Leave it on auto heat and set the temperature where you want it, then leave it alone. Don't bump it up and down through the day and don't switch over to emergency heat unless the outdoor unit is iced over and not defrosting, or the system can't keep up during a hard cold snap. Illinois winters bring stretches of real cold, and a heat pump has to work harder to pull warmth out of that outside air than it does on a mild day. Emergency heat skips the outdoor unit and runs on backup electric resistance heat instead, which costs more to run. Most heat pumps here are paired with a gas furnace for backup, and that system is built to switch over on its own during the coldest stretches. Leaving the thermostat set and letting the system manage the transition between the heat pump and the furnace backup is what keeps the setup working the way it was designed to, and it's the setting that costs you the least over a winter.
A heat pump pulls warmth from outside air, and the colder that air gets, the harder it has to work to find any. Below a certain outdoor temperature, usually somewhere in the 30s, the system can't pull enough heat on its own and the backup heat strip turns on to cover the gap. That's normal for an Illinois winter. It's only a problem if the backup heat is running constantly instead of kicking in for short stretches on the coldest days.
Some frost on the outdoor unit during winter is normal, and the system defrosts itself on a timer, switching briefly into cooling mode to melt it off before going back to heating. A unit that's solid with ice and not clearing on its own usually points to a problem with the defrost control, a sensor, or airflow across the coil. Since power here isn't cheap, a coil that can't shed ice efficiently is pulling more electricity than it should to make the same heat.
Most houses in Illinois heat with gas, so a heat pump in your house is probably doing the job alongside a furnace, not alone. If you've been switching it to emergency heat every cold snap, you're asking that backup furnace to carry the whole load, and with power costs here, that shows up fast on the bill. Leave it on auto and let the heat pump pull as much warmth from the air as it can before the furnace has to step in.
If the thermostat isn't holding steady, or the backup heat seems to run more than it should for how cold it actually is outside, that's worth having someone look at before it costs you a full winter of higher bills. A local contractor who works on heat pumps all season knows what tends to go wrong in weather like this, and knows the difference between a system that's working as designed and one that's compensating for something failing. Get matched with one who services your area and your equipment, and they'll reach out directly, no need to field calls from more than one company.
Across Illinois, the summer dew point averages 63°F over June, July and August, according to NOAA climate data. That's heavy, sticky air, and your heat pump is pulling double duty in weather like that, wringing out humidity as it cools. A system that's not maintained loses ground on that job before it loses ground on temperature, so the house can feel cool but still damp. That's a coil and airflow issue as much as a thermostat setting, and it's worth having someone local look at before the humid stretch sets in, someone who services this equipment all year and knows what tends to give out first in weather like this.
NASA POWER T2MDEW county cells weighted by homes
A licensed local pro takes the request for your heat pump tune-up.
There's no charge for the request.
The unit sits clean on its pad, coils clear, nothing blocking the airflow around it. Set on auto heat and left alone, it cycles on and off in short stretches instead of running flat out. That's a heat pump doing what it's built to do.
Dirt and grime coat the coil, and the ground around it has gone bare. A unit working this hard all winter, especially one that's older, is worth having checked before the next cold snap. Maintenance catches a dirty coil before it turns into a system that can't keep up.
You stand by the vent and the air coming out feels cool, not cold, but not what you'd call warm either, and the system just keeps running. You start to wonder if it's actually doing its job or if something's wrong with it.
A furnace burns gas and pushes out air hot enough to feel right away. A heat pump works differently. It pulls warmth out of the outside air and moves it into your house, so the air coming out of the vent usually sits somewhere around body temperature, warm enough to heat the room but not hot to the touch. That's why it runs longer, in steady stretches, rather than short hot bursts. On a cold Illinois day the outside air holds less warmth to begin with, so the system has to move more of it to keep up. As long as the house is slowly warming and the unit isn't icing over, that long runtime is the heat pump working the way it's built to.
Grass trimmed back, mulch bed clear, nothing crowding the cabinet. Air moves through the coil the way it's supposed to, so the unit pulls heat out of cold air without a fight. A heat pump kept clear like this holds its cycle and doesn't lean on the furnace more than it has to.
Set flush against the siding with nothing but bare concrete around it, this unit has no room to breathe. Dirt and debris collect against the cabinet faster, and if a service tech ever needs to get at the coil or the disconnect, there's barely room to stand. Airflow suffers before you notice anything on the thermostat.
At 17.67 cents a kilowatt-hour, every hour your heat pump leans on backup strip heat instead of its own compressor shows up on the bill. That's the real cost of flipping to emergency heat during a cold snap instead of letting the system work the way it's set up to.
EIA-861 2025 statewide residential average
Set it on auto heat, pick a temperature, and leave it there through the cold months. That's the whole answer. The system is built to run long and steady, pulling what warmth it can from outside air, and it only needs help when ice builds up on the outdoor coil and won't clear, or when the air outside gets cold enough that the compressor alone can't keep the house at temperature. Everything else, the short cycles, the long runtimes, the air that feels cool instead of warm at the vent, is the system doing its job the way it was designed to.
If yours runs next to a gas furnace, it still needs that steady setting. Flipping to emergency heat out of habit just means the furnace is carrying the whole load while the heat pump sits idle, and the bill shows it.
What usually knocks a system off that steady pattern is buildup on the coil or a defrost cycle that isn't clearing it, and that's exactly the kind of failure a contractor who works on heat pumps all winter in this state has seen before and knows how to spot early. Request a match here and you're connected with one licensed contractor local to you, not a handful of companies competing for the callback. Someone who already knows what an Illinois winter does to this equipment is the one who shows up.
Your request goes to one pro, not a list of companies.
You only hire the pro if you want to.
