It is estimated that lighting contributes 6% towards the total energy consumption of households in South-Africa. Should all incandescent light bulbs be replaced with a LED version this consumption can be reduced to about a quarter of the original consumption. The table below is an indication of how this saving will look at home. Keep in mind that the tariffs are for Potchefstroom. The graph summarizes the life cycle cost of the different lights visually.
Lighting Consumer Profile and Financial Model
Units Incandescent globe Halogen globe CFL LED
Cost (R) 9.90 17.15 24.90 109.50
Light output (lm) 810 850 850 810
Input power (W) 60 53 15 12
Equivalent input power (W) 60 60 60 60
Current (A) 0.26 0.2 0.11 0.0047
Power factor 1 1 0.55 0.8
Life time (h) 1000 2000 8000 15000
Output at end of lifetime 0.8 0.8 0.65 0.9
Light colour (K) 2700 3100 2700 2700
Light colour Warm white Warm white Warm white Warm white
Starting time (s) 0.00 0.00 1.50 0.50
Warm-up time to 60% output(s) 0.00 0.00 20.00 2.00
Mercury content (mg) 0.00 0.00 1.70 0.00
Energy classification E D A A+
Dimmable Yes Yes Yes* Yes*
Energy cost measurement (kWh) 1.51 1.51 1.51 1.51
Efficacy (lm/W) 13.50 16.04 56.67 67.50
Number of globes needed (N) 15.00 7.50 1.88 1.00
Cost of globes (R) 148.50 128.63 46.69 109.50
Cost of energy (R) 1354.50 1196.48 338.63 270.90
Total life cost (R) 1503.00 1325.10 385.31 380.40
The first step in the life cycle cost calculation was to calculate how many incandescent, halogen and CFL globes are needed to provide light for the same amount of time as a single LED. With this information the cost of globes needed, can be calculated. As can be seen from the table the incandescent and halogen light bulb costs have already surpassed the LED globe cost of R109.50.
The second step is to calculate the cost of the total electrical energy used throughout the life cycle of the globes, as can be seen from the table, the LED and CFL globes uses the least electrical energy whereas the incandescent and halogen light bulbs uses the most electrical energy. The reason for this phenomena is that the incandescent and halogen light bulbs converts more energy to heat than light and the CFL and LED globes converts more energy to light than heat.
After completing both steps one and two, the total life cycle cost can be calculated by summing the cost of globes needed and the cost of electrical energy.
When it comes to lights, five very important characteristics that are often overlooked is the power factor, mercury content, cap fittings (bases), shapes and sizes and the light colour.
As can be seen from the table, the power factor of the CFL is the lowest and it has a certain amount of mercury in it. Although a low power factor does not influence residential electrical energy bills, it does influence the load that our local electrical energy suppliers have to deliver, thus by keeping our residential power factors as high as possible, we can decrease the load and minimise load shedding. More about power factor can be seen at: http://en.wikipedia.org/wiki/Power_factor
Also, mercury is a very harmful to our environment, thus the CFL is not very environmentally friendly when it comes to the materials that were used to manufacture the globe. All four of the different types of light technologies come in a variety of shapes and sizes and there are also a large number of different types of bases.
When buying some of the new light technologies, keep in mind that the colour output of the light globes may vary from the colour output of the incandescent and halogen light bulbs that we have become accustomed to. The figure below shows the colour output of incandescent, halogen, warm and cool white CFLs and LEDs.
The incandescent and halogen light bulbs have light outputs between 2700 kelvin and 3100 kelvin, whereas the new CFL and LED globes vary from warm white (2900 kelvin) to cool white (4100 kelvin).
In conclusion, the LED has the lowest lifecycle cost making it the most economical, it uses the least electrical energy and it does not have any mercury in it making it the most environmentally friendly. Thus, when replacing old light bulbs, spend a little more money on a LED and save more than R1100 over the lifecycle of a single LED. By replacing all incandescent light bulbs with a LED, the electrical energy usage of lighting in homes can be reduced to 1.2%, saving 4.8% on lighting alone. This is the maximum possible savings.