Can a Space Heater Heat a House When Furnace Fails?

When your home’s furnace fails, a space heater can be a temporary solution to keep your house warm. However, it’s important to understand the limitations and safety considerations of using a space heater to heat an entire house. This comprehensive guide will provide you with the technical details and practical advice you need to effectively use a space heater to heat your home when the furnace is not functioning.

Understanding Space Heater Capabilities

Space heaters are designed to heat a single room or small area, not an entire house. The wattage of a space heater determines its heating capacity. Typical space heaters range from 750 watts to 1500 watts, with higher wattage models capable of heating larger spaces.

Wattage Recommended Room Size
750W Up to 150 sq. ft.
1000W 150 to 300 sq. ft.
1500W 300 to 450 sq. ft.

To heat an entire house, you would likely need multiple space heaters, which can quickly become an expensive and energy-intensive solution. Additionally, the heat output of space heaters is localized, meaning they may not effectively distribute warmth throughout the house.

Factors Affecting Space Heater Efficiency

can a space heater heat a house when furnace fails

Several factors can impact the efficiency and effectiveness of using a space heater to heat a house:

  1. Insulation and Weatherproofing: Well-insulated and weatherproofed homes will retain heat better, allowing a space heater to work more efficiently. Homes with poor insulation or drafty windows and doors will require more energy to maintain a comfortable temperature.

  2. Room Size and Layout: Larger rooms or open floor plans will require more powerful space heaters to achieve the desired temperature. Smaller, enclosed spaces are generally easier to heat with a single space heater.

  3. Thermostat Placement: The location of the thermostat can affect the space heater’s ability to accurately monitor and regulate the temperature. Placing the thermostat near the space heater may result in the heater cycling on and off more frequently.

  4. Electricity Costs: The operating cost of a space heater will depend on the local electricity rates. Regions with higher electricity prices will see a more significant impact on their energy bills when using space heaters.

Safety Considerations

Using a space heater to heat a house comes with inherent safety risks that must be addressed. Improper use of space heaters can lead to fires, burns, and other hazards. Follow these safety guidelines when using a space heater:

  • Place the space heater on a level, stable surface, at least 3 feet away from flammable materials.
  • Avoid using extension cords or power strips, as they can overload and pose a fire risk. Plug the space heater directly into a wall outlet.
  • Never leave a space heater unattended or running while sleeping.
  • Keep children and pets away from the space heater to prevent accidental contact and burns.
  • Ensure the space heater has an automatic shut-off feature in case it tips over or overheats.
  • Regularly inspect the space heater for any damage or wear and tear, and replace it if necessary.

Supplementary Heating Options

While a space heater can provide temporary relief when a furnace fails, it may not be the most practical or cost-effective solution for heating an entire house. Consider these additional options:

  1. Portable Propane Heaters: Propane heaters can be a more powerful and efficient alternative to electric space heaters, but they require proper ventilation and safety precautions.

  2. Kerosene Heaters: Kerosene heaters are another portable heating option, but they also require careful handling and ventilation to prevent carbon monoxide poisoning.

  3. Fireplace or Wood Stove: If your home has a functioning fireplace or wood stove, these can be used to supplement the heating provided by a space heater.

  4. Temporary Heating Coils: Some HVAC companies offer emergency heating coils that can be installed to provide temporary heat until the furnace is repaired.

When considering these supplementary heating options, be sure to research the specific safety requirements and energy efficiency of each solution to ensure the best outcome for your home.


While a space heater can be used to heat a house when a furnace fails, it is not the most efficient or cost-effective solution. Space heaters are designed to heat small, localized areas, and using them to heat an entire house can be challenging and potentially unsafe. By understanding the technical specifications, efficiency factors, and safety considerations of using a space heater, you can make an informed decision on the best way to keep your home warm until your furnace is repaired.

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