There is a love affair that most people have with the familiar incandescent light bulb, also known as the tungsten. It delights us with its cosy agreeable light and atmosphere, soft on the eye, warm on the heart. We love it, but we have never realised it. Until now when we might lose it. With this traditional light bulb we know what to expect, we know where to use it and don't mind buying one at an inexpensive R4.50.

Apart from this, what else does it really do for us?

In the half year that this tungsten delights us in our home it will probably have clocked up 10 times its purchase value on our electricity bill: A 60W light bulb burning only 3 hours per day over ½ year consumes 32.4k Wh. Combined with the new electricity tariff of R1.34, typical for a middle income household, the energy costs are R44 to the homeowner.

To the planet the costs are 33.7 kg of carbon dioxide emissions into the atmosphere. Can you imagine what the 8 down-lighters (50 W each) above the dining table consume and pollute over ½ year? Yep, they cost the homeowner R294 in electricity and cause 227 kg of CO2. The reasons for the high running and environmental costs, is that all tungsten and halogen light bulbs convert 80-90% of the energy consumed into HEAT, and only the rest into visible light!

high cost for the environment

Mmh ' high cost for us, high cost for the environment, not really in our favour, is it? It appears to be a rather one-sided love relationship with an unsustainable future' Maybe it is time to say good-bye to the good old incandescent and embrace what is new, more efficient and thus green. Generally, where there is a door closing, there is another opening. What lies beyond that door is a challenge for us to explore more efficient options and to reconsider where and how we use light.

Many of us have heard of CFLs (compact fluorescent) and LEDs (light emitting diodes). I aware that some of them have their drawbacks and that they will challenge our perception on what light should look like and how much a light bulb should cost. But on the other hand, since most of us have tried our very first CFL  and decided promptly that this was not for us, the industry has moved on to give us more agreeable shades of warm light colours and better looking shapes and sizes. Some of them are now dimmable and suitable for outdoors.

LED

CFL

So, the industry has moved on and it is time for us to move on, too.  We need to balance the qualities of a light fitting and its bulbs carefully. Light bulb buying won't be as easy as choosing between 25W to 100W any longer and herein lies our challenge. We need to consider these 5 aspects of light quality first and then make an informed choice:

Watt

Watt (W) is the energy a light bulb consumes. CFL light bulbs for residential purposes generally range from as little as 7W to as much as 14W. (Roughly, a 7W CFL replaces a 40W incandescent, a 11W a 60W, and a 14W a 100W bulb). LED light bulbs can run on as little as 1 or 2Watts, stronger and extra bright ones use up to 14W. Compared to the old tungsten, any CFL or LED will often save us more than 80% in electricity and thus pay itself back over time. Generally the principal of 'the more Watt the brighter the bulb' applies. That said one has to watch out for the quality of the bulb and ensure that the Watt consumption is in line with the expected lumen output.

Too much lumen not good

Lumen (lm) is the light emitted as perceived by the human eye. In the specifications of a good quality light bulb you should find a Lumen figure. Lumen is closely related to the task we would like to perform under that light:

Tasks that require good eyesight such as reading, cutting or office work would require a minimum of 300lm, preferably 400 to 500lm, whereas general lighting for a corridor or bedroom can do with less than that.

Lumen might also matter as one switches on the light. CFLs take up to 2 minutes to develop their full lumen potential, whereas LEDs are instantly bright. Over-illumination, ie too much lumen throughout the room, is a widespread condition in homes. I have seen rooms where one could repair a watch in every corner of that room. Artificial illumination levels are often higher at night than natural illumination during the day. We have to ask ourselves whether this is what we need?

Reducing over-illumination is not only helping the environment and your pocket but also your sleep. You'll probably find that you and your children have less trouble falling asleep as less light in the eyes triggers chemical changes in human bodies, which aid sleep.

Do you need warm or cold light?

