The Ecobee Display Said Aux Heat for 213 Hours. The Thermostat Was Never the Problem.

I manage procurement and facilities for a 42-person advisory firm. Since 2018, I have kept every utility invoice in a spreadsheet that my coworkers describe as “borderline obsessive.” That spreadsheet paid off in January 2024, when our electricity bill came in $317 higher than the same billing cycle in 2023. The ecobee thermostat on the main floor kept displaying aux heat. My first assumption was that the thermostat had failed. That assumption was wrong, and I want to walk through what actually was going on.

I spent two nights reading ecobee smart thermostat reviews looking for someone with the same symptom. I found plenty. “It runs aux heat all the time.” “The bill went up after installation.” What I did not find in the reviews was the cause. That cause lived in the installer settings, the humidifier, and one surprising electric load in the break room.

Aux Heat Is Backup Heat, Not a Mode to Live In

On an all-electric heat pump system, auxiliary heat usually means resistance heat strips in the air handler. Think of them as space heaters built into the ductwork. They work, but they are expensive. A heat pump moves heat from outside; resistance strips create heat by passing electricity through coils. Depending on outdoor temperature and equipment, a heat pump can deliver two or three times more heat per kilowatt-hour than resistance heat. That is why auxiliary heat should cover gaps in extreme conditions, not lead the daily routine.

In our system, the air handler had two 5kW heat strips. The ecobee run-time report logged 213 hours of auxiliary heat in January 2024. If a single 5kW strip ran every one of those hours, that is 1,065kWh. At our all-in rate of $0.149 per kilowatt-hour—which includes delivery and demand charges—that is about $159. If both strips ran, it is roughly $317. I do not know from the log whether both stages fired during every logged hour. I do not need to know. The point is that aux heat was no longer a backup. It had become a line item.

The Real Culprit Was in the Threshold Settings

The aux heat was not running because the office was freezing. It was running because the configuration gave it permission. The installer had left conservative thresholds, and our schedule made matters worse. The ecobee was allowed to call aux heat during fast temperature recovery. With a 6 p.m. setback and a 6 a.m. recovery, the indoor temperature had to make up a large gap every morning. The thermostat was not trying to sabotage the budget. It was doing exactly what it had been told.

Our previous HVAC technician had suggested adjusting those thresholds during a maintenance visit. I did not approve it because I was trying to hold the visit to a fixed quote. That decision probably cost us far more than the adjustment would have. When the next technician looked at the settings, he changed them and left notes in the control panel. The fix did not require new hardware.

The Ecobee Thermostat Aux Heat Label Is a Symptom, Not a Diagnosis

I want to say this carefully because it matters for anyone searching “ecobee thermostat aux heat”: the label on the screen is not the whole story. The screen was telling the truth in our case. Aux heat was running. The useful question was why. That question led to the thresholds, the schedule, and then to a winter comfort problem that had nothing to do with the thermostat.

The Humidifier Question Was Really an Energy Question

Dry air was making the setpoint creep upward. On dry winter days, our office relative humidity sat near 20 percent. Twenty percent feels dry. People did what people do: they turned the thermostat up. The setpoint drifted from 70°F to 72°F over a few weeks. We did not need warmer air as much as we needed moisture.

This is where I learned something about the question people type into search engines. Our office manager asked me what to fill the humidifier with. I assumed the answer was obvious. It was not. The search version of her question is “what do you put in humidifier,” and it deserves a more direct answer. A portable ultrasonic humidifier should get distilled water if the local tap water has minerals; tap water can create white dust. A whole-home bypass humidifier connected to the HVAC system is a different setup, with a water line and a pad that needs replacement. In both cases, the starting point is plain water. Fragrance or essential oils do not belong in the unit unless the manufacturer explicitly allows them.

Why does this belong in an energy audit? Because a humidifier that is poorly maintained or filled with the wrong water will fail exactly when it is needed. The dry-air complaint returns, and the thermostat setpoint creeps back up. A humidifier is a comfort machine, but it is also a check on how much heat the building needs.

The Break Room Had a Mini Resistance Heater Too

Once I started looking for resistance heat, I found it in places I had not expected. Our office manager bought a Power XL Vortex Pro Air Fryer for the break room. It is not a bad product, and it makes decent frozen fries. But a countertop air fryer is basically a small electric oven with a fan. Like most full-size countertop air fryers, it pulls around 1,500 watts when running. That makes it an electric resistance load, just like a heat strip.

At lunch, when the HVAC system was already working, that load added to the building peak. During the cooling season, the air conditioner had to remove the heat the air fryer created. That is not a reason to ban it. It is a reason to put high-wattage appliances in the same mental category as aux heat. Small products with heating elements are not free to run just because they are small.

I Was Ready to Approve the Jackson Energy Smart Hub Quote

When the January bill first spiked, our utility supplier sent over an energy-management proposal. It listed the Jackson Energy Smart Hub as an option, and I almost approved it. I wanted visibility, and this promised more of it. Looking back, I think the hub would have been useful in a different building. To be fair, I can only speak to our building, not every device on the market. Our problem was not a shortage of data. The data already existed in the ecobee run-time report and the utility interval meter. The gap was a configuration setting. Another dashboard would have made the problem more visible without changing the thresholds.

What I Would Do Differently

If you are seeing aux heat on an ecobee and the energy bill is climbing, start before you buy. Pull the run-time report. Ask your HVAC contractor to review the aux heat and compressor thresholds. Look at the night setback and morning recovery. If dry-air complaints are part of the picture, fix the humidifier and maintain it with the right water. Then look at the rest of the resistance load.

In our case, the expensive fix was not expensive. It was settings, a schedule adjustment, and a humidifier that actually worked. The final lesson was simpler: a thermostat is a control device, not a magic device. And a contractor who treats a small commercial account seriously is worth more than another gadget on the network.

That $317 spike taught me not to blame the interface on the wall. I still like the ecobee. I like it more now that the settings match the building. But no smart device can fix a commissioning gap by itself. The technician who checks thresholds, the office manager who asks about humidifier water, and even the person who plugs in an air fryer all shape the bill. When a smart product causes a mysterious increase, look first at what it is allowed to do.