LED cost effectiveness is light years ahead

By September 15, 2017Energy Partners Knowledge Base

Converting your home’s downlights to LED is the first real step to optimising its energy consumption

Many households don’t realise that the lighting in their homes can consume up to 30% of their home’s total usage. That is quite a substantial figure for a feature that we hardly consider and in fact take mostly for granted. This is why lighting is often an overlooked aspect of home energy optimisation: water heating, large appliances and other obvious energy consumers like swimming pool pumps are more often than not given priority by homeowners. However, converting your current downlights to Light Emitting Diodes (LEDs) should actually be one of the first steps to optimising your home’s energy consumption.

LEDs are ideal replacements for traditional incandescent and halogen downlights (the majority of bulb types in South African homes), and are far more cost efficient in the long-term. Unlike conventional light fittings, LEDs create light through electroluminescence – a characteristic of certain elementary materials to emit light when an electric current is passed through them. This process is extremely efficient at turning electric energy into light, whereas other technologies waste a lot of energy through heat (this is actually why conventional fittings feel hot to the touch while in operation, and why LEDs do not). In fact, incandescent bulbs are the least energy efficient, converting about 90% of the energy they use into heat, and only about 10% into actual light.

When to switch off: The dark side of energy saving

The households that are aware of this wastage tend to employ various tactics in an attempt to curb it, such as switching off lights when leaving a room. Even if it is done with noble intention, it is not the best way forward. Analysing when it is or is not most cost effective and efficient to switch a light off is far more complicated than one might think. Firstly, it depends on what the price of electricity is at the time; and secondly, it depends on what kind of bulb we are talking about. This is because light bulbs have a nominal or operational life, which is dependent on how often they are switched off and on.

Bulbs2edt

We have already discussed the inefficiency of incandescent bulbs, and as they waste so much electricity generating heat rather than light, whenever they are not needed, should always then be switched off. Halogen lighting, although more efficient, still uses the wasteful heating technology of incandescent bulbs and so should also be switched off while not needed. Compact fluorescent lamps (CFLs) are slightly more complicated as they are more efficient than the aforementioned bulb types, but their operating life is determined by being switched on and off. Therefore the general rule of thumb is to switch them off only if you plan to leave the room for an amount of time greater than fifteen minutes. In stark contrast, the operating life of an LED bulb is unaffected by turning it on and off.

How to choose the right bulb

The benefits of LEDs extend far beyond their efficiency though. Aesthetically, there are two important factors to note when changing from traditional light fittings to LED: colour appearance and dimmer compatibility. Traditional bulbs produce a warm, almost yellow light—measured on a scale called the Correlated Colour Temperature (CCT) scale they typically range from 2800k to 3400k. Traditional LEDs have a brighter, almost bluish-white in appearance, with a CCT of 5000k—which can appear harsh. However, the latest LEDs are available in a full range of colour tones and can easily replicate exactly the light quality that you require.

Light Spectrum

Many households now feature dimmer switches controlling their lighting. But traditional dimmer switches may not be compatible with LEDs because they draw such a low load. And so if you currently have dimmers on your downlights, you may need to upgrade your dimmer switches as well. However, this is a nominal cost compared to the money you save on energy. LEDs have been fashioned into a full range of fittings that can replace just about any type of traditional light, without requiring extensive rewiring. A conventional halogen downlight drawing 50W can be replaced with a 5W LED—reducing it to just 1/10 of the energy consumption—and provide equivalent light levels.

Probably the most under acknowledged feature of LEDs is that they have a short payback period and offer an excellent return on investment (if good quality fittings are used). The cost and savings will obviously depend on how long you run your lights, as well as the number and types of fittings in your home; these might be using outdated and inefficient transformers, which draw far more electricity than is necessary. In this case, both the bulbs and fittings would need to be replaced. The figures shown in the graph below are for a large home with ~50 LED downlights and typical usage.

LED Graph

EPHS

Author EPHS

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