Why is my power bill so high this winter?

Start by separating two different problems

A winter bill that jumps is almost always a mix of two things, and they have completely different answers:

1. The price of electricity went up, or you simply used more of it because it was colder. Nothing is wrong. Nothing to fix.
2. Your system used more electricity than it needed to for the heat it delivered. That is a fault, and it is usually a cheap one to correct.

Most people jump straight to the second and start worrying about a failing compressor. Most of the time it is a configuration problem, not a dying system. But it is worth knowing which you are dealing with before you panic or spend money.

What has actually happened to rates

Being straight with you: some of the increase is not your heat pump.

Duke Energy Carolinas has been stepping residential rates up under a multi-year plan approved back in 2024, with increases landing in each of the following years. On top of that, a further rate settlement was reached in 2026 and is sitting with the North Carolina Utilities Commission — if approved, those rates take effect in January 2027.

So a bill that looks higher than last January may be higher partly because the rate behind it is. That is worth checking before you assume the equipment failed. Pull up last winter's bill and compare the rate per kilowatt-hour, not just the total. If the rate rose and your kilowatt-hours are flat, your system is fine.

You can look up your current rate, see which rate schedule you are on, and check what is changing at Duke Energy — signing in to your account there also gets you the daily usage graph we use below. We are not affiliated with Duke Energy; we just end up explaining their bills a lot.

The big one: electric backup heat

If your kilowatt-hours really did jump, this is where the money usually went.

A heat pump moves heat rather than making it, which is why it delivers roughly two to three units of heat for every unit of electricity it consumes. The electric resistance strips in your air handler — the backup — deliver exactly one. Same heat, two to three times the cost.

Those strips are supposed to come on occasionally, on the coldest nights, alongside the heat pump. When something is wrong, they run far more than that, and the arithmetic gets ugly fast.

A 10 kW strip bank draws about 10 kilowatt-hours for every hour it runs. At roughly fifteen cents a kilowatt-hour, that is about $1.50 an hour. Four hours a day for a month is around 1,200 kWh, or $180 on top of what the heat pump itself used. Larger strip banks and colder months push it higher. That is the bill people cannot explain.

Why the strips run when they shouldn't

• Emergency heat was left on. Someone switched it over during a cold snap and never switched it back. The heat pump is now sitting idle while the strips heat the entire house.
• The thermostat stages badly. A basic builder-grade thermostat will fire the strips any time the room is more than a couple of degrees from setpoint — including every morning if you set the temperature back overnight.
• No auxiliary heat lockout is set. A properly configured system will not allow strips above a chosen outdoor temperature. Plenty of systems have never had that set at all.
• The refrigerant charge is low. A heat pump even slightly undercharged loses a large share of its cold-weather capacity, so it falls behind and the strips fill the gap. Silently, all winter.
• A failed defrost board or stuck reversing valve. The heat pump cannot do its job, so the backup does it instead — that is heat pump repair territory, not a thermostat problem.
• The system is undersized or badly sized for the house and its elevation. Up here that matters more than most places — cold air drains into the coves overnight, and a house in a hollow sees a different winter than one on the ridge above it. It is why we size against a real load calculation on every system replacement, and why the picture differs between Black Mountain and Hendersonville.

Check emergency heat first. Right now.

This takes fifteen seconds and it is the most common single cause we find.

Look at your thermostat. If it says EM HEAT, Emergency Heat, or Aux Heat as the mode rather than a temporary indicator light, switch it back to Heat. Emergency heat exists for exactly one situation: the outdoor unit has failed and you need warmth until someone gets there. It is not a cold-weather setting — our heat pump page explains the difference between auxiliary and emergency heat in full. A house running on emergency heat for a month will produce a bill that looks like a system failure, because in cost terms it is one.

Those same strips are the reason sizing a generator around a heat pump is harder than it looks.

Your thermostat is a more likely culprit than your equipment

Deep overnight setbacks save real money on a gas furnace. On a heat pump they frequently cost money, because recovering four or five degrees in a hurry is exactly what triggers the strips. You bank savings overnight and spend them with interest at 6 a.m.

On a heat pump, keep setbacks to about two degrees, or pick a temperature and leave it there. We went through the detail, including what to look for in a smart thermostat, in the thermostat settings that actually lower your bill.

What else quietly raises the bill

• A loaded filter. Restricted airflow makes everything work harder and longer. Wood heat and pollen load filters far faster than the box suggests — see how often to really change your filter.
• Duct leakage. Ductwork running through an attic or crawl space commonly loses twenty to thirty percent of what passes through it. You are paying to heat the crawl space. Duct sealing fixes efficiency and air quality in the same stroke.
• A dirty outdoor coil or leaves packed against the unit, choking the airflow it needs to pull heat from.
• Space heaters. A 1,500 watt heater is pure resistance heat, the most expensive warmth there is. If a room needs one every winter, that room has a problem worth solving — often a ductless head rather than a space heater forever.
• Everything else electric. Longer nights, more lights, more cooking, guests over the holidays, a hot tub. It is worth ruling out before blaming the HVAC.

How to work it out yourself in twenty minutes

1. Check the thermostat mode. Emergency heat off, fan on AUTO.
2. Compare kWh, not dollars, against the same month last year.
3. Open your utility's daily usage graph. Duke Energy shows usage by day and often by hour once you sign in to your account. Line it up against the weather. Usage that tracks the cold is normal. A flat, permanently high baseline that does not fall when it warms up points at something stuck on.
4. Hold a filter up to the light. If you cannot see through it, that is your first fix.
5. Walk out to the outdoor unit on a cold day. It should be running, and warm air should be coming off the top. If it is sitting dead still while the house is calling for heat, the strips are carrying the whole load. Our guide to getting a heat pump ready for a mountain winter covers the rest of the walk-around.
6. Put your hand in a supply vent. Heat pump air runs about 95–105°F — warm, not hot. Air that is noticeably hotter than that usually means strips are running.

When to call us

• Auxiliary or emergency heat is on for days in ordinary cold
• The outdoor unit is not running when the house is calling for heat
• Usage stays high even when the weather turns mild
• The system runs constantly and still never reaches the thermostat setting
• Ice on the outdoor unit that does not clear within a few hours
• Your bill jumped and nothing above explains it

Book a diagnostic visit and it is usually a short one. We check the refrigerant charge against actual conditions, measure what the strips are drawing and how they stage, confirm the defrost cycle and reversing valve, read static pressure, and go through the thermostat configuration — including setting an auxiliary heat lockout if nobody ever did. More often than not the fix is a setting or a cheap part, not a new system.

And because this is the kind of thing that is invisible until the bill arrives, it is exactly what a twice-yearly check is for. Our maintenance plans cover charge verification, strip amperage and staging, and the thermostat setup, before the cold finds the problem for you.