COMPARING LIGHT BULB EFFICIENCIES OR THE MONEY YOU WASTE ON HEAT
Every electricity bill, you pay for your lights. It can be a good chunk of the total cost, as we have shown in our previous article. Yet paying for lights most often does not equal to paying for lighting. One would think that a light bulb is there to create light, but in reality – the main output is unrequested heat. Heat which makes your room stuffy, your working space too hot, and most importantly – consumes your electricity dollars for something you don’t need. It’s called light bulb efficiency – how much light does a bulb produce in comparison to heat. Luckily, different light bulb types have different efficiencies.
Well, to be honest that was a little bit of an overstatement – all light bulbs have very similar efficiencies, including the energy-saving (fluorescent) bulb, except for the LED. Take a look at the graphs presented showing light bulb efficiencies for fluorescent, incandescent, and halogen lights.
96% of energy is wasted on heat; only 4% of energy is spent on making light. That means that out of every $100 you pay for your light, in reality $96 goes to heating the light bulb. Only $4/$100 go towards the required purpose.
Incandescent is even worse than fluorescent. 98% of the energy is wasted on heat; only 2% is spent on making light. Out of every $100 you pay for light, only $2 is spent on lighting. $98 is spent on a by-product of producing that lighting.
Halogen bulbs aren’t that good either. They fit in between incandescent and fluorescent, spending 3% of their incoming energy on light. The remaining 97% go to heating up your working space or the ceiling. $3/$100 you pay go towards producing light.
As you can see, all of the light bulbs presented above produce heat rather than light. That heat is either completely wasteful or sometimes even uncomfortable. Either way – it represents wasted money. The picture drastically changes when we look at the efficiency of LEDs.
For the first time, most of the graph is colored yellow. Moreover, LED lights are almost the exact opposite of all the others – they are the only ones spending over 90% of their input energy on light instead of heat. That means that out of every $100, $91/$100 go on producing light. Only $9 goes towards heat. Does that mean that LED shines almost ten times as bright? No. While LEDs are slightly brighter, the rest of the difference is made up by consuming less total energy (they require less energy because they do not need any to produce heat).
It isn’t hard to spot the leader. It isn’t hard to spot what wastes your money and what uses it. However, there is yet another way of presenting this difference. So far, we have only considered percentages. Now, we will translate it into dollars.
A number of simple assumptions have to be made about the average household. While these parameters differ from household to household, the trends and the differences between lighting types apply to all. These average household parameters are: an average household has 30 light bulbs, uses light for 6 hours a day, mostly during off-peak hours, and pays Ontario off-peak prices of 6.5 cents/kWhr.
Using the assumptions above, we can plot the following relation:
This graph shows the spending on heat out of that total amount you pay for lighting. It can be seen that after 5 years, as much as $1000 has been wasted on heating the light bulbs if you use incandescent or halogen sources of light. Energy-saving indeed spend less on heat than those two, but from the very beginning they are already worse off than LED. This chart provides cumulative data over the years. Those years are already counting if you are not using LED.
The choice is yours, the money are yours. In our opinion, the money you pay for light – should pay for light. If you agree, then we hope you will consider LED as your lighting source. It consumes less energy and it spends energy right. More than what we could say for halogen, incandescent, or energy-saving bulbs. Make the right choice – choose LED!