How to Set Expectations for the First Heat Pump Winter

Why this matters

The callback that follows a furnace-to-heat-pump conversion is rarely a broken system. It is a working system that does four things the customer has never seen a heating system do: it blows air that feels cool on the hand, it runs for hours, it stops in the middle of a cold night and puffs steam outside, and it lights up a word on the thermostat that sounds like failure. Each of those is normal, each one sounds like a defect to someone raised on a furnace, and each one costs a truck roll in January if nobody said it in October.

The second cost is quieter. A customer who keeps their furnace habits, especially a deep overnight setback, can push the house onto electric resistance backup every morning and get a first winter bill that confirms every fear they had about going electric. This article is the handover conversation and the written sheet that prevents both. The component behavior itself (capacity falling with outdoor temperature, how defrost is triggered) belongs to the cold-weather operation card; this one is about what you say, in what order, and what you leave on the fridge.

Step 1: Hold the conversation at the thermostat and the outdoor unit, not in the driveway

Walk the customer to the thermostat first, then outside to the unit. The reason is that every point below has a physical thing attached to it: the display word, the supply register, the fan on the outdoor unit, the drain path under it. A customer who has seen the word "AUX" on their own screen while you explained it will recognize it at 6 a.m.; one who heard about it across the truck bed will not.

Book fifteen minutes for this on the install ticket as its own line. If it is not on the ticket it becomes the thing done while the helper loads the van, and the customer gets two sentences.

What breaks if you skip it: the conversation happens anyway, by phone, after the first cold night, with the customer already worried and you guessing what their screen says.

Step 2: Reset what "warm" means before they put a hand on a register

A gas furnace typically delivers supply air somewhere around 120 to 140 F. A heat pump in heating commonly delivers air in the 85 to 105 F range, lower when it is colder outside and the airflow is high. Skin on the back of a hand sits a little above 90 F, so moving air at 95 F feels cool even while it is heating the house. Tell them this before they test it themselves, because the first thing almost every converted customer does is hold a palm over the register.

The frame that works is volume, not temperature: the furnace delivered heat in hot bursts, the heat pump delivers it in a long, mild stream. The room temperature is the measure, not the register.

TECH: Put your hand here. Feels lukewarm, right?
CUSTOMER: Honestly, yeah. Is that it?
TECH: That's it working. Your furnace pushed air around
      130. This pushes air in the 90s, a lot longer.
CUSTOMER: So the house will get warm?
TECH: Watch the thermostat, not the vent. If it holds
      the number you set, it's doing its job. If the
      room drops two degrees below the setting and
      stays there, that's when you call us.
CUSTOMER: And this word up here, AUX?
TECH: That's backup heat helping. Some mornings it
      will come on. If it's on all day when it's not
      that cold out, call us. That's worth a look.

Note what the tech gave the customer: a number that means trouble (two degrees under the setting and staying there) and a pattern that means trouble (backup heat all day in mild weather). A customer with a trouble threshold does not call on the normal cases.

Step 3: Explain long run times as the design, not a symptom

A furnace sized with typical margin heats in short cycles and sits idle between them. A variable-speed heat pump is built to run long at low output, and on the coldest days a correctly sized unit may run nearly continuously. Customers read a system that never stops as a system that is struggling.

Say it plainly: "On a cold day it may run all day. That's normal. What's not normal is running all day and the house falling behind." That ties run time back to the same trouble threshold from Step 2, so the customer has one rule to remember instead of two.

What breaks if you skip it: the customer turns the thermostat up to "help it catch up", which on many setups brings on backup heat sooner and changes nothing about how fast the compressor can heat.

Step 4: Change the setback habit, with the arithmetic in hand

This is the step with money attached, and it is the one most installers skip because it sounds like nagging. A deep overnight setback that saved fuel on a furnace can cost money on a heat pump, because the morning recovery is a large demand at the coldest hour of the day. If the compressor cannot close the gap within the thermostat's recovery window, the thermostat calls for backup heat, and electric resistance strips make one unit of heat per unit of electricity where the compressor makes two or three.

Give a concrete recommendation rather than a principle. A common starting point, tuned to the house and the thermostat: setback of no more than 2 F, or none, on a heat pump with strip backup; and, where the thermostat supports it, an outdoor-temperature lockout that keeps the strips off above a set temperature (installers often start around 30 to 35 F and adjust after the first cold snap). Set the lockout yourself before you leave and write the value on the sheet.

Dual-fuel systems that keep a furnace as backup behave differently, and their changeover point is a separate decision. See related: Backup Heat: Dual Fuel or Resistance.

