How Big Propane Heater Will I Need?

When it comes to heating your garage or any other space, choosing the right size propane heater is crucial for ensuring efficient and effective heating. The size of the propane heater you need depends on several factors, including the size of the space, insulation, desired temperature rise, and local climate conditions. In this comprehensive guide, we’ll dive deep into the technical details and provide you with a step-by-step approach to determine the perfect propane heater size for your needs.

Calculating the Required BTUs

The first step in determining the size of the propane heater you need is to calculate the required BTUs (British Thermal Units) for your space. This can be done using the following formula:

(Insulation * Cubic Feet of Garage * Temperature Rise) / 1.6 = # of BTU

Let’s break down the components of this formula:

  1. Insulation: The insulation level of your garage or space plays a crucial role in determining the heat loss. The higher the insulation, the lower the heat loss, and the smaller the heater you’ll need. Insulation values typically range from 1 (poor insulation) to 5 (excellent insulation).

  2. Cubic Feet of Garage: This is the volume of the space you need to heat, calculated by multiplying the length, width, and height of the garage or space.

  3. Temperature Rise: This is the desired temperature increase you want to achieve in the space. For example, if the current temperature is 50°F and you want to raise it to 85°F, the temperature rise would be 35°F.

  4. 1.6: This is a constant factor that accounts for the conversion from cubic feet to BTUs.

Let’s consider an example:

Suppose you have a 3,840 cubic feet garage with average insulation (insulation value of 3) and you want to achieve a 35°F temperature rise. Using the formula, the required BTUs would be:

(3 * 3,840 * 35) / 1.6 = 84,000 BTU

This means you would need a propane heater with a minimum of 84,000 BTU to effectively heat your 3,840 cubic feet garage with a 35°F temperature rise.

Considering Local Climate Conditions

how big propane heater will i need

The local climate conditions in your area can significantly impact the size of the propane heater you need. If you live in a region with colder temperatures, you may require a larger heater to compensate for the increased heat loss.

For instance, if you live near Colorado Springs, Colorado, at an elevation of 7,400 feet, you may experience temperatures in the single digits during the winter. In this case, you may need a heater with a higher BTU rating to maintain a comfortable temperature in your garage.

To account for the local climate, you can use the following guidelines:

  • Colder Climates: Add 10-20% to the calculated BTU requirement to compensate for increased heat loss.
  • Warmer Climates: Subtract 10-20% from the calculated BTU requirement, as the heating demand will be lower.

Efficiency Ratings and Heater Selection

When selecting a propane heater, it’s important to consider the heater’s efficiency rating. Propane heaters typically have an efficiency rating between 75% and 95%. A higher efficiency rating means that the heater will convert more of the propane’s energy into heat, resulting in lower fuel costs and a smaller heater size.

To ensure you select the right size heater for your needs, you can use a heater size BTU calculator, such as the one provided by Heat Wagon. This calculator takes into account the size of the space, insulation, and desired temperature rise to determine the required BTU rating for your heater.

When choosing a propane heater, it’s also important to consider the following factors:

  • BTU Output: Ensure the heater’s BTU output matches or exceeds the calculated requirement.
  • Heating Area Coverage: Check the manufacturer’s recommended heating area coverage to ensure the heater can effectively heat your space.
  • Fuel Consumption: Consider the heater’s fuel consumption rate to estimate your ongoing propane costs.
  • Safety Features: Look for propane heaters with safety features like automatic shut-off, tip-over protection, and carbon monoxide detection.


Determining the right size propane heater for your needs is a crucial step in ensuring efficient and effective heating in your garage or any other space. By considering the size of the space, insulation, desired temperature rise, and local climate conditions, you can calculate the required BTUs and select the appropriate propane heater for your needs. Remember to use a heater size BTU calculator and consider the heater’s efficiency rating, heating area coverage, fuel consumption, and safety features to make an informed decision.

In-Depth Outdoors: Garage Heater Size
Heat Wagon: Heater Size BTU Calculator
Danley’s: Garage Heater Guide
Garage Journal: Propane Unit Heater Sizing
Total Home Supply: Heating BTU Calculator