For the same house and the same winter, a natural gas furnace costs less to run in Idaho than a heat pump, and electric baseboard costs the most of the three. The gap between gas and a heat pump is smaller than the gap between a heat pump and resistance heat. Running cost is one input among several, though. A missing gas line, a need for cooling, or a furnace with years left can change the call.
The short answer for Idaho
Heating fuels are sold in different units, kilowatt-hours for electricity and cubic feet for gas, so the fair comparison is the cost of one million Btu of heat actually delivered to the house. Using average Idaho residential prices from the U.S. Energy Information Administration (EIA) and ENERGY STAR efficiencies, the computed figures are:
- Natural gas furnace at 97% AFUE: $7.64
- Heat pump at 8.1 HSPF2 (seasonal COP about 2.4): $16.00
- Electric resistance baseboard, 100% efficient: $37.98
The gas furnace is the cheapest to run here, $8.36 less per million Btu than the heat pump. Baseboard sits well above both.
Read these numbers for what they are. They compare fuels on the same unit of delivered heat. They are not a yearly bill, which depends on square footage, insulation and thermostat habits, and they say nothing about what the equipment costs to buy and install. The gas figure rests on the EIA statewide residential average, so a local utility’s current rate is the number to check before you commit.
The heat pump figure also uses the ENERGY STAR minimum for a ducted system, so a unit rated above that minimum would come in under $16.00. Even so, gas starts with a large head start in Idaho. If a gas line already serves the house, the furnace is the cheaper system to run; if it does not, a heat pump is far cheaper to run than baseboard.
What each option costs to run in Idaho
| System | Efficiency used | Cost per million Btu delivered |
|---|---|---|
| Natural gas furnace | 97% AFUE | $7.64 |
| Heat pump | 8.1 HSPF2 (seasonal COP about 2.4) | $16.00 |
| Electric resistance (baseboard) | 100% | $37.98 |
The electricity side of the table uses 12.96 cents per kWh, the average residential price year-to-date through July in the EIA’s Electric Power Monthly (Table 5.6.B). That is a statewide average, and utilities and rate plans differ, so treat it as a basis for comparing fuels rather than as your own rate. The gas side comes from the EIA’s average residential gas price, converted at about 1,037 Btu per cubic foot, while electricity converts at 3,412 Btu per kWh.
Why efficiency counts as much as the fuel price
A kilowatt-hour of electricity is a fixed amount of heat if it runs through a resistance element, which is why baseboard lands at the top of the table despite a moderate power price. A heat pump uses that same kilowatt-hour to move heat in from outdoors, delivering about 2.4 times as much heat as the electricity it consumes over a season. A gas furnace at 97% AFUE turns nearly all of the gas it burns into house heat. Efficiency, can erase a price disadvantage or create one.
That is why the label matters when you shop. ENERGY STAR asks for at least 8.5 HSPF2 from a non-ducted split system but 8.1 from a ducted one. A ductless unit has no duct losses, so it starts ahead and has to be better to earn the same badge. If you are comparing two heat pumps, compare HSPF2 to HSPF2, since SEER2 measures cooling only. The What HSPF2 Measures, and Why Ductless Asks for More article walks through the rating in more detail. Compare units on HSPF2 for heating cost, and never on SEER2.
How cold it gets, and what that does to a heat pump
Boise Air Terminal, the reference station for Idaho, logs about 5,320 heating degree days a year (base 65°F), according to NOAA’s 1991-2020 Climate Normals. Degree days add up, for every day of the year, how far the average temperature sat below 65°F. They turn a climate into a fuel bill: twice the degree days means roughly twice the fuel for the same house. The same station records about 1,045 cooling degree days, so summer asks for real air conditioning too.
The coldest month averages a daily low of 25.4°F at that station. That is a winter that dips below freezing every night in January but does not sit in extreme cold for weeks. One station cannot speak for the whole state, though. A mountain county in Idaho can run far colder than Boise, and the farther north or higher up a home sits, the longer and harder its heating season will be.
The seasonal number hides the cold nights
The $16.00 heat pump figure rests on a seasonal average. In deep cold a heat pump’s efficiency drops, and the unit works harder for each Btu it delivers. Many installations pair it with a backup, either electric resistance strips or a furnace, to carry the coldest nights. In a Boise-type climate, most of the season sits in the range where a modern heat pump does its job well, and the backup covers a small share of hours. In a colder mountain location, the backup runs more, and the real cost drifts upward from the seasonal figure.
