Heat Pump Auxiliary Heat: Why Your Winter Bill Jumps on Cold Panhandle Nights

If your electric bill jumps after the first cold snaps of a Panhandle winter, the most common cause in homes with a heat pump is auxiliary heat: the backup electric-resistance coils that switch on when the heat pump alone cannot keep up. Auxiliary heat makes heat the expensive way, so knowing when it runs, why it runs and how to keep it from running more than it needs to is one of the simplest ways to keep winter bills in check.

What auxiliary heat actually is

A heat pump does not create heat in the normal sense. In winter it pulls heat out of the outdoor air and moves it indoors, using the same refrigerant loop that cools your house in summer, just running in reverse. Because it is moving heat rather than making it, a heat pump uses much less electricity for the same amount of warmth than a space heater or a furnace with electric coils.

Most heat pumps in the Florida Panhandle are installed with an electric heat strip inside the air handler. That strip is a set of resistance coils, the same basic idea as a toaster or a hair dryer. Your thermostat calls it "auxiliary heat" (often shown as AUX) when it runs automatically alongside the heat pump, and "emergency heat" (EM HEAT) when you switch to it manually and the heat pump is turned off.

Resistance heat turns one unit of electricity into one unit of heat. A heat pump in mild weather delivers several units of heat for each unit of electricity it uses. That gap is why an hour of auxiliary heat costs far more than an hour of normal heat pump operation.

Why auxiliary heat comes on during cold Panhandle nights

There are four everyday reasons the backup strips kick in:

• Low outdoor temperatures. As the air outside gets colder, there is less heat to pull from it and the heat pump's output drops. On the coldest nights inland, in places like Crestview, Marianna and DeFuniak Springs, the house can lose heat faster than the heat pump can replace it, so the thermostat adds the strips.
• Big jumps on the thermostat. Many thermostats bring on auxiliary heat when the indoor temperature is more than two or three degrees below the setting. Turning the thermostat up five degrees in the morning can trigger the strips even on a mild day.
• Defrost cycles. When frost builds up on the outdoor coil, the heat pump briefly switches to cooling mode to melt it. The strips usually run during defrost so you do not feel cold air from the vents. This is normal and short.
• A problem with the heat pump itself. Low refrigerant, a failed outdoor fan, a stuck reversing valve or a clogged filter can leave the heat pump unable to do its job, and the strips quietly cover for it. You stay warm, but the bill climbs.

How to tell if auxiliary heat is running too much

Most homeowners only find out when the bill arrives. A few simple checks give you an earlier warning:

• Watch the thermostat display on a cold morning. If AUX shows for long stretches when it is not especially cold outside, something is off.
• Compare your daily usage. FPL, CHELCO, Gulf Coast Electric, West Florida Electric, Escambia River Electric and Talquin all offer some form of online usage history for their members or customers. A day with an unusual spike that lines up with a cold night or a thermostat change is a clue.
• Go outside while the system is heating. The outdoor unit should be running and the fan turning. If the indoor blower is pushing warm air but the outdoor unit is silent, the heat may be coming entirely from the strips.
• Look for ice. A thin layer of frost that clears during a defrost cycle is fine. A unit encased in ice that never clears needs service.

Thermostat habits that keep auxiliary heat in check

Thermostat settings make a bigger difference with a heat pump than with almost any other heating system.

• Avoid deep setbacks. Dropping the temperature by six or eight degrees overnight and then cranking it back up in the morning is a common way to force the strips on. With a heat pump, a small setback or none at all is usually cheaper.
• Raise the temperature in small steps. If you want the house warmer, go up one degree at a time and give the heat pump time to catch up.
• Use a thermostat built for heat pumps. Many smart thermostats have a heat pump mode, an outdoor temperature sensor or a setting that limits when auxiliary heat may run. An HVAC technician should set those limits for your specific system, because a lockout set too aggressively can leave the house cold on the hardest nights.
• Leave emergency heat off. Emergency heat is meant for when the heat pump has failed and you are waiting on a repair. Leaving it switched on by mistake can quietly run up a large bill.

