How to Size a Solar Air Heating System: Practical Tips.

To size a solar air heating system, you need to calculate the amount of energy needed to heat the designated space and the amount of energy the solar panels can produce. The size of the system is determined by the ratio between the two values.

Solar air heating systems are an excellent way to reduce energy usage and save money on heating expenses. The primary purpose of these systems is to absorb sunlight and convert it into heat that can be used to heat a specific area.

However, sizing these systems can be a complex task that requires knowledge of the energy requirements of the space being heated and the amount of energy the solar panels can produce. In this article, we’ll discuss the factors that need to be considered when sizing a solar air heating system to help you make an informed decision about which system is right for you.

How to Size a Solar Air Heating System: Practical Tips.


Calculating Heat Requirements For A Solar Air Heater

Solar air heating systems are a fantastic way to utilise renewable energy sources to lower your heating costs and reduce your carbon footprint. Before you begin your project, it’s essential to understand how to size a solar air heating system correctly.

In this post, we’ll walk you through some practical tips on calculating heat requirements for a solar air heater, including understanding heat loss, identifying heat requirements, heat transfer coefficient, and factors that affect heat requirements.

Understanding Heat Loss

When sizing a solar air heater, it’s essential to understand heat loss. Heat loss in buildings occurs through walls, windows, doors, and roofs. In colder climates, heat loss can be significant, making it challenging to maintain a comfortable temperature. Naturally, the amount of heat lost will vary from building to building, and this greatly impacts the size of the solar air heating system needed.

Identifying Heat Requirements

When calculating heat requirements for a solar air heating system, it’s necessary to consider the size of the area you’re trying to heat, and the appropriate temperature range. Most buildings require a winter temperature range of approximately 20-22°c (68-72°f). Still, this can vary depending on building type, geographic location, and the occupants’ needs.

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Heat requirements will vary based on the region in which you live, the type of building, and the energy efficiency of the building.

Heat Transfer Coefficient

The heat transfer coefficient relates to the rate at which heat transfers through a surface and is an essential consideration when sizing a solar air heating system. Typically, walls, roofs, windows, and doors will have different heat transfer coefficients, which impact the amount of heat loss within a building.

By optimising the heat transfer coefficient, you can make your building more energy-efficient.

Factors That Affect Heat Requirements

Various factors affect heat requirements, including window area, building orientation, the thickness of walls, and the amount of insulation. Buildings with large window areas will lose more heat, while poor building orientation can impact how much sunlight is received throughout the day.

The thickness of walls affects how much heat will be lost or retained, and without proper insulation, a building cannot maintain heat. Additionally, the number of occupants within a building can affect how much energy is used.

By considering these factors, you can accurately calculate the heat requirements for your solar air heating system, ensuring it is appropriately sized for your building and energy needs. By following these practical tips, you can achieve a more energy-efficient and sustainable home or business that relies on renewable energy sources.

Sizing A Solar Air Heating System

If you’re considering installing a solar air heating system, it’s important to size it correctly. Proper sizing ensures that the system operates efficiently and provides sufficient heat. Here are the factors you should consider when sizing a solar air heating system.

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Type And Size Of Collector

The size and type of the collector are critical factors in determining the size of your solar air heating system. The collector should be large enough to harness the required sunlight and generate enough energy to heat your home. It’s also important to choose a suitable type of collector based on your heating needs.

The common types of collectors include flat plate collectors and evacuated tube collectors.

Area Of Collector

Another aspect to consider is the area of the collector. The size of the collector should match the size of your home’s heating requirement. The larger the collector area, the more heat it can generate. In general, a rule of thumb is to have a collector area of approximately 50 to 100 square feet per person.

Thermal Efficiency

Thermal efficiency is a measure of how effectively the collector can capture the sun’s energy and convert it into heat. Look for collectors with high thermal efficiency levels to ensure that your solar air heating system generates maximum energy. The higher the efficiency, the smaller the collector you need to generate the required heat.

Air Flow Rate

The air flow rate is another factor to consider when sizing a solar air heating system. The air flow rate is the amount of air that the system moves per minute and depends on the fan’s size and speed. When sizing a system, consider the volume of the space to be heated, the desired temperature, and the rate of air exchange.

An efficient solar air heating system should move as much air as possible per minute without requiring unnecessary power.

Storage Capacity

The storage capacity of the heated air is also an essential factor to calculate when sizing a solar air heating system. The storage capacity depends on factors such as the size of your home and how many occupants it has.

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You also need to consider factors such as insulation and climate zone to determine the appropriate storage capacity. The larger the storage capacity, the longer the system can provide heat without sunlight.

Selecting Appropriate Materials

When installing a solar air heating system, consider using high-quality, durable materials. Choosing the right materials can ensure that the system operates efficiently, lasts for years, and does not require frequent maintenance. Key materials that affect the performance and durability of the solar air heating system include the collectors, ductwork, and fans.

By considering these five factors, you’ll be able to size your solar air heating system correctly. Proper sizing will ensure that the system operates effectively, providing you with consistent and reliable heating at an affordable cost.


As we’ve explored in this guide, sizing a solar air heating system can be a complex process that requires careful consideration of several factors. To ensure that your solar heating system functions optimally and provides you with the desired level of energy savings, you must take into account the size of your property, your heating needs, and your budget.

It’s also key to bear in mind that the energy needs of every household differ, and therefore the size of the heating system should be tailored to your specific requirements. By following the steps outlined in this guide, you should now be well equipped to begin the process of sizing a solar air heating system for your home or business.

Consulting with a reputable solar energy installer can also help you arrive at the best solution for your energy needs. With the right sizing and installation of a solar air heating system, you can significantly reduce your utility bills, enjoy more comfortable indoor temperatures, and help contribute to a greener world.


I am a mechanical engineer and love doing research on different home and outdoor heating options. When I am not working, I love spending time with my family and friends. I also enjoy blogging about my findings and helping others to find the best heating options for their needs.