Space Heaters Compared to Central Heating

Homeowners often wonder whether it is cheaper to run a small electric space heater in a single room or to operate the home’s central heating system. The answer hinges on how much energy each method consumes and the cost of the energy source. Electric space heaters convert electricity directly into heat, with virtually all the electrical energy becoming thermal energy. Central heating systems, typically powered by natural gas, oil, or electricity, distribute heat throughout the entire house even if only one room is occupied. This calculator allows you to compare the cost of heating a space with a plug-in electric heater against the cost of running a gas furnace for a comparable time period. By entering the heater wattage, the number of hours you plan to run it, and your electricity rate, you can estimate the daily and monthly operating cost of the space heater. For the furnace, the tool asks for its heat output in British thermal units (BTU) per hour, the efficiency rating, the price of natural gas per therm, and the expected operating hours per day. Using these inputs, the calculator determines the fuel consumption and overall cost of each heating method.

The space heater calculation is straightforward. Electrical energy consumed per day is $\mathrm{E\_s}=W\mathrm{h\_s}/1000$ kilowatt-hours, where $W$ is the heater’s wattage and $\mathrm{h\_s}$ the hours of use. The daily cost is $\mathrm{C\_s}=\mathrm{E\_s}\mathrm{r\_e}$, with $\mathrm{r\_e}$ representing the electricity rate. For example, a 1,500-watt heater used six hours a day at $0.15 per kWh consumes 9 kWh and costs $1.35 per day.

Central heating requires a little more math. Furnaces are rated by the heat they deliver to the home, measured in BTU per hour. A furnace with a 60,000 BTU/hr output and 85% efficiency actually burns more fuel than its output suggests. The amount of natural gas consumed per hour is $Q=\mathrm{BTU}/(\eta \times 100,000)$ therms, where $\eta$ is efficiency and 100,000 BTU equals one therm. If the gas price is $\mathrm{r\_g}$ dollars per therm, the hourly cost is $\mathrm{Q\; r\_g}$ and the daily cost is $\mathrm{C\_f}=\mathrm{Q\; r\_g\; h\_f}$, where $\mathrm{h\_f}$ is hours of operation per day. In our example, the furnace burns about 0.705 therms per hour. At $1.20 per therm and eight hours of operation, the daily cost is roughly $6.77.

The comparison highlights why many households selectively use space heaters. Heating only one room with a modest electric device for a limited time can be far cheaper than running a whole-house furnace. Yet, space heaters have limitations. They are most effective for localized or supplemental heating and may not adequately warm large or poorly insulated areas. Safety is also a concern; space heaters should be kept away from flammable materials and never left unattended. Central heating systems, though more expensive to operate for small heating needs, provide consistent temperatures throughout the home and often improve air circulation when paired with ductwork and filtration.

Table 1 illustrates sample scenarios to show how costs scale:

These values assume the default settings in the form. They show that the central furnace quickly becomes expensive when operated many hours per day, while the space heater remains relatively economical. However, relying solely on space heaters to heat a whole house would require multiple units and potentially increase electricity bills dramatically. The break-even point depends on the size of the space being heated and the efficiency of the furnace. When natural gas prices are low or when multiple rooms need heating, the furnace may still be the better choice.

In addition to cost, comfort should influence your decision. Space heaters can create hotspots and leave adjacent areas chilly, whereas central heating provides even warmth. Modern furnaces often integrate with smart thermostats that learn household schedules and optimize performance. Insulation quality, window sealing, and thermostat settings all affect heating requirements. Improving these aspects may yield bigger savings than switching heating methods. Always consider the total energy footprint: electricity generation may emit more carbon in regions with coal-heavy grids, while natural gas combustion releases greenhouse gases directly at the home. Incorporating these environmental costs into decision-making can drive sustainable choices.

Finally, remember that both strategies can coexist. Many households keep their central thermostat slightly lower and use a space heater in the room they occupy most, striking a balance between comfort and cost. This calculator encourages experimentation by letting you adjust variables such as hours of use or energy prices. Revisit it each season as utility rates change and as your schedule shifts. Knowing the numbers makes it easier to tailor heating habits that keep you warm without burning through your budget.