In a recent article, I referred to a bicycle as an invention that has been around for more than a 100 years. It is still essentially the same – and that was a good thing. There is another invention that has been around for the same length of time – but that is not so good. It’s the humble incandescent bulb.
Till fairly recently it has been the primary source of electric light. However, over the last few years, other options have emerged – namely Compact Fluorescent Lights (CFL) and Light Emitting Diode(LED) bulbs. The question then arises – should one switch to using the other types of bulbs? The aim of this article is to analyse the numbers in order to see what is the best option. The quick answer is that LED bulbs are clearly the best, but if you would like a more detailed explanation, read on.
A little bit of history
The invention of the bulb is usually attributed to Thomas Edison and Joseph Swan – but was actually done before them by several other people. However, they were the first to commercialise them. Edison and Swan’s early bulbs used carbon filaments. The bulb in more or less its current form, with tungsten filaments, was invented by the Hungarian Sandor Just and Croatian Franjo Hanaman in 1904 – a 110 years ago.
Perhaps because they were cheap and electricity was not too expensive and plentiful in the West, no substantial changes were made in the design of the bulb for several decades. It’s a bit shocking when you think about it – the bulb in its current form existed before the car, radio, TV, airplane and any other form of technology that is commonplace today!
The fluorescent light has been around for quite a while, invented in the late 1890s by a gentleman named Peter Cooper Hewitt. The CFL was invented by Edward E. Hammer, an engineer working with GE, around 1973. However, it was only after 1995 that they became commercially available and started being used on a larger scale. In many countries the sale of incandescent bulbs has been banned, thanks to the availability of cheap CFLs.
The red LED was invented by Nick Holonyak Jr. in 1962, while working as a consultant scientist for GE. Prophetically, in an article in the Readers Digest in 1963 itself, he predicted that LED bulbs would replace incandescent bulbs. So while Edison – though he is known for it – did not invent the light bulb, the company he founded, which made him a very rich man, has played an important role in the development of bulbs ever since.
The problem with incandescent bulbs
Incandescent bulbs are bad from many angles. They are inefficient: as is evident to anyone who has tried to study using a 60W bulb in the summer, much of the energy is released in the form of heat. So especially in here in India, where heat is a problem, it is not a good thing. They do not last very long – most burn out within a year. The primary reason that they are still popular is that they are cheap to make and buy.
Let us compare both the advantages and disadvantages. The primary advantage of the incandescent bulb is that it is cheap to buy. But in the long run that is certainly not the case. For the purposes of simplicity of calculation, we assume that the average house has around 20 bulbs of 60W or equivalent and the cost of electricity is around Rs 5 per unit. Further, we assume that these 20 lights are on for about 3 hours per night.
- Incandescent Bulb: A 60W incandescent bulb running for an hour uses .06 Watts – which costs 0.06 X 5 =.3 rupees per hour, or 30 paise per hour. Assuming that it is on for 3 hours a night, it costs around 90 paise per day – or 90×30= Rs. 27 per month! Assuming that it lasts a year and costs around Rs. 12 per bulb, the cost per year is 12 x Rs. 27 + Rs. 12 = Rs. 336.
- CFL Bulb: The equivalent of a 60W bulb is a 11W CFL bulb. Making the same assumptions, the cost per month would be 11/60 x (cost of the incandescent per month) = Rs. 4.95 per month. Or per year, it will cost Rs. 59.4. Adding to this the cost of a CFL bulb, which is around Rs. 150, and assuming it lasts for three years, the cost of using a CFL bulb is Rs. 59.5 + Rs. 50 = Rs. 109.5 per year – or a third of the cost of an incandescent bulb!
- LED Bulb: The equivalent of a 60W incandescent bulb, or a 11W CFL bulb, is a 6W LED bulb. With the same assumptions the bulb will use 0.006W per hour. Hence the cost per day is around 9 paise per day or Rs. 2.70 per month. Or Rs. 32.40 per year. The cost of an LED bulb is around Rs. 600 now – but it is supposed to last 20 years. Assuming it lasts 10 instead of the claimed 20, it costs around Rs. 60 per year. Hence the total cost of running an LED is Rs.60 + Rs.32.40 = Rs.92.40 per year.
Hence if you replace an incandescent bulb with an LED bulb, you will recover the initial cost in two years! For a CFL bulb, it will take a little longer – around six years. A more detailed analysis, of cost per lumen in the US, can be found here: https://en.wikipedia.org/wiki/LED\_lamp.
CFL vs LED
The analysis shows that CFLs and LEDs have pretty much the same running cost per year. However, there are many reasons why LED bulbs are much better than CFL, so are perhaps worth the extra cost.
- Since they consume half the energy, they put less of a drain on the electricity grid. In India we have a tremendous shortage of electricity so whatever one can do to reduce consumption is good.
- Nowadays, many people in Bangalore have an inverter. Typically, one can run 4 or 5 incandescent bulbs for a couple of hours. With the same inverter, one can run LED lights for the lights will run for much longer on it – in this case, around 20 hours!
- CFL bulbs are not very environmentally friendly – they contain mercury and have to be disposed off carefully. They are quite delicate and break easily. They are supposed to last three years or so but quite often do not last so long. LED lights are supposed to last 20 years without substantial degradation, so the environmental impact is much less.
- Over time CFLs degrade substantially. Often, one of the filaments burns out and this results in a reduction of intensity of light.
- Another issue with CFLs is the quality of light. It does not have all the frequencies that the light from an incandescent bulb has – so some things look different. This might be a problem with LEDs as well but is more easily addressed.
- CFL bulbs can not be dimmed so you cannot regulate the light very well.
- LED lights, on the other hand, are very versatile. Pretty much anything is possible with LEDs. Since the bulbs themselves are very small, they can be made in all kinds of shapes and colours. There now exist LEDs whose colour can be varied and adjusted by a smartphone app. So one can have different colours of lights for different times or moods. You can also program them to turn on or off at certain times of the day.
Light can promote peace!
One cannot underestimate the importance of light. Apart from the obvious practical benefits of being able to function in the dark light has tremendous influence on our psychological state. High intensity light exposure is the treatment for people who suffer from Seasonal Affect Disorder – depression caused by lack of exposure to sunlight. Jet Lag can be treated by regulating light exposure.
So the lights you put in your house can have a significant influence on your life. In fact, in Los Angeles, some Sodium vapour streetlights were replaced by LED lights. Apart from a tremendous reduction in maintenance costs and energy savings an unexpected side benefit was a significant drop in crime in that area!
While I am advocating running out and replacing all your incandescent bulbs with LED bulbs I am not quite suggesting running out and replacing all your CFL bulbs with LEDs since that would not be environmentally friendly. However, every time a bulb goes bust in your house, I recommend that you replace it with an LED equivalent. You will save yourself a lot of money in the long run and do your bit for saving the planet.
The cost of an LED bulb may seem to be high – but as the analysis shows, it is still a better deal in the long run. However, there is even better news. The cost-per-lumen of LED bulbs is supposed to follow Haitz’s Law, which asserts that the cost per lumen will drop by a factor of 10 in a decade. So if you wait a bit, unlike most other things, the price will come down! And, like in the case of computers, you will get a better product.
So, go LED, as soon as possible!