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Updated : 16/10/2016


How to save electricity on lighting

Light Bulb Cost Calculator   (energy + initial & replacement bulbs)
Electric Cost (R/kWh):  
5-Year Cost
of bulbs
Hours on
per day
Standard CFL LED

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Lighting is is the third-biggest energy user in most homes.  But it's probably the easiest area to save in. You can start saving up to 70-90% right away by simply using new LED or CFL lights.

Environmental Defense has the best explanation of what's wrong with regular light bulbs:

"Though we call them light bulbs, traditional incandescent bulbs are actually small heaters that give off a little bit of light? Something you will know from experience if you've ever touched a bulb that's been on for a while. These bulbs were technological wonders when they were patented in 1880, but today they are inefficient dinosaurs. They waste energy and money, and they are responsible for millions of tons of global warming pollution."

There are other easy ways to save money on lighting besides switching bulbs, such as putting lights on timers or motion sensors, and just being more diligent about turning off lights when they are not needed.

A single 100-watt bulb left on continuously will cost R89.28 a month (assuming R 1.24/kWh).

Use CFL or LED lights.

There are two, energy-efficient, alternatives to incandescent globes:  LED or CFL.  Both are good choices, producing very good light, and are direct replacements for your current globes, enabling you to start saving energy immediately.
LEDs are more energy efficient but the current cost of globes is still very high, to replace a 100W incandescent globe cost R215 for an LED bulb vs. R40 for a CFL. You'll make up the extra cost for the LED from the energy it saves, but this could take several years depending on the relative cost of the globes and how much you pay for energy. Until the cost of LED globes comes down to a reasonable level or the cost of energy goes through the roof just go ith CFL.  If you want to see the relative operating costs of Incandescents, CFLs and LEDs take a look at the calculator on the right to see how much you can save.

Please note that the costs the costs are for a period of 5 years. This is because the life expectancy of current LEDs is supposedly about 3 years.

The difference between the different kind of light bulbs:

Incandescent vs. CFL vs. LED
Incandescent CFL LED
Cost over 25,000 hours(Total) R3752 R970 R711
Cost of 100-watt equivalent bulb R13 R39 R215
Cost over 25,000 hours(bulbs) R52 R195 R215
Cost over 25,000 hours(electricity) R3100 R775 R496
Life (in hours) 1 500 5 000 25 000
Life reduced by cycling on/off Very Little A little bit Not at all
Light output over its life Constant ~70% of initial brightness by end of life (30% drop)
Dimmable All models Some models
Can be used in enclosed fixtures All models Some models Never
Good in freezing temperatures All models Rare models All models
Light quality Excellent Excellent Excellent
Time needed to get fully bright Instant ~1 minute Instant
Heat generated A lot A little A little
Toxic mercury No Barely No
How breakable Fragile Fragile Strong
Watts for 1600 lumens 100 25 16
Note: All prices in ZAR as of 2013
Lumens-to-Watts Converter
LED Watts
Comparing apples-to-apples is difficult because different bulbs disperse the light differently.  However, this table is accurate enough for practical purposes.

Choosing a replacement light

When choosing to replace a an existing incandescent light with an energy-efficient alternative it is only natural to want a replacement that produces the same quality of illumination but with lower energy usage. The two principal factors that define the quality of illumination are the brightness and colour.

There is a large difference in cost between the various types of lights and this become a significant in the overall cost of operating a light. Whereas those with a passion for the environment may accept paying more to use a light with a lower environment impact there are those who are primarily looking the effect a cost reduction in their energy bills. For the latter group, therefore, the life expectancy of the higher cost alternative lights becomes a significant issue.


CFL lights are generally sold as either cool white or warm white. Warm white, has a more pleasing yellowish tint suitable for living areas whereas cold white is a harsher bluish light more suitable to bathrooms and kitchens. The color temperature (often printed on the package) tells you exactly how warm or cold the light is. Warm is 2700-3000k, and cold is 3600-5500k.


We all know, by experience, how bright a 100W incandescent light is but how bright is an 11W CFL or a 4W LED? Many manufacturers and retailers indicate on the packaging how bright their CFL or LED lights are in watt-equivalents. However my personal experience is that more often or not they exagerate the brightness of their product.
Brightness is measured in lumens and therefore a replacement light should provide the same number of lumens. The table above right shows power level (Watts) of each type of light required to produce a specific lumen level. For example a brightness of 1600 lumen is produced by 100W incandescent light, a 27W CFL or a 16W LED.


When buying CFLs, make sure they either have the Energy Star logo or come with a warranty. The cheaper CFLs can burn out really fast.

Use lights effectively

Turn off lights

Turn of lights when you're not using them, even for just a few minutes.
The idea that lights use extra electricity to start up is a myth. You will save electricity every time you turn the lights off, no matter how short the off duration,and whether they're regular lights or fluorescents.
You might have heard that you shorten the life expectancy of a light by cycling it off and on, but the effect is so small as to be negligible and you can safely turn your lights off every time you leave the room, no matter how short the duration.

Use a motion sensor for outside lighting

Exterior security lights automatically shut off after 1-15 minutes, so you're not paying to run them all night. However do note that you cannot use CFL's in security lights because the fixtures cycle a very small amount of voltage through the lights constantly which reduces the life expectancy of the CFL light.

Use a motion sensor for interior lighting.

If you can't remember (or can't be bothered) to turn off the lights throughout your house, a motion-sensor switch will shut them off for you automatically.

Use the lowest practicable wattage bulbs for lights that are always on.

Replacing 100-watt bulbs with 60-watt bulbs reduces energy usage by 40%. Replacing them with LED or CFL lights saves even more.

Replace fluorescent magnetic ballasts with electronic ones.

For long-tube fluorescent lighting (as opposed to screw-in compact fluorescents), an old-style magnetic ballast might use 100W to power two 40W tubes, while an electronic ballast might use only 60W. Also, the electronic ballast eliminates flicker and usually eliminates hum. They also generate less heat, which saves additional money on cooling.

Install a skylight.

Using natural lighting saves a bunch of energy and produces a much nicer environment besides. Modern skylights are available which let in only the light and not the heat.

Use solar or LED landscape lighting

Replacing your old landscape lighting with solar or LED can save a significant amount of money. Don't be fooled into thinking your existing lights are low-energy just because they're "low-voltage". A low-voltage system uses the same amount of energy as a high-voltage system, since it's the watt-hours you get charged for, not the volts.
Solar lights are great, but absolutely buy a model with a warranty. Many of the cheap solar landscape lights on the market now last only a year or so before either the solar panel or the rechargable batteries wear out and the lights are useless

Michael Bluejay - Saving Electricity
Future Light - LED Costs
PicknPay - CFL and Incandescent Costs

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