Is It Cheaper to Run a Space Heater or a Furnace

Deciding between running a space heater or a central furnace depends on energy prices, home size, heating needs, and equipment efficiency. This article breaks down the costs, compares energy sources, provides practical examples, and offers actionable tips to save on winter heating bills.

Factor	Space Heater	Furnace
Best Use	Supplemental, single room	Whole-home heating
Typical Efficiency	80%–100% (electric)	70%–98% AFUE (gas/electric)
Operating Cost (Per Hour)	Depends on wattage & electric rate	Depends on fuel type, AFUE, and furnace size
Safety Concerns	Overheat, tip-over	Carbon monoxide, venting
Best For	Room-focused savings	Whole-house comfort

How Heating Costs Are Calculated

Heating cost equals the amount of energy used multiplied by the unit price of that energy, divided by the system efficiency. For electric heaters, energy is measured in kilowatt-hours (kWh). For gas furnaces, energy is measured in therms or cubic feet of natural gas. Efficiency and local utility rates are the two primary levers that determine actual cost.

Key Factors That Affect Cost

Multiple variables influence whether a space heater or furnace is cheaper to run. Understanding them clarifies which option makes sense in specific situations.

Energy Price

Electricity rates vary widely by state and time of day. Natural gas prices also vary seasonally and regionally. Where electricity is inexpensive, electric space heaters may be cost-effective for short periods.

System Efficiency

Space heaters convert nearly all electric energy to heat, giving them close to 100% instantaneous efficiency. Gas furnaces are rated by AFUE (Annual Fuel Utilization Efficiency), typically 80%–98%. Heat pumps offer higher seasonal efficiencies but depend on outdoor temperature.

Heating Area And Distribution

Space heaters concentrate heat in a small zone; furnaces distribute heat through ducts to the entire house. Heating an entire home with a space heater is generally inefficient compared to a furnace.

Insulation And Home Envelope

Homes with poor insulation lose heat faster, increasing run time for any heater. Sealing drafts and adding insulation often yield larger savings than switching heating types.

Usage Pattern

Short, targeted heating sessions favor space heaters. Continuous whole-house heating favors furnaces or heat pumps for lower per-hour costs delivered across all rooms.

Types Of Space Heaters And Their Costs

Space heaters come in multiple designs. Knowing their wattage and intended use helps estimate running costs.

• Convection Heaters: Oil-filled radiators that heat air slowly and retain warmth after cycling off.
• Ceramic/Forced-Air Heaters: Fast heat delivery using a fan; good for quick warming of a room.
• Infrared Heaters: Radiant heat that warms objects and people directly; efficient in drafty spaces.
• Micathermic: Lightweight panels combining convection and radiant heat for quiet operation.

Running cost example: A 1500-watt heater at 1.5 kW running for one hour uses 1.5 kWh. If electricity costs $0.16/kWh, hourly cost = 1.5 kWh × $0.16 = $0.24 per hour.

Furnace Types, Efficiency, And Operating Costs

Furnaces are categorized mainly by fuel type and efficiency rating. AFUE expresses how much fuel energy becomes heat over a season.

• Natural Gas Furnaces: Common in many U.S. regions; AFUE ranges 80%–98%. Lower fuel prices can make gas cheaper for whole-home heating.
• Electric Furnaces: Nearly 100% efficient at the point of use but typically more costly per unit of heat because electricity is pricier than gas.
• Oil Furnaces: Less common, higher maintenance; cost-effectiveness depends on local oil prices.
• Heat Pumps: High efficiency (COP >1), particularly efficient in mild climates or when using cold-climate heat pump models.

Running cost example for a gas furnace: If a furnace with 90% AFUE consumes 1 therm of natural gas (100,000 BTU) and the gas price is $1.20/therm, the useful heat cost per therm effectively is $1.20 / 0.90 = $1.33 for the heat delivered.

Example Comparisons: Typical Scenarios

Quantified examples help illustrate when each option is cheaper.

Scenario A: Heating A Single Room For 4 Hours

Using a 1500W space heater at $0.16/kWh for 4 hours: Cost = 1.5 kW × 4 h × $0.16 = $0.96.

Using central furnace (natural gas) to raise whole-home temperature increases gas consumption across all zones. Furnace cost to warm entire house often far exceeds $0.96 for the same period.

