Energy Efficiency Basics

Saving energy in the home will result in financial savings but needs to be prioritized in order of importance. The financial equation of energy saved against the investment in the energy saving technology needs to be compared.

Saving money is the primary motive behind energy efficiency. Improving ones carbon footprint is also a significant benefit.

All energy efficiency requires investment. The payback on the investment needs to be carefully worked out, taking into account not only the electrical savings and the financial benefits of the savings, but also the capital cost and the loss of income from the funds invested into the energy efficient technology. Generally the payback on energy efficiency will significantly outperform the returns from the money if invested. 

The options are as follows:

  1. Water Heating
  2. Lighting
  3. Appliances
  4. Insulation
  5. Heating /Air Conditioning
  6. Solar Photovoltaic

In order of priority, the following steps should be considered based on the payback period of each:

Type of TechnologyTypical Payback Period (system dependent)Anticipated Lifespan
Solar Water Heater 2 - 6 years 20 - 25 Years
Insulation (if applicable) 2 – 8 Years 25 Years
Lighting (CFLs & LEDs) 3 – 6 Years 60 Years
Solar Photovoltaics 6 – 11 Years 25 Years +
Heat Pumps (domestic) 4 – 12 Years 15 Years
Image Credit: Steven Depolo

The most power hungry device in the home is an electric geyser using an electrical resistance element. The most efficient energy saving technology for replacing electrical heating in a domestic home is a solar water heater (see our section on the basics of solar water heating).

Heat pumps are an alternative to solar and electrical resistance elements, but have generally been found not to deliver the promised electrical savings in the home, due to a combination of reasons. Consequently all energy incentives for domestic heat pumps were suspended. However heat pumps in a commercial environment where large volumes of water are being heated, for example hotels, can be extremely attractive saving up to 70% approx. of the energy consumed through electrical resistance elements. 

Low-flow shower heads where the amount of hot water used reduces to approximately 10 litres per minute, instead of 15-30 litres per minute, indirectly saves energy by reducing the amount of hot water consumed, and therefore enables the hot water to go further. They do not save the electricity directly.

Staying with electric water heating through a resistance element is of course an expensive option if a consumer believes they cannot afford to go solar. Consumers should consider some of the solar rental models, which enable the consumer to be better off immediately over staying with an electric geyser, without the large capital expenditure of buying a solar system.

If the electric resistance geyser is to remain consumers should for energy efficiency set the thermostat to a maximum of 55 ºC, check that the element is not corroded or heavily coated with lime scale, (this can use up to 30% more power for heating the water), make sure the sacrificial anode is not exhausted, and consider a geyser blanket. To save energy smaller baths or shorter showers will save electricity. 

If a home has a mains gas connection, gas boilers are an attractive option to consider being considerably cheaper to run than electric geysers.

Other technologies that claim to save electricity, for example induction geysers need to be approached with considerable scepticism. Frequently electrical savings claims are found to be spurious and misleading. Before buying, empirical evidence of savings should be provided.

LED light bulbs

The 2nd area to address for energy efficiency after solar water heating is lighting. With the prices of high quality LED’s having fallen by 50% in real terms (after exchange rates) in the last 2 years, reducing your electricity bills through replacing inefficient old lighting technology is now a real option, with attractive financial returns on the investment.

As an overview:

  • Incandescent bulbs are very inefficient with the majority of the electricity being wasted through heat.
  • Halogen bulbs do not save any energy over incandescent.
  • Low voltage lighting (12V) is actually less efficient than mains 220V lighting.
  • CFL lighting can save up to 70% of the electricity used in an incandescent bulb and enjoy a much longer life.
  • LED lighting can save up to 85% of the energy in an incandescent bulb for the same lumens output. They also enjoy a very long life of up to 60 years before failing.

Before investing in LED lighting technology consumers need to be aware of some of the potential pitfalls.

