Heat Pump Sizing & Manual J Estimator

Heat Pump Sizing & Manual J Estimator

What size heat pump do I need? Seven questions and we work out the real heating and cooling load of your home the Manual J way, not the square-feet guess most calculators use.

  1. Pick the closest match — this sets how cold and how hot it gets
  2. Pick the closest place
    3. Advanced / Custom Input — my climate
    Overrides the looked-up value for your area.
    °F
    °F
  3. Heated living space only — not the garage
    sq ft
    4. Advanced / Custom Input — my home
    Tall ceilings mean more air to heat.
    ft
    1.0 is a square plan, 1.3 a rambling one.
  4. A two-storey home loses less heat than a bungalow of the same size
  5. If you are not sure, go by the age — pre-1980 is usually Poor or Average
    6. Advanced / Custom Input — my insulation
    From a survey or the build spec. Overrides the preset.
    R
    R
    If you have had one done.
    ACH50
  6. Windows lose far more heat than walls, and let the sun in
    7. Advanced / Custom Input — my windows
    From the window sticker. Lower is better.
    BTU/h·ft²·°F
    %
  7. People add heat — it matters in summer
    Decides ducted vs mini-splits
    8. Advanced / Custom Input — how it is used
    Raise it for a home office or a lot of cooking.
    BTU/h
  8. Ducts running through cold spaces waste a surprising amount
    9. Advanced / Custom Input — my ductwork
    From a duct-leakage test if you have had one.
    %
    From the manufacturer’s data. A cold-climate model keeps 85–100%.
    %
We will tell you honestly if it looks oversized. Leave at 0 to skip.
tons
Advanced / Custom Input — change any assumption

Nothing in here is required. Every field is already filled in from your answers above — change one only if you know the real figure from a survey or a datasheet.

Design conditions

°F
°F
grains/lb

The building fabric

R
ft²
R

Gains, ducts and equipment

BTU/h·ft²
BTU/h
BTU/h
%

Your answer

Answer the questions and press “Work out my size”.

This is an ACCA Manual J style estimate, not a certified Manual J report. Estimate only — verify with a licensed electrician/engineer and your local code authority before final installation.

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