Scenario B: Heating Entire House Overnight

A gas furnace running to maintain 68°F for 12 hours may consume several therms depending on home heat loss. If the furnace uses 2 therms overnight at $1.20/therm and AFUE 90%, delivered heat cost ≈ $2.67.

Using multiple space heaters to replace whole-house heating would require many units consuming much more electricity; this is usually more expensive and less safe.

Energy Efficiency Versus Cost Effectiveness

Efficiency is not the only metric; the cost per unit of heat delivered is what matters. Electric heaters are efficient at converting energy to heat, but electricity often costs more per BTU than natural gas. Heat pumps can deliver more heat per unit of energy, making them the most cost-effective option in many climates.

Safety, Comfort, And Practical Considerations

Cost alone should not drive the decision. Safety and comfort are essential.

• Space Heater Risks: Fire hazard, tip-over accidents, and localized overheating. Use models with tip-over and overheat protection and never leave them unattended.
• Furnace Risks: Carbon monoxide from incomplete combustion, faulty venting, or poor maintenance. Annual inspections and working CO detectors are critical.
• Comfort: Furnaces provide even whole-home warmth; space heaters provide strong local comfort but can create cold spots elsewhere.

Maintenance And Long-Term Cost Factors

Regular maintenance affects operating costs. A well-maintained furnace operates closer to its AFUE rating, reducing fuel waste. Space heaters require minimal maintenance but have shorter lifespans.

Upfront costs matter too: a high-efficiency furnace or a ductless heat pump requires higher initial investment but can dramatically reduce seasonal costs compared to electric resistance heating.

When A Space Heater Is Cheaper

Space heaters are often cheaper when heating one occupied room for short periods, especially if the rest of the house can be kept cooler. Examples include working at a desk, sleeping in one bedroom, or supplementing a cold spot.

When A Furnace Or Heat Pump Is Cheaper

For whole-house heating over longer periods, furnaces or heat pumps typically cost less per delivered BTU, particularly where natural gas is inexpensive or heat pumps perform well in the climate.

Practical Tips To Reduce Heating Costs

• Use programmable thermostats to lower overall runtime and avoid heating empty rooms.
• Zone heating: Lower the thermostat in unused rooms and use a space heater when occupying a single room.
• Improve insulation, seal air leaks, and add weatherstripping around doors and windows.
• Service furnaces annually to maintain AFUE and safety.
• Compare energy prices: calculate cost per BTU for electricity vs gas using local rates.
• Consider replacing old furnaces with high-efficiency models or installing a heat pump if the climate and budget allow.

How To Calculate Your Own Cost Comparison

Steps to compare costs accurately for a specific home:

1. Record local energy prices: $/kWh for electricity and $/therm or $/MMBtu for gas.
2. Estimate heater power or fuel consumption (watts for electric, therms or BTU for gas).
3. Adjust for efficiency: divide energy input cost by efficiency to get delivered heat cost.
4. Estimate hours of operation and multiply to get daily or monthly costs.

Example formula: Electric Heater Hourly Cost = (Watts / 1000) × Electricity Rate ($/kWh).

Frequently Asked Questions

Is Using Multiple Space Heaters More Efficient Than A Furnace?

Using multiple space heaters to simulate whole-home heating is usually less efficient and more costly than a single furnace or heat pump, due to higher electricity prices and safety concerns.

Are Space Heaters Cheaper If Electricity Is Cheap?

Yes, if local electricity rates are low, space heaters can be cost-effective for extended use, but they still may not be practical for whole-house heating.

Do Heat Pumps Make Furnaces Obsolete?

Heat pumps outperform traditional electric resistance and often gas furnaces in efficiency, especially in mild climates. Cold-climate heat pumps also work well in many colder regions, reducing dependence on furnaces.

Key Takeaways

Space heaters are the cheaper option for targeted, short-term heating of a single room. Furnaces or heat pumps are typically cheaper and more practical for whole-home heating over long durations. The most economical choice depends on local energy prices, equipment efficiency, insulation, and usage patterns.

Readers are encouraged to run simple cost calculations using local energy rates and consider insulation improvements or equipment upgrades for the best long-term savings.