Colour temperature (K) is measured in Kelvin and ranges from 2500 to 4000K for residential purposes. The lower the figure is in Kelvin, the warmer the colour. A quality light bulb will state the colour temperature in the specification on the box. It is a personal decision which colour suits which purposes in your home or office. I would recommend cooler lights for storerooms, pantries, home offices, corridors and bathrooms.

It is easier to find brighter and cooler light bulbs and often these are cheaper, too. So when you can make do with it, it often is the less expensive choice. For living areas where comfort and cosiness matter, warmer colours of 3000K or lower would be more appropriate. Combining cool with warm light bulbs in one and the same room, or on one and the same chandelier even, is sometimes a way of getting high lumen mixed with warm yellow light.

One might also bring the warmth back through a candle or oil lamp fuelled by natural and renewable resources such as Citronella oil, soy oil or beeswax.

How transparent is your light fitting?

Luminaire housing is the trade's term for lampshade, i.e. the form and transparency of a light fitting. Its design determines the light output. Glass or frosted glass retains only a tiny amount of the light emitted, whereas an opaque lampshade such as a metal or dark fabric one would keep a considerable amount inside the luminaire housing.

Up-lighters for instance retain around 40% in the lampshade bowl and throw the rest of the light up onto the ceiling, creating a lovely effect. Yet they do not yield much light to work with for the person below.

Ideally a luminaire housing would pass on all light emitted by the bulb and avoid any obstructions to the stream of light. This of course saves us energy.

What is the purpose?

Each light has a purpose. At night we need light to work on a desk, to feel safe at home, to give us a sense of space, like in an open plan living room, and to move around the home.

Grandma's chandelier above our lounge coffee table with its beautiful effect of royal grandeur pulls a considerable 8x40W= 320W at any moment. It brightens our entire lounge when all we do is read a book in the corner of the sofa. Now we don't have light to read the book by,  as the chandelier lights up the whole room. A good solution would be to have an extra standing lamp with an LED spotlight (3W) right next to the sofa, and for the overall room a central pendant fitted with one LED pear (5W).

Purposes vary, you should be very clear on what you need the light for. Here are questions to ask:

• How many hours a day would this light be operating?
• What is it needed for?
• What are the tasks that will be performed under that light?
• Does it need to be dimmable?
• Is the lampshade in a space that experiences moisture? (Spaces such as outdoor areas or bathroom light fittings)

The above 5 aspect are interrelated.

say goodbye to incandescents

So, when you are ready to say good bye to your incandescent light bulbs and keen to explore new options, equip yourself with a list of your light fittings and their 5 aspects.

You'll probably find that gradual change is more agreeable. Changing all the light bulbs from one day to the next will likely be a bit of a shock to your eyes, as well as your budget. If your home transforms over time, your family will have time to adapt and to understand the 5 aspects much better. This way you will also discover which new bulb works for you and your style.

Get to your local electrical shop or DIY warehouse to see what's available. Don't be shy to ask them for their LED or CFL catalogue. Maybe the bulbs specific to your needs can be ordered. Also remember that a well chosen energy efficient light bulb will pay itself off over the next months or year.

And for those who feel overwhelmed by the new light bulb choices, or who simply do not have the time to familiarise themves with it, there is help available. An eco consultant like myself would love to assist you in minimizing your electricity bill and environmental impact. I can help you make the right kind of light bulb choice that suits your needs, your individual circumstances and budget.

About the author

Martina Gluckman (pictured, top) is a residential eco auditor and an expert in turning existing homes into energy and water efficient households whereby substantial savings on utility bills and carbon emissions can be achieved. She teaches residential eco-auditing through environmental education leader Global Carbon Exchange. Her company 'Tiptoe ' leave no footprint' is an eco consultancy which specialises in the residential sector offering energy, water and eco audits. The service is designed to help identify and eliminate inefficiencies in a home, and promote change to a greener more sustainable lifestyle for the owner.

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