Maintenance that helps the heat pump carry the load

The less help the heat pump needs, the less the strips run. Basic upkeep matters:

• Change or clean the air filter on schedule. A clogged filter cuts airflow and makes the system work harder.
• Keep the outdoor unit clear of leaves, pine straw and shrubs. It needs open air on all sides.
• Make sure gutters do not drip directly onto the outdoor unit, which can cause heavy ice in a freeze.
• Have the system checked by a licensed HVAC contractor if it struggles in mild weather, short-cycles, or blows lukewarm air without the strips running.

Leaky ducts in an unconditioned attic and thin attic insulation also let heat escape, which pushes the system toward auxiliary heat sooner. Sealing ducts and topping up insulation help in both winter and summer.

How much does auxiliary heat cost?

The math is simple even if the exact number depends on your system and your utility's rate. Heat strips are rated in kilowatts. A strip rated at 10 kW that runs for one full hour uses 10 kilowatt-hours. Multiply the kilowatt-hours by the price per kWh on your bill and you have the cost of that hour.

The rating of your heat strip is usually printed on the air handler's label or on the strip kit itself. If you know the rating and roughly how many hours the strips ran, you can estimate how much of a high winter bill came from backup heat. A heat pump doing the same job without help would use a fraction of that electricity, which is why cutting down on strip hours is where the savings are.

Where solar fits in a winter heating plan

Solar panels do not change how your heat pump works, but they change what you pay for the electricity it uses. Panhandle homes still get useful winter sun, although the shorter days mean a solar system produces less in December and January than in spring and summer.

For FPL customers, including homes in the former Gulf Power territory, extra solar production that flows back to the grid is credited at the retail rate under net metering. Credits built up in sunnier months can offset part of what you use in winter, subject to FPL's rules on how credits carry over. Co-ops such as CHELCO, Gulf Coast Electric, West Florida Electric, Escambia River Electric and Talquin, and city utilities, set their own net metering rules, so it is worth asking your provider how exports are credited before you size a system.

A home battery is a good fit for keeping a fridge, lights, internet and other essentials running during an outage, but heat strips draw so much power that a battery is not a practical way to run them for long. If backup heat during outages matters to you, it is worth talking through which loads you want covered.

If you are thinking about solar for a home in Niceville, Tallahassee or anywhere else in the region, MSM Solar offers free site surveys and written quotes for new solar installations, with typical pricing of about $3.25 per watt installed. Florida exempts solar equipment from sales tax and excludes the added home value from property tax assessments. The 30% federal residential solar tax credit ended for systems installed after December 31, 2025, so new homeowner installs no longer qualify for it.

Frequently asked questions

Is it bad if my thermostat shows AUX?

Not by itself. Auxiliary heat is supposed to run on very cold nights, during defrost cycles and when you raise the thermostat several degrees. It is a concern when it runs for long periods in mild weather or every time the system heats.

What is the difference between auxiliary heat and emergency heat?

Auxiliary heat comes on automatically alongside the heat pump. Emergency heat is a manual setting that shuts off the heat pump and uses only the electric strips. Use emergency heat only when the heat pump has failed.

Should I turn my heat pump off at night to save money?

Usually not. Large overnight setbacks often trigger auxiliary heat in the morning, which can cost more than holding a steady temperature. A small setback of a degree or two is generally safer.

Can solar panels run my heat pump in winter?

A solar system supplies power to the whole house while the sun is up, including the heat pump. With net metering, credits from sunnier months may help offset winter use, depending on your utility's rules.

Conclusion

MSM Solar works with homeowners in Cantonment, Mary Esther and Mexico Beach, and in every town between Pensacola and Apalachicola.

Auxiliary heat is a useful backup, but it is the most expensive way a heat pump system can warm your home. Keep thermostat changes small, skip deep overnight setbacks, keep the filter and outdoor unit clean, and have a technician look at the system if the AUX light is on more than it should be. If you also want to cut what you pay per kilowatt-hour over the long run, call MSM Solar at (850) 737-5197 for a free site survey and written quote. A real person calls back within 2 business days.