculator converts room volume and air changes per hour to the cubic feet per minute each room needs — a 12x15x9 ft bedroom at 6 ACH needs 486 CFM from the supply register.

Insulation and Energy Savings

Insulation R-values vary by climate zone: Zone 4 requires R-38 in attics and R-15 in walls; Zone 6 requires R-60 attic and R-20 walls. The Attic Insulation Calculator determines how much blown-in or batt insulation you need to reach your target R-value based on existing insulation depth. The Insulation Savings Calculator shows the payback period against your current heating and cooling costs.

Considering a heat pump? The Heat Pump Savings Calculator compares annual operating costs against your current furnace and central AC setup. Most homeowners switching from a gas furnace to a cold-climate heat pump see 30-50% savings on heating costs. Track ongoing energy use with the Electricity Cost Calculator and the Appliance Energy Cost Calculator to identify the biggest consumers in your home.