What Size Electric Heater Do I Need

What Size Electric Heater Do I Need? Staying Warm and Cosy

Last Updated on January 10, 2023

While an electric heater warms up a room in a matter of minutes, using the wrong size of electric heater might be quite inconvenient for you. If you use a large electrical heater in a small room, your electricity bills might spike unnecessarily. On the other hand, an electric heater that has a small wattage rating is not suitable for large rooms.

With the right size electric heater, you can easily regulate the temperature of a certain room. So, let’s settle the question that you might have been asking yourself ‘what size electric heater do I need?’.

Since heaters come in various sizes, it might be quite hard to choose the best heater for your room. Not to mention, most heaters have different performances.

In this guide, we are going to show you how to choose the most suitable electric heater for your bedroom, living room, or study. We are also going to take you through various calculations that might help you determine what size of electric radiator that you might need. Let’s get right into it.


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Terminologies You Need to Be Familiar With While Choosing an Electric Heater

Before we get into the nitty-gritty details, let’s take a look at the different terms that you should be familiar with while choosing electric heaters. These are some of the most common terms that you might come across as you are looking for electric radiators:


This is the electrical power of an electric heater. Heaters that have a high wattage rating are more powerful than heaters that have a low wattage rating.


This is a unit that shows you the degree of thermal resistance of a certain product. Think of it as the measure of the insulation properties of a certain object. An object that has a high R-value insulates heat better than an object that has a low R-value.

Temperature Rise

A temperature rise is the difference between the current temperature in a room and the preferred one. It makes it easier for you to determine the amount of energy that is needed to raise the temperature of a room to a certain degree.

Estimating the Electric Heater Size

To maximise the heating capacity of your electric radiator, take into consideration the following factors:

Room Size – Width and Length

an attic room with a heating deviceKnowing the size of a room in your home makes it easier for you to estimate the size of the electric radiator that you might need.

To determine the size of a room in your home, measure the width and length of that room with a tape measure. Once you have measured the room dimensions, multiply those two measurements to come up with the area of the room.

Assuming that 10W heats up one square foot, use the dimensions that you had measured earlier to determine the electrical power that is needed to warm a room.

For instance, if your bedroom is 10 feet long and 10 feet wide, then you will need 1000W to heat up that space. To get the total amount of electrical power required, you just have to multiply the total area of the room by 10.

Ceiling Height

Some electric radiators have various mechanisms that warm air through convection currents.

Warm air rises up to the upper part of a room and displaces cold air to the bottom part of a room. The displaced air gets heated and rises to the top part of a room once it is warm enough. The cycle repeats itself until a uniform temperature is attained in a room.

Ceilings might also affect the performance of an electric radiator. An electric radiator might require more electrical power to warm a room with a high ceiling as compared to a room with a low ceiling.

Measure the height of the ceiling to determine the amount of electrical power that might be required to warm a whole room. For every two feet that you measure, increase the total wattage by 25%.


The number of windows in a certain room might affect the performance of electric radiators and panel heaters. Well, windows might absorb some of the heat energy that is produced by electric radiators. Once they absorb heat energy, they might emit it to the external environment in different ways. In short, windows have poor insulation and might get in your way as you are heating a room.

Unlike walls, windows might cause a temperature drop in a room. If your windows absorb and emit a lot of heat, opt for a heater that has a high wattage rating. On the other hand, if your windows don’t absorb a lot of heat, go for an electrical heater with a low wattage rating. Knowing the average insulation might also help you find the best radiators for your room. It makes it easier for you to add poor insulation watts to the total wattage.

Outside Temperature

Most rooms lose heat energy to the outside environment. In short, most rooms are not 100% energy efficient. Due to this, you have to consider the exterior temperatures while looking for an electrical radiator.

Heat losses are higher in cold environments than in warm environments. For example, a house located in the Arctic will have higher heat losses than a beach house that is located in the Bahamas. If you live in an area that is extremely cold, increase the total wattage of your electric radiator.

Finishing Thoughts

And there you have it. Everything you need to know to answer the question “what size electric heater do I need?”. Since electric heaters come in different sizes, you can easily find the right one for your home or office.

With the right size of the device, heating certain areas become quite easy for you. You can also use a radiator wattage calculator to determine the maximum amount of wattage that is required for a specific space.

Some of the factors that you should also take into consideration while looking for a heater include the size of the room and the height of a ceiling. Once you take those factors into consideration, you can easily find the right heater for your home.

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