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Eskom has called upon all consumers to use electrical equipment more efficiently. One of the items specifically
mentioned is air-conditioners.

Throughout the country Eskom has called upon its own sites to set their air-conditioning systems to about 22 – 23
degrees centigrade in an effort to save energy.

In the summer heat, air conditioners are many people’s appliance of choice to keep cool. More often than not, “cool”
tends to be freezing cold with thermostats set at 18 degrees or even lower.

Heating, ventilation and air-conditioning, HVAC for short, contribute an estimated 5 400 MW to electricity demand in
peak periods. This is approximately 15% of South Africa’s current peak demand consumption.

On an annual basis, HVAC accounts for some 4 000 gigawatt hours of electricity consumption in South Africa.

By implementing a few simple measures, the conservative estimate is that HVAC load can be decreased by at least

According to air-conditioning researchers specialising in energy efficiency a little bit of logic can go a long way to
decrease the energy consumed by air conditioners without inconveniencing homeowners, employees or customers.

Air-conditioning at the office
In commercial settings, such as office buildings, an effective way to reduce the workload and energy consumption of
an air-conditioning system, is to use ambient air to cool the building down at the start of the day. The outside air,
even in summer, is fresh and cool early in the morning and by switching the air-conditioning system’s fans on, the
cool natural air is drawn into the building. Not only does it lower the inside temperature, but it also flushes out the
stale air from the previous day.

In this way, the building is cool and fresh when the employees and customers arrive, and the intensive chillers need
only start operating towards mid-morning.

A slight adjustment to the temperature setting of the air-conditioning system can result in substantial savings. It is
advisable that the difference between the inside and outside temperatures should not exceed 10 degrees Celsius.
Compared to current practices, this means that air conditioners can be set a degree or two higher in summer and a
degree or two lower in winter. Not only would the air-conditioning not have to work quite so hard to maintain the
desired temperature, but health wise it is also wiser to not subject the body to severe temperature contrasts.

For example, if the outside temperature is 35 degrees and the inside temperature is maintained at 25 degrees
instead of 20 degrees, a 33% saving in energy consumption will be realised.

Towards the end of the working day, the building’s air-conditioning system could “wander” i.e. allowing the
temperature to gradually increase, given that employees are due to leave soon and will then encounter the
temperature outside. It is not energy efficient to maintain a cool interior long after the people who needed it, have
Air-conditioning at home
Residential air-conditioning users can apply the same principles stated above to reduce their energy consumption.
Cool down the “bricks and mortar” of the house early in the morning by making use of the cool outside air. Open
doors and windows and use the air conditioner’s fan to circulate the fresh morning air through the house.

As a result, the house will take longer to heat up as outside temperatures rise, thereby putting off the need for the air
conditioner’s chillers to take effect.
How to avoid using an air conditioner
It is surprising to realize how many measures can be taken to control the indoor temperature without having to resort
to air-conditioning.

Buildings themselves can be used to “store” coolness. By shading a building from the outside by means of trees,
horizontal metal blinds, awnings or heat reflecting film on windows, direct sunlight is prevented from heating the
interior. The outside temperature will rise much quicker than the inside temperature, once again delaying the need
for air-conditioning.

Ceiling insulation is one of the most effective ways of beating the heat. Proper insulation slows the process down of
heat entering a building through the roof, while in winter preventing hot air from escaping through the roof.

Appliances and equipment, such as urns, computers, copiers and lights give off heat while in operation. Therefore,
switching them off when they are not in use would further cool down the temperature inside a room or building.

Produced by: Generation Communication
             DSM 0002 Revision 2 (October 2010)
             Source: Eskom Demand Side Management

See also:       DSM 0001 Practical hints on saving electricity
                DSM 0003 Facts and fiction about your geyser

For more information on Eskom related topics see the Eskom website (
Select the “Knowledge Centre” and “Facts and Figures”

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