How to save electricity - Midrand Estates

CIRCULAR ON LOAD SHEDDING N O 5
22 February 2008
SAVE ELECTRICITY WITHOUT COMPROMISING ON YOUR LEVEL OF
COMFORT
The recent load shedding introduced by Eskom has lead to a mixture of suggestions on how to save electricity – some
technically sound, some with less accurate deductions based on misplaced assumptions.
The emotions of the general consumer were also mixed, ranging from an understanding that we need to save on
natural resources to total indignation of the inconvenience experienced.
We were advised by Eskom that should a general load reduction of 10% be attained, the threat of load shedding will
reduce significantly. The question remains – where do you start in the process of saving; what impact will it have on
your comfort levels; what will the capital cost be
We have also been advised by Eskom that a differentiated tariff and consumption ration system will be introduced
shortly. Final details are expected soon with an anticipated implementation date of 1 April 2008. Indications are that
residences will be allocated an initial quota (in the order of 800 kW.h) at the normal rate. Thereafter, the rate will
increase in steps up to R2/kW.h.
All consumers are thus advised to consider methods of saving electricity and to implement such measures without delay.
ANALYSIS OF TYPICAL RESIDENCES IN MIDRAND ESTATES:
Attached hereto a summary of electricity consumed in 3 types of housing in Midrand Estates. The results may be
summarized as follows:
MONTHLY 2007 CONSUMPTION (KW.h)
Winter Summer
Large house 3 700 units 2 700 units
Medium House/Large Townhouse 2 500 units 1 800 units
Medium Townhouse 1 100 units 800 units
MEASURES TO REDUCE ELECTRICAL CONSUMPTION
1. Change lamps to CFL’s (compact fluorescents)
Whilst lighting only amounts to 10% of the average consumption in a house, it is a quick and easy (and cheap)
way to save. By replacing 50% of the existing lamps with CFL’s – and switching off lights not required –
electricity consumed for lighting can be halved. CFL-lamps cost in general between R50 and R100 per lamp,
but lasts considerably longer.
Additional info and myths:
1. A 12 volt lamp of 50W uses less electricity than a 220 volt lamp of 50W Wrong!
Irrespective of the voltage, 50W remains 50W – in fact the 12 Volt system has losses through the
transformer and uses more electricity!
2. A CFL-lamp cannot be dimmed Correct!
For that reason we recommend you replace CFL lamps only in areas where you never dim the lights.
2. Adjust the hours on your swimming pool pump
Your pool pump consumes approximately 10% of your residence’s electricity. Speak to your swimming pool
advisor and adjust the hours – remember that the hours can be reduced even further during winter.
Additional info and myths:
1. If the pump runs late at night it does not matter Wrong!
Whilst it will assist in reducing the peak load, we need to reduce overall electrical consumption –
every reduction in consumption will help.

2
3. Switch off the under floor heaters when not required
Space heaters and under floor heaters consumes between 25% and 40% of the electricity in a household
during the winter months. Whilst most people will switch their space heaters off when leaving a room for a
prolonged period, under floor heaters are not switched off as it is difficult to reach them. MES has assisted in
the development of Programmable under floor heater thermostat (PUHT) and will subsidise the sale of the
units. Cost of the unit (including installation) will be approximately R650 each. The electricity ‘saved’ in winter
months per unit will be in the order of 100 kW.h units – approximately R50/month @ 50c per kW.h or
R200/month @ R2/kW.h.
4. Geysers with water pre-heated by solar radiation
SUMMARY:
The heating of water consumes between 20% and 25% of a house’s electrical consumption the whole year! It
is recommended that solar vacuum tubes be installed and be coupled to the existing geyser. Such an
installation will use the sunlight to pre-heat the inflow of water to the geyser with a circulating pump being used
to draw colder water from the geyser and pass it through the solar heat exchange unit. The benefit of using
the existing geyser lies in the availability of the heating element to heat the drawn down geyser during night
time in preparation for an early morning shower.
The solar system compatible with a 200 litre geyser will cost between R8 000 and R12 000 installed and
should ‘save’ 100 kW.h units per month for 12 months of the year.
Additional info and myths:
1. I can save R500 worth of electricity per month by installing a timer switch on my
geyser (or switching the geyser off during the day)
Wrong!
The cost involved in raising the temperature of 200 litre water from 10 ºC to 60 ºC is approximately
R3. This will equate to R90 per month for a 200 litre geyser – it is thus impossible to save R500.
You can, however, save 10 – 20 units (R10) per month by switching off your geyser during daytime –
this will not apply if you have a solar heated geyser.
2. How can I save further Information
Limit heat loss from your geyser. Once heated, your geyser will ‘loose’ heat due to the temperature
gradient. There are three ways in which the heat loss can be limited:
i) Lower the setting on your geyser to 60 ºC;
ii) Install a geyser blanket to improve insulation of your geyser – cost of the blanket is R150 -
expect to save 10 to 20 kW.h units per month;
iii) Do not install the geyser outdoors on a concrete slab exposed to the elements – the ambient
temperature may be up to 15 degrees lower during winter than a geyser installed in a roof
void, leading to an increased heat loss.
South African residents are challenged to save electricity where possible to alleviate the demand of electricity and
reduce our carbon footprint.
A five point plan is proposed to save electricity in any residence, namely:
1. Change 50% of the internal lamps to CFL’s;
2. Change 100% of the external lamps to CFL’s;
3. Reduce the number of hours the pool pump motor runs;
4. Install solar vacuum tubes to heat the geyser for the evening cycle – retain the normal element for the
early morning cycle;
5. Reduce the number of hours the under floor heater remains switched on during winter.
The adjusted consumption figures may be as follows:
MONTHLY CONSUMPTION (KW.h)
(BEFORE AND AFTER SAVINGS)
Winter
Summer
Before After Before After
Large house 3730 units 2510 units 2710 units 2180 units (a saving of 25%)
Medium House/Large Townhouse 2450 units 1720 units 1770 units 1440 units (a saving of 25%)
Medium Townhouse 1090 units 910 units 750 units 620 units (a saving of 17%)