Sizing screen

Heat Pump Sizing Calculator

Check whether the tonnage in your contractor's quote deserves an explanation before you sign. You get a rough comparison range, not a fake equipment selection, plus the exact Manual J and low-temperature questions the quote still needs to answer.

Quick answer

Square-foot rules cannot size a heat pump. This tool returns a broad range where the shortcut remains useful, and stops large projects before an aggregate number creates false precision.

Your home and quote

Build a range worth questioning

Floor area starts the comparison. Climate, envelope, and ceiling height adjust it. Ducts change the installation questions, while the contractor's quoted tonnage shows whether you need a better explanation.

Conditioned square feet

Heated and cooled floor area only. Accepted range: 300 to 10,000 sq ft.

Average ceiling height

Use the average across conditioned rooms. Accepted range: 7 to 14 ft.

Climate

Choose the closest winter context. This is not a local design temperature.

Envelope

Choose poor for drafty or older construction, and good for an upgraded tight envelope.

Duct situation

Duct choice changes the installation plan, not this rough numeric range.

Contractor's quoted tonnage (optional)

Enter total nominal tonnage across all quoted systems, or leave blank. Accepted range: 0.5 to 70 tons.

Reviewed July 12, 2026

How this rough comparison works

1. Build a midpoint. Conditioned area is multiplied by a climate screen, an envelope factor, and a capped ceiling-height factor.
2. Make uncertainty visible. The tool expands that midpoint by 15 percent in both directions and rounds the BTU edges outward.
3. Stop when the shortcut stops helping. Projects above the 20-ton rough-comparison ceiling move to a multi-system review without an aggregate range.
4. Compare, do not select. Quoted tonnage is checked against the band. Duct condition changes the questions and project scope, not the numeric shortcut.

The result omits room-by-room exposure, measured infiltration, solar gain, occupancy, ventilation, local design temperature, and model-specific performance. A contractor must resolve those before equipment selection.

Primary sizing sources

ACCA Manual J overview defines the residential room-by-room load-calculation standard that contractors should use before selecting equipment.
ENERGY STAR air-source heat pump guidance explains rated performance and the importance of climate-appropriate equipment selection.
US Department of Energy cold-climate sizing guidance covers design temperature, capacity at low outdoor temperatures, backup heat, and cold-climate sizing tradeoffs.

These sources support the professional checks and model limits. They do not validate the tool's editorial BTU-per-square-foot factors as a load calculation.

Heat pump sizing FAQ

Does this replace a Manual J load calculation?

No. It is a broad comparison screen built from floor area, climate, envelope, and ceiling height. Equipment selection still requires a room-by-room Manual J using the actual home and local design temperature.

Do existing ducts change the range?

Not in this rough model. Duct condition changes distribution, airflow, static pressure, comfort, and project scope. A contractor must inspect those separately instead of hiding them inside a tonnage shortcut.

Why does the calculator show a range?

The inputs cannot support one defensible tonnage. The range makes the uncertainty visible and gives you a comparison point for the contractor quote without pretending to select equipment.

What happens on a large or multi-system project?

If the inputs put the project above the tool's 20-ton rough-comparison ceiling, it stops before showing an aggregate tonnage band. Ask for a room-by-room Manual J, a system-by-system schedule, and model capacity at the local design temperature.