# Heat pump sizing and Manual J

Ask for a documented load calculation instead of a floor-area shortcut.

Updated 2026-11-10. Also on the [web page](https://heatpumppros.fyi/guides/sizing-and-manual-j).

Heat pump sizing starts with the home. Ask your bidder to show the heating and cooling load calculation before you accept an equipment size.

ACCA describes Manual J as a residential load calculation standard. It covers inputs used to determine heating and cooling demand. A calculated load is not the same as the nominal capacity printed in a product name.

## Give the designer accurate inputs

Prepare a floor plan if you have one. Point out additions, insulation work, replacement windows and rooms that are hard to heat or cool. Ask how the calculation represents air leakage, duct location and local outdoor design conditions.

If you plan to improve insulation before installation, tell the designer. Ask whether the final equipment selection will use the home as it is now or the home after that work. Keep the assumptions with the report.

## Request useful outputs

Ask for room-level heating and cooling loads, the total load and the outdoor design temperatures. Ask which parts of the home the proposed system serves. A quotation based only on the existing furnace size leaves these questions open.

Have the designer compare the selected equipment's actual output with those loads. For cold-climate equipment, ask for low-temperature performance for the exact matched system. NEEP's product information can support that comparison.

## Treat online tools as planning aids

A sizing app can help organize measurements and assumptions. It cannot inspect hidden ducts or confirm every input in your home. Ask an installer to review the data and take responsibility for the final design.

Do not use this site's energy-cost estimator as a substitute for a load calculation. It can compare a proposed capacity with a load you already have. It does not infer equipment size from floor area or select a system.

## Sources

All pages below were fetched and checked on 2026-11-10. The check date is not a promise that intake remains open.

- [ACCA, Manual J Residential Load Calculation](https://www.acca.org/standards/technical-manuals/manual-j). Checked 2026-11-10.
- [NEEP, ccASHP Specification and Product List](https://neep.org/heating-electrification/ccashp-specification-product-list). Checked 2026-11-10.
- [Government of Canada, Electric heat pumps and NRCan resources](https://www.canada.ca/en/environment-climate-change/services/energy-efficiency/heat-pumps.html). Checked 2026-11-10.

## Questions

### Can I size a heat pump from floor area alone?

Ask for a documented load calculation that represents the home and local conditions. Floor area alone does not document those inputs.