While central heating is the most common and efficient way to keep your home warm, it may not always be enough, especially in small spaces or in rooms that are not frequently used.

In such cases, using a space heater as a supplemental heating source can be a great option.

However, it is crucial to choose the right size of space heater for your needs.

Factors to Consider When Choosing a Space Heater

Before we dive into the process of determining the appropriate size of space heater, let’s take a look at the factors that need to be considered.

Factors to Consider When Choosing a Space HeaterDescriptions
A. Square footage of the roomThe size of the room that needs to be heated is the most important factor to consider when choosing a space heater. It determines the heating capacity required to maintain a comfortable temperature.
B. Height of the ceilingsRooms with high ceilings require more heating capacity as heat rises and gets trapped at the top. Hence, the height of the ceiling needs to be considered when choosing a space heater.
C. Insulation of the roomThe insulation of the room determines how well the heat is retained. A poorly insulated room will lose heat quickly, requiring a higher heating output to maintain a comfortable temperature.
D. British thermal units (BTUs)BTUs measure the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. The higher the BTUs, the higher the heating capacity of the space heater.
E. Watts per square footWatts per square foot is another measure of the heating capacity required to maintain a comfortable temperature. The standard calculation is 10 watts per square foot, but it can vary based on the insulation, ceiling height, and other factors.
F. Heating outputThe heating output of the space heater determines how much heat it can generate. It is usually measured in watts or BTUs.
G. Type of space heaterDifferent types of space heaters have different heating capacities and output levels. It is important to choose the right type of space heater based on your heating needs.

Below are the recommendations based on our experience in installing various types of heaters over the past several years.

A. Square footage of the room

Room SizeSquare FootageBTUs Required (20 BTUs/sq.ft.)Watts Required (10 watts/sq.ft.)
Small100 sq.ft.2000 BTUs1000 watts
Medium250 sq.ft.5000 BTUs2500 watts
Large500 sq.ft.10000 BTUs5000 watts

B. Height of the ceilings

Ceiling HeightAdditional BTUs Required (25%)
Standard (8 feet)0 BTUs
High (10 feet)25% additional BTUs required
Very High (12 feet or more)50% or more additional BTUs required

C. Insulation of the room

Insulation LevelAdditional Heating Output Required
Poor25-30% additional heating output required
AverageStandard heating output required
Good10-15% less heating output required

D. British thermal units (BTUs)

Room SizeSquare FootageBTUs Required (20 BTUs/sq.ft.)
Small100 sq.ft.2000 BTUs
Medium250 sq.ft.5000 BTUs
Large500 sq.ft.10000 BTUs

E. Watts per square foot

Room SizeSquare FootageWatts Required (10 watts/sq.ft.)
Small100 sq.ft.1000 watts
Medium250 sq.ft.2500 watts
Large500 sq.ft.5000 watts

F. Heating output

Heater TypeHeating Output
Radiant600-1500 watts
Fan-forced1000-1500 watts
Convection500-1500 watts
Oil-filled600-1500 watts

G. Type of space heater

Heater TypeHeating CapacityProsCons
CeramicUp to 1500 wattsQuick heating, energy efficient, quietCan be expensive, high surface temperature
RadiantUp to 1500 wattsDirect heat, no fan noise, energy efficientLimited area coverage, high surface temperature
Oil-filledUp to 1500 wattsEven heating, energy efficient, safeSlow to heat up, heavy and bulky
Fan-forcedUp to 1500 wattsQuick heating, affordable, portableCan be noisy, dries out the air
ConvectionUp to 1500 wattsEven heating, energy efficient, silent operationSlow to heat up, can be bulky

Determining the Appropriate Size of Space Heater

Now that we have covered the factors to consider, let’s move on to the process of determining the appropriate size of space heater for your needs.

Calculation of the square footage of the room

The first step is to measure the square footage of the room that needs to be heated. This can be done by measuring the length and width of the room and multiplying them. For example, if the room is 10 feet by 12 feet, the square footage is 120 square feet.

