QUOTE LINE ITEM · LAST CHECKED NOVEMBER 4, 2026
Manual J load calculation on a heat pump quote: what it should say
Quick answer
A quote should say how the heat pump’s size was chosen, ideally from a Manual J load calculation (the ACCA method for working out how much heating and cooling your house needs), and name the result. If one quote is a size bigger than another and neither shows a calculation, you can’t tell which is right.
What a complete quote states
- That a load calculation was done, the method (for example ACCA Manual J) and who did it.
- The resulting design heating and cooling loads in BTU per hour, and the outdoor design temperature used.
- The equipment chosen and its capacity at your design temperature, not only its nominal tonnage.
- For ducted systems, whether duct design (ACCA Manual D) or a duct check is part of the job.
Red flags when it is missing or vague
- Size chosen by “matching the old system” or by square footage alone.
- No numbers: “properly sized for your home” with no load figures.
- Two quotes a full ton or more apart with no explanation of why.
- A cold-climate home where the quote doesn’t say what the heat pump delivers at low outdoor temperatures.
Three questions to send the installer
- Did you do a room-by-room load calculation such as ACCA Manual J? Can you send me the summary showing the design heating and cooling loads?
- What outdoor design temperature did you use, and how much heat does the proposed equipment deliver at that temperature?
- Why did you choose this capacity rather than one size smaller or larger?
Why two quotes differ here
An installer who calculates the load may arrive at a different size than the system being replaced, especially if the house has been insulated, air sealed or had windows replaced since. A quote that simply copies the old size hasn’t shown that it fits the house as it is now. ENERGY STAR notes that oversized equipment may cycle too often.
Quotes also differ in what they size for. One may cover the whole house with the heat pump; another may assume a backup furnace or electric strips carry the coldest days. Neither is wrong in itself, but they are different proposals and their prices aren’t comparable until you know which is which.
What the sources say
ACCA describes Manual J as “the national ANSI-recognized standard for producing HVAC equipment sizing loads”; its companion, Manual S, covers choosing equipment to meet those loads. A DOE-funded permitting checklist lists “ASHP is sized using ACCA Manual S based on loads determined using ACCA Manual J” as an energy-code item, with a load calculation in the permit submission. Whether your town enforces this varies.
ENERGY STAR advises: “Make sure that your contractor uses the actual characteristics of your home” and warns that “Oversized equipment may cycle too frequently, resulting in less comfort and a shortened lifespan.”
Some rebate programs require it. The NYS Clean Heat manual says heat pumps “shall be sized in accordance with ACCA Manual S … based on design loads calculated in accordance with ACCA Manual J” and that sizing “shall not be based on nominal size or AHRI rated capacities.” Efficiency Maine’s claim form asks for a sizing worksheet. Mass Save’s partial-home sizing bonus requires sizing to 90–120% of the heating load per Manual J design conditions.
Cost
We don’t publish a price for a load calculation. Many installers include it in the quote; some charge separately. Ask whether it is included.
Sources
- Manual J (ACCA)
- Manual S (ACCA)
- HVAC Quality Installation (ENERGY STAR)
- Heat Pump Space Heating Permitting & Inspection Checklist (PDF) (New Buildings Institute for the U.S. DOE, page dated October 2024)
- NYS Clean Heat Program Manual v2 (PDF) (NYS Clean Heat, page dated March 5, 2026)
- Residential heat pump claim form (PDF) (Efficiency Maine)
- Mass Save 2026 air-source heat pump rebate form (PDF) (Mass Save sponsors, page dated 2026 installs)
Holding two or three quotes? Mark Equipment as Included, Excluded or Unclear for each quote and get one question list per installer. Nothing is uploaded.
Last checked: . Informational only. This is not financial, tax, legal or professional installation advice, and we do not verify any installer’s work.