This guide assists not only in selecting the appropriate air conditioning unit for your needs, but also get the most out of it, once it’s up and running.

Air conditioning 101

When we mention ‘aircon’, images of cool rooms on those typically hot, humid summer days come to mind. However, air conditioning units are equally capable of warming up a room during chilly winter evenings. Whether it’s for keeping you cool or taking the edge off winter, choosing the right aircon and knowing how to use it, will help you to get the most out of it.

Air conditioning 101

Choosing the right-sized air conditioning unit for your home

The key to an air conditioner’s efficiency, whether heating or cooling, lies in choosing the right-sized unit for the space. Air conditioners come in various sizes, rated in British Thermal Units (BTUs). This indicates how much heat the unit can add or remove from the air per hour in a specified area. Choosing the right BTU for your space is crucial for optimal efficiency. Here’s how you can calculate the right size:

Air conditioning 101
  1. Start by measuring the room’s floor area. Calculate the square meterage (length times breadth in metres). Remember, we are working in square metres, not cubic metres.
  2. Calculate required BTU: In South Africa, an air conditioner should generally have a capacity of about 500 BTU per square metre to efficiently cool or heat a space. That means a 20 m2 room would require 10 000 BTUs, and a 50 m2 room would need 25 000 BTUs. This calculation assumes a standard ceiling height of between two and a half and three metres.
Air conditioning 101
The above calculation gives you the theoretical minimum size of the air conditioner needed for a room without additional heat sources, such as large windows facing direct sunlight, high-traffic areas or rooms with lots of electrical equipment. Other factors, such as ceiling insulation or double volume ceilings, can also affect the performance of your aircon. In a home, it might be wise to opt for a size larger than the minimum size the calculation suggests.

Installing an aircon with a lower BTU than needed would result in the unit overworking, potentially leading to overheating and unnecessary wear and tear. Conversely, a unit that’s too large can cool the room quickly but may not effectively remove moisture, leaving the environment cool but damp.

Now that you know the basics of choosing the right sized aircon, it’s time to grab that tape measure and measure out your room. Soon your home will be the perfect temperature, come summer or winter!

Air conditioning 101

Get the most out of your aircon

Now that you know that you have the right size unit for your room, you need to understand how to maximise the efficiency of your air conditioner.

An aircon’s compressor, similar to that of a fridge,, compresses refrigerant gas, which cools under pressure. The compressor is the most power-hungry part of an air conditioner. A common misconception is that the set temperature is what the aircon immediately produces. Instead, this is the target temperature at which the thermostat will switch the compressor off. An aircon can realistically produce air about 10°C cooler than the ambient temperature, so on a hot 30°C day the aircon might cool air to about 20°C, gradually lowering the room’s temperature.

Setting a realistic temperature around 22 – 23°C is crucial, especially on extremely hot days, to avoid non-stop compressor activity and high energy consumption.

Air conditioning 101
Over time the technology of aircons has improved vastly, which has led to Inverter aircons being widely available. A non-inverter or fixed-speed aircon runs at a constant speed, cooling or heating the air. a As in the case of a fridge, it only switches off when the desired temperature is reached. When the room warms up or cools off again, the aircon switches on again at full speed and full power. It’s the constant switching that draws high current and adds significantly to your electricity bill. Inverter aircons adjust the compressor’s speed based on the room’s temperature, which helps maintain a consistent temperature and reduces power usage. Although more expensive initially, inverter units are quieter, provide more even cooling or heating and are more cost-effective in the long run.
Air conditioning 101
When it comes to installation, air conditioners smaller than 18 000 BTU can be plugged into a standard outlet, while larger units require dedicated circuits and professional installation. Builders offers aircon installation services, making it easy to leave the installation to the experts.

Remember, everything you need to keep your home warm in winter and cool in summer is available from Builders, wither in-store or online at

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