Calculation of the BTUs required

Once you have the square footage, you can calculate the BTUs required to heat the room. The standard calculation is 20 BTUs per square foot for rooms with standard ceilings (8 feet). For rooms with high ceilings, add an additional 25% to the BTU calculation. Using our example of a 120 square foot room with standard ceilings, the BTUs required would be:

20 BTUs/sq.ft. x 120 sq.ft. = 2400 BTUs

Calculation of the watts per square foot required

Another way to determine the appropriate size of space heater is by calculating the watts per square foot required. As mentioned earlier, the standard calculation is 10 watts per square foot. Using our example of a 120 square foot room, the watts required would be:

10 watts/sq.ft. x 120 sq.ft. = 1200 watts

Comparison of the results to the available heater sizes

Once you have the BTUs and watts per square foot required, you can compare them to the available heater sizes. It is important to choose a heater that meets or exceeds the required heating capacity. For example, if the required heating capacity is 2400 BTUs or 1200 watts, you can choose a 1500-watt space heater or a 2500 BTU space heater.

Selection of the appropriate size of space heater

Based on the above calculations, you can select the appropriate size of space heater for your needs. It is important to note that the size of the room is not the only factor to consider. The height of the ceiling, insulation of the room, and other factors can affect the heating capacity required. Hence, it is always recommended to choose a slightly higher heating capacity than the minimum required.

How to Choose a Space Heater for a Big Room?

Choosing a space heater for a big room requires careful consideration to ensure effective and efficient heating. Let’s explore the essential factors to consider when selecting the ideal space heater for larger spaces.

Calculate the Required Wattage

For a big room, selecting a space heater with sufficient wattage to generate the necessary heat is crucial. Generally, larger rooms require higher-wattage heaters to achieve the desired temperature comfortably. Consider the room’s square footage and the desired temperature rise to calculate the required wattage.

You can use online calculators or consult the manufacturer’s recommendations to determine the ideal wattage for your big room.

Poor insulationAdd 4 watts per square foot
High ceilings (over 8 feet)Add 1 watt per square foot for each extra foot
Large windows or patio doorsAdd 1.5 watts per square foot
Very cold climate (below 20°F)Add 5 watts per square foot
Well insulatedSubtract 4 watts per square foot
Low ceilings (under 8 feet)Subtract 1 watt per square foot for each footless
Small windows or no windowsSubtract 1.5 watts per square foot
Mild climate (above 50°F)Subtract 5 watts per square foot

    I.      Convert Watts into BTUs

Watts is a measure of electrical power. However, some house heaters use different fuels, such as fuel or propane. In that case, you want to convert watts into BTUs (British Thermal Units), a measure of warmth output. One watt equals about 3.41 BTUs. So, to convert watts into BTUs, indeed multiply by 3.41.

For example, if you want a house heater with a wattage of 1800 watts, you would want one with a BTU output of about 6138 BTUs (1800 x 3.41 = 6138).

   II.      How Many Watts per Square Foot?

The rule is that 10 watts of heating electricity per rectangular foot is required for indoor comfort. This is real for insulated space. Suppose you’re attempting to warm storage or a different poorly insulated or non-insulated house with an electric-powered heater. In that case, 10 watts of heating electricity per rectangular foot will no longer do the job.

Choose a Heater with Multiple Heat Settings

Opt for a space heater that offers multiple heat settings, such as low, medium, and high. Different heat settings allow you to adjust the heater’s output according to your room’s heating needs. In milder conditions, you can use the low or medium setting to save energy, while the high setting can provide maximum warmth during colder days.

Look for a Heater with Oscillation

When searching for the perfect space heater, one feature that can significantly enhance its performance, especially in larger rooms, is oscillation. Oscillation refers to the heater’s ability to rotate or swivel, distributing heat in a wide arc across the room. This advantageous characteristic offers several benefits that contribute to a more comfortable and evenly heated environment:

ü Even Heat Distribution:

Oscillation ensures the heat is uniformly dispersed throughout the room. As the heater rotates, it covers a broader area, preventing any concentration of heat in specific spots. This eliminates the formation of uncomfortable hot spots or chilly cold spots, providing a well-balanced and consistent temperature from wall to wall.

ü Enhanced Comfort:

With oscillation, every corner of the room receives sufficient warmth. Occupants no longer need to huddle around a single fixed heat source. Instead, the rotating heater ensures everyone in the room experiences a cozy and comfortable environment, regardless of location.

