Here we are again. It’s early winter and we can feel the cold creeping upon us.

By this time people without air-conditioners in their homes or offices are scrambling to buy electric heaters and blankets at retail outlets instead of calling their local air-conditioning contractor for a quote on a Gree air-conditioner.  So what’s wrong with that? Let’s debate this for a moment and do some comparisons between space heating using electric heaters vs air-conditioners (heat pumps)

Safety concerns  

Electric bar heaters are extremely dangerous because of the sheer heat emanating from their elements. These are often positioned near to curtains or furniture, creating a high probability of fire.  Often, when these bar heaters are bumped over, there is a high probability of setting carpets or wooden flooring alight. A further problem with electric heaters is that many of them are fitted with inferior electric cables and plugs. Often, they are plugged into extension leads which are either too long, coiled and thinner than the prescribed thickness of 2.5mm2. These simple errors will eventually lead to overheating cables, plugs and subsequent fire damage, even loss of life.

The opposite of this happens when good quality air-conditioners such as Gree are fitted by reputable contractors. Gree air-conditioners consume less than a third of the input power electric heaters do. We will go into more depth regarding this later but because of this, much less stress is put onto one’s power outlets and wiring. Gree Air-conditioners also go through stringent CB safety regulations and are fitted with the correct cables, plugs and safeties in order to prevent overheating and subsequent fire. Secondly, contractors will terminate air conditioners properly into electrical distribution boards using the correct sized cables, circuit breakers and isolators.


When looking at efficiency, the following differences between electric heaters and air-conditioners apply: Elements found in electric heaters are very inefficient – for every 1 Watt of power consumed, the output would be 1 Watt or less. This translates to an energy efficiency rating (E.E.R/C.O.P) of 1.0  In other words, a heater with an output of 3000W will also consume 3000W so for every R1.00 you spend, you will get only R1.00 of heating.

With air-conditioners, the picture is totally different: The heating output of a 12000BTU Gree Lomo Inverter is 3800W (800W more than the heater) but the power input is only 1000W. This translates to an energy efficiency rating of 3.6 (vs 1.0 of a heater) which means that the air-conditioner is  3.6 times more efficient than the heater and for every R1.00 spent on power, you will receive 3.6kW of heating. Now we will move on to the reason why it’s even faster than the 3.6 times mentioned – it has to do with airflow.


Most heaters don’t come with fans and those that don’t have sufficient airflow to spread the heated air through rooms quickly enough. Users are forced to wait for hot air to rise to the ceiling by itself, then spread across the ceiling. From there the hot air cloud takes time to fill the room in a downward direction towards the floor, however it takes so long that the air up to knee level almost never reaches the required temperature because hot air will always rise if not forced down. This is called “lamination” which basically means that there can be huge differences between the air temperatures at floor level compared to ceiling level – sometimes as much as 8 degrees Celsius.

Air conditioners work differently in that they create what we call “air changes” which is a much more efficient way of spreading heat. A Gree 12000BTU Lomo inverter has airflow of 600m3/hour, which will create 11 air changes every hour in a 54m3 room. This means the entire volume of air in the room goes through the aircon and is heated 11 times every hour. Apart from this, hot air is forced down to floor level and the “lamination” effect is small. What this also means is that an air-conditioner will be able to cycle off after reaching the set temperature while an electric heater will have to run for hours afterward.

This brings us to our theory that an air conditioner can be 6 times faster and more efficient than an electric heater. We have already established that the AC is 3.6 times more efficient but if we add the differences that airflow, air changes and lamination bring about, it is clear that one cannot compare the performance of an electric heater to a quality air-conditioner such as Gree. In fact, it might easily be more than 6 times faster and more efficient.


The calculation below measures the difference in cost between heating up a room with an air conditioner vs an electric heater, based on the (conservative) assumption that the aircon will heat up the room to the required temperature 2 times faster than the heater :

Heater: 2x hours x 3000W = 6000W x R2.00/W Electricity cost/unit = R12.00

Aircon: 1 x hour x 1000W = 1000W x R2.00/W Electricity cost/unit = R2.00

Difference : R2.00/R12.00 = 6 (6 times more efficient)


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