What to Expect From a Heat Pump in a Michigan Winter

Somebody who had a heat pump put in last spring calls us in November, and the wording barely changes from one year to the next: it's blowing cold air and there's smoke coming off the thing outside.

Nothing is wrong. That's a defrost cycle, it's supposed to do that, and the steam is water evaporating off a warm coil. But nobody told them, and now they're standing in the backyard in a bathrobe convinced their new system is failing.

That's the problem with heat pumps in this climate. The equipment is fine. Cold-climate models handle a West Michigan winter far better than their reputation suggests. What trips people up is that a heat pump behaves nothing like the furnace it replaced, and almost every installer forgets to explain that before they drive away.

It Feels Cooler Because It Is Cooler

Start with the complaint I hear most: the air coming out of the vents isn't warm.

A gas furnace burns fuel and delivers air somewhere in the 120 to 140 degree range. It arrives hot, in short bursts, and when you hold your hand over a register there's no question the heat is on.

A heat pump doesn't make heat, it moves it, pulling warmth out of outdoor air, even cold outdoor air, and bringing it inside. What comes out of your registers is typically in the 90 to 95 degree range.

Now, your skin sits at about 98.6 degrees. Ninety-two-degree air is below that. So it feels cool on your hand, even though it's well above room temperature and heating your house perfectly well.

That one complaint accounts for more unhappy heat pump owners than everything else put together, and it isn't a defect. It's the trade: lower temperature, much longer runtime, and a steadier house as a result. Most people find that once they stop checking the register and start checking the thermostat, the complaint goes away. The rooms are actually more even than they were with the furnace, because air is moving almost all the time instead of in ten-minute blasts.

That brings up the second call.

Running Constantly Is the Point

A furnace that ran nonstop would worry me. A heat pump that runs nonstop is doing exactly what it was designed to do.

These systems are built to match your house's heat loss at a low, continuous output rather than overshooting and shutting off. In genuinely cold weather a properly sized heat pump may run close to continuously, and that's the efficient way to operate. Short cycling would be the symptom here, not long runtimes.

It also means the outdoor unit is running in the winter, which surprises people who think of that box as "the air conditioner." Same box, reversed. It'll be humming away on a February night, and it should be.

The Defrost Cycle, Explained Once

This is the one worth understanding in detail, because it looks alarming and it's completely routine.

In cold, damp conditions (which is most of a West Michigan winter, downwind of a big lake), moisture in the outdoor air condenses on the outdoor coil and freezes. A layer of frost insulates that coil, and an insulated coil can't absorb heat.

So the system deals with it. Periodically it reverses itself and runs in air conditioning mode for a few minutes. The outdoor coil gets hot, the frost melts off, and then it flips back to heating.

From your side, here's what that looks like:

• The outdoor fan stops. Sudden quiet, which people notice.
• Steam rolls off the outdoor unit. That's melted frost evaporating off a warm coil, not smoke.
• The indoor air turns cool, because the indoor coil is now the cold one.
• Backup heat usually comes on to temper that air so the house isn't getting chilled, and you may see an AUX light on the thermostat.
• Five to fifteen minutes later it's over, sometimes with a shudder or a whoosh as the reversing valve shifts back.

How often depends on conditions, but somewhere in the range of every thirty to ninety minutes during frosty weather is ordinary. Dry cold triggers it less. That damp thirty-three-degree drizzle we get so much of triggers it plenty.

What's not normal: the unit encased in solid ice rather than frost, ice building on the fan blades, a defrost cycle that runs for a half hour, or no defrost happening at all while the coil disappears under a white shell. Those mean a sensor, board, or reversing valve issue and they're worth a service call.

AUX and EM HEAT Are Not the Same Thing

This distinction costs people real money every winter, and the labels do nothing to help.

AUX — auxiliary heat — is automatic. When the heat pump alone can't keep up, the system brings in backup: electric resistance strips in the air handler, or a gas furnace in a dual-fuel setup. The heat pump keeps running and the backup fills the gap. Seeing AUX on a cold morning or during a defrost cycle is normal.

EM HEAT — emergency heat — is a manual setting, and it shuts the heat pump off completely. Everything comes from backup.

Electric strip heat is the most expensive way to warm a house. It's roughly like heating with a bank of giant toasters, and running on it for a week will produce a bill people remember for years.

The mistake is predictable: the house feels a little chilly, somebody finds EM HEAT on the thermostat, thinks "emergency, it's cold, that's what this is for," and flips it. Then they leave it there.

Emergency heat is for when the heat pump is genuinely broken — outdoor unit not running, no heat at all — and you need warmth until somebody can get there.

If AUX is coming on constantly in mild weather, that's not you doing anything wrong, that's a symptom. A refrigerant charge problem, a defrost control issue, a thermostat configured for the wrong equipment, or a system undersized for the house will all do it. Worth a call.

Setbacks Work Backward Here

Everything you know about thermostat setbacks from a gas furnace needs adjusting.

With a furnace, dropping the temperature eight degrees overnight saves fuel and the furnace muscles it back in the morning. Fine.

With a heat pump, that morning recovery is the problem. Asking a heat pump to climb five degrees quickly is asking for more output than it can deliver, so the thermostat brings on the strips, and you burn more in twenty minutes of resistance heat than you saved all night.

So: small setbacks, two degrees or so, or none at all. Or use a thermostat that's genuinely set up for heat pump operation, which will ramp the recovery gradually and avoid calling for backup. The fall thermostat guide goes through the numbers in more detail, but the short version is that a heat pump wants to be left alone more than a furnace does.

What Actually Needs Attention

Keep the outdoor unit clear. Snow drifted against it, a roof line dumping on it, or leaves packed into the coil all choke it. It should be sitting up on a stand or risers so there's room underneath for meltwater and snow, and if yours is at grade level and getting buried, that's worth fixing before December.

Service it twice a year. This is the real difference from a furnace. A furnace sits idle half the year; a heat pump works in both seasons, so it accumulates roughly double the runtime. Refrigerant charge matters more than people realize here. A system slightly low on charge will still cool acceptably in July and then lean hard on backup heat all winter, and you'll never know except through the electric bill.

Watch your bills the first winter. Electric goes up and gas goes down or disappears. Compare total energy cost, not one line item, or you'll scare yourself for no reason.

I installed a system for a family in Caledonia, and in early December the homeowner called me twice in one week — first about the cold air at the registers, then about the steam outside. Both times I talked her through it on the phone. Then in January she called a third time, and that one was real: AUX was on nearly all day in thirty-degree weather, which shouldn't happen. The outdoor sensor had failed, so the control board thought it was far colder than it was and was calling for strip heat almost continuously. Ninety-dollar part. Her February bill went back to normal.

Two calls that were nothing and one that wasn't. I'd rather take all three than have her spend a winter assuming anything odd was fine.

The Honest Summary

A cold-climate heat pump is a legitimate choice for a West Michigan house, and the ones going in now hold their capacity much further down the thermometer than the units that gave them a bad name twenty years ago. Whether it's the right choice against a gas furnace at your house depends on your rates, your insulation, and whether you already have gas service. That comparison is its own conversation.

But if you already have one, the winter adjustment is mostly about expectations. Cool air at the registers is normal. Continuous runtime is normal. Steam and a cold blast for ten minutes is normal. EM HEAT is not a cold-weather setting. And an outdoor unit under a snow drift is a problem you can solve with a shovel.

Heat pump service in Jenison, Hudsonville, Grandville and across the Grand Rapids area is work we do year-round, and I'd rather answer a question in November than a no-heat call in February.