Step 5: Show them where defrost happens and what it looks like

In weather near freezing with moisture in the air, frost builds on the outdoor coil and the unit periodically reverses to melt it. What the customer will see and hear: the outdoor fan stops, there is a whoosh as the valve shifts, a cloud of steam rises off the unit, and water runs out underneath. Indoors, the air may feel cooler for a few minutes. In frosting weather this can repeat roughly every half hour to hour and a half of run time and last a few minutes each time, varying by equipment and conditions.

Stand at the outdoor unit and point at three things: the coil that frosts, the base where meltwater drains, and the ground under it where ice can build. Then give them the snow and ice rules, each with its hazard: keep the top and sides clear of snow by brushing it off by hand or with a soft broom; never chip ice off the coil or fins with a tool, because the fins tear and the coil can be punctured; never reach through the fan guard, because the fan can start without warning on a call for heat; and if ice has built up into the unit, switch it off at the outdoor disconnect and call rather than clearing it. Do not cover the unit in winter; a heat pump needs that coil open all season.

The steam cloud is the single most common "is it on fire" call. One sentence prevents it.

Step 6: Separate "AUX" from "EMERGENCY" on their screen

Thermostats name these differently, so use the words on this customer's screen. Two states matter:

• Auxiliary heat comes on automatically when the heat pump needs help: during recovery, during defrost, or below the balance point (the outdoor temperature where the house loses heat faster than the compressor alone can supply it). Normal in cold snaps, normal briefly in defrost.
• Emergency heat is a manual setting that locks out the compressor and heats on backup only. It exists for when the outdoor unit has failed. Left on by mistake, it runs the house entirely on resistance heat.

Tell the customer never to select emergency heat unless you tell them to, and show them how to tell if it got set by accident. A grandchild or a house sitter flipping it on is a real source of a first-winter bill shock.

Step 7: Leave a written sheet, and schedule the first-cold-snap call

The sheet is one page, taped inside the furnace closet door or on the air handler, and a copy in the customer's job record. It carries what the customer needs at 6 a.m. without you:

• the trouble threshold (room 2 F under setting and staying there; backup heat running all day above the lockout temperature);
• the setback setting and the strip lockout temperature you programd;
• the defrost description in one sentence;
• the snow and ice rules with "switch off at the disconnect" spelled out and the disconnect's location named;
• what emergency heat is and how to turn it off;
• the bill expectation: compare winter bills in kilowatt-hours across months, and expect the first bill after a cold snap to be the highest;
• your phone number and the job number.

Then put a follow-up on the schedule: a call within 48 hours of the first night below about 20 F, and a second after the first full winter billing cycle. The first catches settings and behavior; the second catches a bill that does not match expectations while there is still a winter left to adjust.

Worked example: the setback that showed up on the bill

Illustrative figures, labeled as such. A converted house has a cold-climate variable-speed heat pump and 10 kW of strip backup. The owner kept their furnace habit: 68 F by day, 60 F overnight, back to 68 F at 6 a.m. Nobody set a strip lockout.

On cold mornings the heat pump cannot recover 8 F inside the thermostat's window, so the strips run. Say they run about 2 hours on each of 90 cold mornings in the season: 2 hours times 90 mornings is 180 hours, and 180 hours at 10 kW is 1,800 kWh of resistance heat. Resistance turns each kWh into 3,412 BTU, so that is about 6.1 million BTU. The compressor, at an illustrative coefficient of performance of 2 in that weather, would have made the same 6.1 million BTU from about 900 kWh. The setback habit cost roughly 900 kWh of extra electricity in one winter, before counting whatever the setback itself saved overnight.

At the first-bill call the tech asked to see the thermostat's runtime report, found the daily aux hours, and changed two things: setback reduced to 2 F, strip lockout set at 30 F. The owner's next month, in similar weather, showed aux hours near zero on mornings above 30 F.

What would change the answer: on a dual-fuel system the morning recovery runs on the furnace, so the trade-off is the cost of gas against electricity, not strips against compressor; and on a home where the heat pump has large margin at design conditions, a deeper setback may recover on the compressor alone. The thermostat's runtime report settles which case you have.

How to tell the handover worked

Ask the customer to tell you back, in their own words, three things: when to call (the threshold), what the steam is, and what not to touch on the thermostat. If they cannot say the threshold, you have not given them one. Check the sheet is posted where you said, with the lockout value filled in rather than blank. And watch your own call log: converted customers calling in the first winter about cool air, steam or "AUX" are the measure of whether this conversation is being held or skipped.

References

• See related: Heat Pump Cold-Weather Operation Reference
• See related: Heat Pump Defrost Cycle Reference
• See related: Backup Heat: Dual Fuel or Resistance
• See related: How to Walk a Customer Through an Electrification Plan
• Equipment manufacturer installation and thermostat configuration instructions for the installed system (lockout, recovery and staging settings)