ü Elimination of Stagnant Air:

In rooms with fixed heaters, stagnant air can accumulate in areas far from the heat source. This can lead to temperature differences and discomfort. Oscillating heaters continually circulate the warm air, preventing the formation of stagnant pockets and creating a more dynamic and enjoyable atmosphere.

ü Reduced Energy Waste:

In the absence of oscillation, some fixed heaters may need to operate at higher power settings to achieve adequate room-wide warmth. This can result in unnecessary energy consumption. With an oscillating heater, the heat is efficiently distributed, enabling lower heat settings and ultimately saving energy.

ü Improved Heat Coverage:

Larger rooms or open spaces often challenge achieving uniform heating. Oscillating heaters address this issue by sweeping the heat back and forth, covering a broader area, and ensuring that even the farthest corners receive ample warmth.

ü Flexible Placement:

Oscillating heaters allow for more flexible placement options. Since the heat is distributed in multiple directions, the heater can be positioned at different room points without compromising efficiency. This adaptability makes it easier to find an optimal location for the heater that complements the room’s layout and occupants’ preferences.

Consider Safety Features

Safety is paramount when using space heaters, especially in bigger rooms with multiple people. Look for heaters with essential safety features, such as tip-over protection, which automatically shuts off the heater if it accidentally tips over. Overheat protection is also essential, as it prevents the heater from becoming too hot and posing a fire hazard.

Heater TypeDescriptionRoom SizeHeating MethodSafety
Fan-forcedUses a fan to blow hot air across a heating elementSmall to MediumFan-forcedDry air, burn risk
ConvectionUtilizes natural air circulation for even heatingLarge or OpenNatural air circulationBurn risk
InfraredEmits infrared rays for spot heatingSmallInfrared radiationSafe to touch
RadiantEmits heat in a specific directionSmall to MediumRadiant heatFire hazard, eye strain
MicathermicCombines convection and radiant heatLargeConvection and radiant heatExpensive, rare


Evaluate the Noise Level

When selecting a space heater for use in larger rooms, one crucial aspect to consider is the unit’s noise level. A noisy heater can considerably distract and hinder productivity in bustling environments where people may be working, studying, or engaging in conversations. Here are key reasons why evaluating the noise level of a space heater is essential for creating a comfortable and focused environment:

ü Minimize Distractions:

A space heater with quiet operation helps minimize distractions, allowing occupants to concentrate on their tasks without being constantly aware of the heater’s noise. This is particularly crucial in offices, study areas, or libraries, where productivity and focus are paramount.

ü Uninterrupted Learning and Working:

In educational settings or workplaces, a noisy heater can disrupt lectures, presentations, or discussions. Opting for a silent heater ensures that learning and work environments remain undisturbed, fostering a conducive atmosphere for active engagement and participation.

ü Enhance Relaxation:

A quiet space heater contributes to a tranquil ambiance in larger rooms where people gather for relaxation or leisure. Whether it’s a living room, lounge area, or recreational space, a serene atmosphere aids in unwinding and unwavering enjoyment of recreational activities.

ü Promote Undisturbed Sleep:

In bedrooms or sleeping areas, the noise level is critical in promoting a restful sleep environment. Quieter space heaters are ideal for maintaining a peaceful atmosphere conducive to a good night’s rest.

ü Considerate for Shared Spaces:

A quiet space heater is considerate of others using the same space in shared living spaces or multifunctional rooms. It allows individuals to carry out their activities without causing disruptions to others who may be engaged in different tasks.

ü Improved Concentration:

Concentration in academic or work settings is vital to absorbing information or completing tasks efficiently. A quiet space heater supports improved concentration as it fades into the background and becomes unobtrusive during essential activities.

ü Preserve peace:

In spaces where people value a calm and tranquil atmosphere, such as meditation rooms, yoga studios, or reading nooks, a noiseless heater maintains the desired peace essential for such activities.

