Illinois Heating

Heat pump vs furnace in DeKalb County, Illinois

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Which costs less to run in DeKalb County?

An outdoor air conditioning condenser unit with a top-mounted fan sits on a concrete pad beside a dark blue horizontal lap siding wall with an electrical disconnect box above it, photographed at night.

Heat pump

To heat your home here$2.12per 100,000 Btu

A beige sheet-metal furnace stands on a concrete basement floor against a dark blue painted block wall, with galvanized flue ducts rising to the ceiling and a flexible metal conduit and PVC pipe at its left side.

Furnace

To heat your home here$1.33per 100,000 Btu

At Illinois's gas and electricity prices, a gas furnace makes the same heat as a heat pump for at least 37% less.

Btu stands for British thermal unit, the standard measure of heat energy.

Where does a heat pump shine?

  • Heats and cools in one system

    A heat pump runs the same way all year. It pulls heat into the house in winter and pushes it out in summer.

    A living room with a light gray sofa holding navy and pale blue pillows and a navy fringed throw, a rustic wood coffee table with a woven tray and hydrangeas in a white vase, a navy built-in bookshelf at left, and large windows showing green trees and flowering shrubs.

  • No gas line, nothing burning in the house

    A heat pump runs on electricity alone. Nothing burns inside the house.

    Kitchen interior with a navy island topped by a wood counter and black induction hob holding a pale blue kettle, cream wall cabinets with a built-in black double oven, glass pendant lights, a vase of blue hydrangeas, and glass doors showing a fenced garden.

  • Steady, even comfort

    A heat pump runs long and low instead of blasting on and off. Rooms hold an even temperature all day.

    A dark blue armchair with an open book and gray fringed throw sits beside a lit fireplace and a lamp-topped side table, with a golden-colored dog curled asleep on a patterned rug and snowy trees beyond the window.

Where does a furnace shine?

  • Strong, steady heat in hard cold

    Winter nights here average 17°F, and a furnace keeps putting out hot air the whole time, no matter how low it gets outside. You won't notice it working any harder on the coldest night of the year than on a mild one.

    A two-story dark blue house with white trim and lit windows at dusk, with snow on the roof and ground and a shoveled path lined with small lanterns leading to the front door.

  • Runs on the gas most homes here already use

    Most homes in DeKalb County already have gas service, with utility gas heating 71.6% of them. If that's you, a furnace just uses the line that's already run to your house.

    A row of wood-sided houses with covered porches, stone columns and an exterior gas meter along a snow-covered street, with a person in dark clothing walking on the sidewalk in the distance.

  • Fast, strong heat on demand

    Turn the heat up and the furnace answers right away. There's no long wait for the house to catch up.

    An entryway with a navy glass-paned door showing snow outside, snow-dusted boots on a woven jute rug, a wooden bench with a steaming blue mug, sheer curtains by a window, and a floor vent in the slate tile.

What the cold actually does to a heat pump here

Winter is the long season here, eight months of it, October through May, and the overnight low averages 17°F across December, January and February. That number matters because a standard heat pump starts losing ground well above it. Below 40°F it puts out less heat than its rating says. Below about 35°F it typically needs backup heat to make up the difference. Here, the average winter night is already below both marks.

It gets more specific than that. About 140 nights a year in DeKalb County fall at or below freezing, over half of all the nights the heat runs. Every one of those nights sits below the 35°F and 40°F marks. So this is not a cold snap a heat pump has to get through once or twice a winter. It is most of the season.

The deep cold is the smaller piece of the problem. Only about 13 nights a year drop to 0°F or below. A cold climate heat pump, the kind built and tested to the ENERGY STAR Cold Climate standard, is required to still make 1.75 units of heat per unit of electricity at 5°F and hold on to 70 percent of its warm weather capacity at that temperature. Field tests of prototype cold climate models back this up in practice: backup heat covered only a small share of the output between 0°F and 35°F, and the system running on backup alone was rare even above 0°F. A standard heat pump, the kind built to the federal minimum, was not built for this and was not tested to it.

