Trade publications are worth skimming even when they are written for someone else. A recent piece from ACHR News, Electrification Changes Heat Pump Design and Specification for MEP Engineers, is aimed at design engineers, not homeowners. The outlet's summary says that as electrification requirements expand, heat pump specification is becoming more complex, and it describes IES Vice President Matthew Duffy discussing the "sizing, electrical capacity, and commissioning challenges" engineers face.
I am not going to claim what the article says beyond that summary. But those three words map cleanly onto a house, and they are exactly where a heat pump quote can go soft. What follows is my own analysis for a homeowner who owns a multimeter and is comfortable in the attic. Before you sign, ask for three things: a load number, an amp number, and a startup sheet.
1. Sizing: ask for the load, not the tonnage
A quote that says "3 ton" and nothing else is a guess in a nice font. Tonnage should be the output of a calculation, not the input. Ask the contractor for the room-by-room heating and cooling load calculation, commonly done with the ACCA Manual J method, and ask what outdoor design temperatures and what home details went into it: square footage, insulation levels, window types, air leakage assumptions.
Then do your own sanity check. Walk the house and confirm the contractor's inputs match reality. Does the report say the attic has insulation you know was never added? Does it count the sunroom as insulated? Bad inputs make a confident wrong answer. If the old system was replaced once already, do not assume its size was right. Equipment is often swapped like for like.
Oversizing is the classic failure. A unit that is too large cycles short, handles humidity poorly, and can feel drafty. An undersized unit leans on its backup heat more than it should. The load calculation is the only thing that tells you which way you are leaning.
2. Electrical capacity: read the label before you read the brochure
Heat pumps are electric, and so is everything else you may be adding. If this install is one piece of a bigger swap, such as a gas furnace, a gas water heater, a range, or a car charger, the service panel is the real bottleneck.
Here is what you can safely do yourself without opening anything. Leave the panel's inner cover on. Read the main breaker rating on the face of the panel, and note the panel's age and brand. Photograph the data plate on any candidate outdoor unit or air handler spec sheet and look for two values: minimum circuit ampacity (MCA) and maximum overcurrent protection (MOCP). Those tell you what wire size and breaker the equipment needs.
Then ask the contractor, in writing, how they confirmed the house can carry the new load. The right answer is a load calculation on the electrical service, done by a qualified person, not a shrug and "it should be fine." If the answer is a panel upgrade or a service upgrade, get that cost into the quote now, so it does not arrive as a surprise change order. Anything inside the panel belongs to a licensed electrician and your local inspector, not to a weekend project.
3. Commissioning: the startup sheet is the product
Commissioning is the part buyers rarely see and the part that decides whether the equipment performs as sold. A new heat pump that is installed but never verified is a box that happens to run.
Ask what the startup procedure includes and ask to keep the record. A reasonable sheet should show things like:
- Refrigerant charge verification by the method the manufacturer specifies.
- Measured airflow or static pressure across the air handler, compared with the manufacturer's range.
- Supply and return temperature readings, so the temperature split is documented.
- Line voltage and running amperage compared with the nameplate.
- A check of defrost operation and the condensate drain.
- Thermostat settings recorded, including any lockouts or changeover points.
You do not need to run these tests. You do need the numbers on paper with a date and a technician's name. If you have a multimeter and the contractor is fine with it, ask to see the voltage reading at the disconnect while the unit is running. A reading that sags badly under load is a conversation worth having on day one, not in January.
The one-page version
Before the deposit, get these in hand: the load calculation and its inputs, the equipment's MCA and MOCP plus the contractor's statement on panel capacity, and a sample or promised startup sheet. A contractor who has done this work regularly will hand those over without friction. One who gets vague when you ask is telling you something useful.
The engineering conversation in the trade press and the one at your kitchen table are the same conversation at different scales. Get the size right, confirm the power is there, and prove the system works once it is running.