Opt for Energy-Efficient Models

When selecting a space heater for a big room, prioritizing energy efficiency is paramount. A larger space requires more heating power, and inefficient heaters can lead to excessive energy consumption, resulting in higher utility bills. Energy-efficient models maintain a consistent level of warmth without sudden fluctuations. They deliver reliable heating performance, ensuring that you’re living or working space remains comfortable and cozy throughout the day.

Here’s why opting for energy-efficient models is a smart choice for keeping your big room comfortably warm while being mindful of your energy usage:

·      Cost Savings:

Energy-efficient space heaters are designed to provide effective heating performance while minimizing electricity consumption. Choosing an energy-efficient model can significantly reduce heating costs, especially during prolonged use throughout the colder months.

·      Sustainable Heating:

Energy-efficient heaters contribute to a more sustainable and eco-friendly living. These models are engineered to use less energy to achieve the same level of warmth, thereby reducing overall energy demand and decreasing your carbon footprint.

·      Long-Term Investment:

Energy-efficient heaters may have a slightly higher initial cost but offer long-term benefits. Over time, the energy savings can offset the initial investment, making them a cost-effective choice for your big room’s heating needs.

·      Consistent Comfort:

Energy-efficient heaters are designed to maintain a consistent level of warmth without sudden fluctuations or temperature spikes. This ensures that your big room remains comfortably heated throughout the day, providing occupants with a cozy and pleasant environment.

·      Reduced Environmental Impact:

Selecting energy-efficient models helps to save natural resources and lower greenhouse gas emissions. Using less energy to heat your big room helps to achieve the worldwide objective of reducing climate change and protecting the environment for future generations.

·      Efficient Heating Solutions:

Energy-efficient space heaters have advanced heating technologies and intelligent features that optimize their performance. These may include programmable thermostats, timers, and sensors to regulate the temperature and operation based on occupancy, further enhancing energy savings.

·      Certifications and Standards:

Many energy-efficient space heaters carry energy certifications, such as Energy Star ratings, indicating compliance with rigorous efficiency standards. Opting for certified models gives you confidence in their efficiency and performance.

·      Smart Energy Use:

Energy-efficient heaters contribute to smart energy consumption. They are designed to use only the energy necessary to reach and maintain the desired temperature, avoiding unnecessary wastage of electricity.

·      Quiet Operation:

Many energy-efficient space heaters also prioritize quiet operation. This is beneficial in environments where low noise levels are preferred, such as bedrooms, offices, or study areas.

·      Incentives and Rebates:

In some regions, using energy-efficient appliances may make you eligible for incentives, rebates, or tax credits. Check with local authorities or utility companies to explore potential cost-saving opportunities.

By choosing energy-efficient models, you not only enjoy the benefits of a warm and comfortable environment but also contribute to a sustainable future and financial savings. Look for the Energy Star label or other energy certifications when selecting your space heater, and consider its efficiency features to make the most informed and eco-conscious decision for your heating needs.

Common Mistakes When Choosing a Space Heater

Now that we have covered the process of determining the appropriate size of space heater, let’s take a look at some common mistakes to avoid.

Relying solely on the wattage of the heater

Wattage is an important factor to consider when choosing a space heater, but it is not the only factor. The heating capacity required varies based on the size of the room, height of the ceiling, insulation, and other factors.

Also, be extra cautious while using an extension cord for a space heater.

Neglecting the height of the ceilings

As mentioned earlier, rooms with high ceilings require more heating capacity. Neglecting the height of the ceiling can result in a space heater that is too small for the room.

Ignoring the insulation of the room

A poorly insulated room will lose heat quickly, requiring a higher heating capacity to maintain a comfortable temperature. Ignoring the insulation of the room can result in a space heater that is too small for the room.

Usage With Generators

Determine the capacity of your solar generator to understand the amount of power it can provide. Check the wattage or power output of the generator and compare it to the requirements of the space heater you intend to use. Ensure that the generator has sufficient capacity to handle the heater’s power needs without overloading the system.


Choosing the appropriate size of space heater is crucial for maintaining a comfortable temperature in your living spaces. Factors such as the size of the room, height of the ceiling, insulation, and heating output need to be considered when selecting a space heater. By following the above process and avoiding common mistakes, you can choose the right size of space heater for your needs and stay warm and cozy during the chilly weather.