HVAC & Water Heating Calculators

Size air conditioners and estimate furnace and AC replacement costs.

Heating and cooling equipment is a major purchase, and size matters as much as price. An air conditioner that is too small cannot keep up on hot days, while one that is too large turns on and off too often and leaves the house humid. Before you talk to an HVAC contractor, it helps to know roughly what size and budget to expect.

The AC tonnage calculator uses the ENERGY STAR room chart for single rooms and a climate-based rule of thumb for whole houses. The replacement cost calculator turns that size into an installed price range for a furnace and AC, AC only, furnace only or a heat pump. Both tools explain their assumptions, and both remind you that a contractor should confirm sizing with a Manual J load calculation.

Furnace and AC Replacement Cost CalculatorFurnace, central AC or heat pump installed cost by size.AC Tonnage CalculatorAir conditioner size in BTU and tons for a room or house.

Tips before replacing HVAC equipment

Ask each contractor how they sized the system. A Manual J load calculation is the standard method.
Have the ductwork inspected. Leaky ducts can waste much of what a new system saves.
Compare warranties on both the equipment and the installation labor.