A furnace does not have this problem. It is sized to make its full rated heat regardless of what the thermometer says outside, so a night at 17°F asks nothing extra of it that a night at 35°F didn't already ask.

A two-story navy blue house with white trim, a small columned front porch and light blue front door, with a shoveled concrete walkway leading across a snow-covered front yard and bare trees overhead.

What it costs, and what to weigh against that

Run the two side by side on price alone and the furnace wins. A gas furnace built to the federal minimum makes the same heat for $1.33 per 100,000 Btu, against $2.12 for a heat pump built to the same minimum standard, at Illinois's average fuel prices. That is gas at $10.64 per million Btu against electricity at $46.51. The heat pump's number assumes no backup heat is used, which, given everything above, is optimistic for a standard model here.

This lines up with what the county already runs on. Utility gas heats 71.6% of homes here, close to three in four. Electricity heats 21.7%, about one in five. That is not a trend reversing itself, it is the baseline a furnace fits into and a heat pump would have to argue against on cost and on cold weather performance both.

A heat pump's case is not about winter. It is about summer, and about having one system instead of two. It heats and cools, so it replaces a furnace and a separate air conditioner with one piece of equipment, no gas line, nothing burning in the house. Summers here run about three months, June through August, with afternoons averaging 82°F, well inside what any heat pump handles as an air conditioner without trouble. A furnace has no answer for cooling at all. It does one job and stops for four months a year.

So the choice comes down to what matters more for this house: the lowest running cost through the long cold season, which favors a furnace paired with a separate air conditioner, or one system that handles both seasons, which favors a heat pump, ideally a cold climate model given how often this county sits below the point where a standard one struggles.

Sources: NOAA nClimDiv · NOAA 1991–2020 seasonal normals · EIA SEDS 2024 · 10 CFR 430.32 · PNNL Building America guide · PNNL-37127 field study · ENERGY STAR product criteria · Census ACS 2020–2024

A blue house entrance with a window-topped door, white trim and light blue railings, concrete steps partly covered in snow, a snow shovel leaning near the door, and snow-laden shrubs on both sides.

Common questions about heat pumps and furnaces

  • Can a heat pump heat a house through an Illinois winter?

    Yes, but not at full strength on its own through the whole winter. A standard heat pump's output falls below its rating once it's under 40°F outside, and DeKalb County's winter overnight low averages 17°F, with about 140 nights a year at or below freezing. A cold climate model holds up much better, keeping at least 70 percent of its 47°F capacity down to 5°F, but either way most homes here pair it with backup heat for the coldest nights.

  • Do I need backup heat with a heat pump here?

    For most homes, yes. A standard heat pump often needs backup heat once it's below about 35°F outside, and DeKalb County's average overnight low in winter is 17°F, with 13 nights a year reaching 0°F or below. Field testing on cold climate heat pumps found backup heat only carries a small share of the load between 0°F and 35°F, and running on backup alone is rare above 0°F, so the need is real but it isn't constant.

  • Can I keep my furnace and add a heat pump?

    Yes, and here that pairing has a real job to do. A heat pump can carry the heat down to around 35°F before it struggles, then the furnace takes over for the harder cold, and DeKalb County sees about 140 nights a year at or below freezing. You get the furnace's full output on the 13 or so nights that hit 0°F, and the heat pump running the milder stretches in between.

  • Is a heat pump cheaper to run than a furnace in DeKalb County?

    No, a furnace costs less to run here. Heating this house with a heat pump runs $2.12 per 100,000 Btu against $1.33 for a gas furnace, both at Illinois's average fuel prices. That gap doesn't include the backup heat a heat pump often needs on the colder nights, which would add to its number.

A gloved worker in dark blue coveralls kneels beside a gray outdoor heat pump unit on a concrete pad, connecting insulated copper refrigerant lines to brass service valves, with pliers and a cordless drill lying on gravel in the foreground.

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