A heater’s size for a particular location might be similar to online clothing purchases.

You may work with the figures based on the sizing charts provided by the manufacturers, but there is no assurance that the real size will fit perfectly.

You won’t know for sure until you actually purchase and use the item.

Fortunately, there are a few additional methods to reduce your risk when it comes to heating, and taking into account some measurably different factors will allow you to make an informed approximation.

Heaters must be the proper size, much like clothing, although they are more like socks than shoes in that a tight fit is often sufficient.

The ideal strategy is to get as knowledgeable as you can about your requirements and objectives, then consult a heating provider or manufacturer for more detailed advice.

How Experts Work

HVAC experts carry out intricate “load” calculations when designing heating systems for complete homes that take local climatic information, the home’s layout and construction type, insulation levels, windows, and doors into account.

Maybe a little alchemy, too.

You’ll take into account some of the same criteria, but on a much more basic level, to determine what size heater you want for just a room or other particular place.

The point is that there are better options available than just sizing a heater based on square footage.

Calculate the Area

Addressing the query What heater size do I need? begins with some simple load estimates and the application of general guidelines.

By dividing the length by the breadth, the room’s area is first calculated.

A room that is 15 feet by 20 feet, for instance, has a 300 square foot size.

Many heater manufacturers base their estimates of heater size only on room area, however using the room volume, expressed in cubic feet, is more accurate.

To get the volume of a space, just multiply the area by the ceiling height; for instance, a 300-square-foot room with a 9-foot ceiling has a volume of 2,700 cubic feet.

Heat Values and Fundamental Size

Wattage is often used to size or grade electric heaters.

The British thermal unit, or BTU, is used to grade gas-fueled heaters (including those that run on propane, natural gas, and kerosene).

In terms of science, a BTU is the amount of heat energy needed to raise the temperature of one pound of water by one degree Fahrenheit.

Of fact, calculating your heater size in terms of water weight is like trying to cook with a plumb bob.

So let’s consider that in context.

A very simple industrial rule of thumb is that each square foot of room size requires 10 watts of electric heat.

Therefore, a 3,000-watt electric heater is required in the 300 square foot area.

By multiplying by 3.41, you may easily convert watts to BTUs: 3,000 x 3.41 = 10,230 BTUs.

Other Elements

You may determine the size of heater you need by using the equations mentioned above as a starting point.

A more precise estimate will result from a few more considerations.

This extra information may be used by a qualified salesperson or installer to provide size suggestions, and some manufacturers include sizing charts that call for more information than just square footage information.

Finding the temperature differential, or “heat rise,” between the inside and outdoor spaces is one way to calculate a load more simply.

Find the difference between the target room temperature (let’s say 72 degrees F) and the lowest average temperature for your location to obtain a ballpark approximation (just enter your city on any weather site; for example, in Kansas City the average coldest day is about 22 degrees).

To achieve 50 degrees, subtract 22 from 72.

On the coldest day of the year, you’ll need this heat increase to keep your space cozy.

Additional things to think about are:

  • The volume of the space was calculated using the ceiling height.
  • The quantity and nature of the windows and doors (and how often the doors are opened)
  • Degrees of room insulation.

In plain English, you need a larger heater if there are more windows and doors.

The same holds true if the room has weak or no insulation.

Be careful to talk about window size and location with your heater provider since even the finest windows have relatively poor insulation values when compared to a typical wall assembly.

This may have an impact on anything from the kind of heater that is advised to the size, location, and number of heaters that are required.

Primary or Addition?

The debate about main vs.

supplementary heat is one more thing to take into account.

The primary source of heat in a room is often its only source.

When the main heat source isn’t nearly enough, supplemental heat might assist boost the temperature.

Look at how warm the space becomes with the main heating source to determine how much warmer you want the supplementary heating to be.

If the primary heating system maintains a temperature of 65 degrees throughout the coldest months of the year, you may wish to use a backup heater to raise it by 12 degrees.

When you contact a heating contractor, make important to describe your temperature targets (the 12-degree heat increase) in addition to the room size and potential heat loss factors (windows, doors, inadequate insulation, etc.).

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Written by Bob Matsuoka
Bob Matsuoka is a blogger and founder of RVing Beginner blog. He has been blogging for over five years, writing about his own family’s RV adventures, tips for people who are interested in buying an RV or taking their family on an adventure by RV.