How a specific unit behaves as temperatures fall is a separate question from the average, and How Cold Is Too Cold for a Heat Pump covers it. In a low-elevation Idaho home, plan for a heat pump with a backup; in a high or northern one, size the backup carefully and expect it to run more.
What homes in Idaho already heat with
The EIA’s Residential Energy Consumption Survey (RECS) 2020 state tables show 74% of Idaho homes heating with a furnace. By fuel, natural gas serves 61%, electricity 26% and propane 6%. Central heat pumps, steam or hot-water boilers, and fuel oil or kerosene appear in the tables as “not reported”: the estimate existed but was suppressed as unreliable. That is not the same as zero. The survey simply does not publish a figure for them.
Two things follow. First, the typical Idaho house is a ducted house, built with a furnace and, in most cases, a gas connection. These shares describe what was installed, which tells you what fuel was cheap when the homes were built. They are not a recommendation. They are also state shares from a national survey, not a count for your county or street.
Second, the starting point changes the comparison. A home with no gas line is comparing a heat pump with baseboard or propane, and the heat pump wins easily against baseboard. Propane prices are not in the figures here, so ask a local supplier before you compare. A house with a boiler and radiators is a different conversion, since a ducted heat pump would need new ductwork, and a ductless system is the usual alternative. The Ductless or Central comparison lays out that trade-off. For the wider picture of how Idaho homes are heated, see Heating a Home in Idaho. Start from what is already in the house: ducts and a gas line favor the furnace, ducts without gas favor a heat pump, and no ducts point toward ductless.
When the other choice wins
The cheapest fuel does not always make the right system. Four situations tip Idaho homes away from the furnace.
No gas service
If gas does not reach the street, the furnace’s $7.64 is academic. The real comparison becomes a heat pump at $16.00 against baseboard at $37.98, and the heat pump wins clearly. Propane is the other path, and its price must come from a supplier.
You need cooling
With about 1,045 cooling degree days at the reference station, Idaho summers are not optional to cool through. A heat pump heats and cools with one set of equipment, and the ENERGY STAR criteria for air-source heat pumps set a floor of 15.2 SEER2 for cooling. A gas furnace does nothing in July, so you would buy a separate air conditioner as well. If an old cooling unit is failing at the same time as an aging furnace, price both routes. If air conditioning needs replacing anyway, get a heat pump quote alongside the furnace-plus-AC quote before deciding on running cost alone.
Dual fuel and aging equipment
A dual-fuel setup pairs a heat pump with a gas furnace. The heat pump covers the mild stretches of the heating season, and the furnace takes over for the coldest nights, which is a sensible fit for a climate like Boise’s if you want both. It does require a compatible setup and a gas connection.
The other case is simply a working furnace. A system with years of life left costs less to keep than any replacement, whatever the per-Btu figure says. The Repairing a Furnace or Replacing It article helps with that decision.
Common questions
Is a heat pump cheaper to run than baseboard heat in Idaho?
Yes. At average Idaho residential prices, the computed cost is $16.00 per million Btu for a heat pump at 8.1 HSPF2, against $37.98 for electric resistance. Both use electricity at 12.96 cents per kWh, but the heat pump moves heat instead of making it.
Does a heat pump still work through an Idaho winter?
Yes, in the sense that the heat pump keeps running. The coldest month at the Boise reference station averages a low of 25.4°F. Efficiency drops in deep cold, which is why many systems add resistance strips or a furnace for the coldest nights. Higher and more northern parts of the state can run colder than Boise.
Why does ENERGY STAR require 8.5 HSPF2 for ductless and 8.1 for ducted?
A non-ducted system has no duct losses, so it begins with an advantage. ENERGY STAR asks it to be more efficient to earn the same label. These are minimums to qualify, not typical values.
Is the $7.64 or $16.00 figure my yearly heating bill?
No. Those numbers compare fuels on the cost of one million Btu delivered to the house. Your yearly bill depends on house size, insulation, thermostat settings and your own utility rates. The figures also leave out the price of the equipment.