  • If LED down lights are not correctly fitted with sufficient space for the heat to be dissipated efficiently, their anticipated life may be reduced to months or a few years.
  • The lumens output is not always as much as claimed particularly with cheaper product from unknown brands. A 5W LED may for example only produce 4,5W output after a short period, rendering the light output to be inadequate. For example a 6W LED in replacement of a 50W halogen will probably be a better bet than a 5W that claims to have the same lumens output as the 50W halogen. 
  • A number of manufacturers now offer a variety of light colors, for example yellow light rather than the harsh cold daylight colors which many people find unattractive. Dimmable LEDS are also now available.
  • As the investment can be considerable, it is advisable to buy better known brands with strong warranties and as with all energy efficiency to do the research. There is a lot of information readily available over the Internet.
  • The return on capital expended can provide a payback on the investment of 2 years or less, but only if the LED is good quality, and it is correctly installed.
  • DIY installation on down lights is generally simple and straightforward, and should only take about 2 minutes per fitting.

Modern day appliances such as washing machines, dishwashers, fridges and freezers are all considerably more efficient than only a few years ago. Swimming pool pumps have also improved performance and energy efficiency. An ‘energy rating’ label should be shown on the product.

As a general rule, the more expensive and the higher the quality of the product, the greater the energy efficiency will be. In respect of cooking, gas hobs are more efficient than electric, providing more heat output and arguably more control than electric or induction hobs. Most consumers prefer electric ovens to gas, and these are energy hungry. As a rule of thumb, the better quality ovens are usually more efficient than cheaper models.

As with all energy saving, the comparison between the financial saving needs to be compared with the cost of the appliance. 

Insulation

Heat loss and air conditioning losses can be highly significant. Roof insulation in homes makes a considerable difference in winter avoiding heat loss and can contribute to keeping homes cooler in summer. Relatively cheap to install with a reasonable payback time on expenditure, it is one area of energy efficiency that should be a priority in saving energy and money. A number of different materials are available, including fibreglass matting, spun mica and wool sales agents should be able to advise you. 

Double-glazing of windows makes a significant difference to both noise pollution and heat loss. Extremely popular in colder climates, in South Africa the payback time on expenditure will be longer, and extensive research needs to be undertaken to find the right solution for your home.

Electric heater

Heating of homes in South Africa is very dependent on location. As most homes in South Africa are not equipped with central heating, the options are localized heating through gas bottles, fireplaces fuelled by both coal and wood, oil filled radiators and other types of electric heaters. In all cases the options are both expensive and not very efficient.

Oil filled radiators are typically 1 500 Watts, approximately half the electrical consumption of an electrical geyser. Multiple radiators are expensive to run. 

Under floor heating with electricity or water pipes is arguably a luxury, providing a pleasant overall ambient experience. Costs of under floor heating using either electricity or water are similar. Running costs again are similar, unless a heat pump or solar water heating is used. In general the investment is substantial.

Where air conditioning units are used for either cooling or heating, the tips for saving money and increasing efficiency are to lower the thermostat setting, and to make sure the filters and equipment is regularly serviced and in good condition. The latest air condition units, as with many appliances, are considerably more efficient than those manufactured a few years ago.

Approximately 95% of Eskom’s generation capacity is from coal which contributes significantly to making South Africa one of the top 10 emitters in the world. The fundamental problem from a carbon perspective is that coal is not only a cheap form of energy, but South Africa does not have many alternative traditional fuel sources. 

Gas with a carbon footprint approximately 50% of coal, is limited with some supply offshore from Mossel Bay, and expectations from shale gas in the Karoo basin, which although called a ‘game changer’ is unlikely to be developed in the next 10 years. It is also contentious from an environmental perspective and is water-intensive. 

Nuclear output (with a low carbon footprint) is less than 6% of generation capacity, and future nuclear development is not only expensive but is challenged on safety and environmental grounds.

Large hydro with a low operational carbon footprint is expensive to build, and there is limited opportunity in South Africa. Cahora Bassa on the Zambesi in Mozambique accounts for approximately 6% of Eskom’s power. Future plans for developing hydro from the Congo have been endorsed by the government, but in reality have been on the drawing board from the mid 1960’s.

Consequently personal energy efficiency in South Africa is extremely important from a carbon perspective. Approximately 1 kg of carbon is saved for every kWh saved.

In this respect solar water heaters offer the greatest opportunity for reducing an individual’s carbon footprint.