What is energy efficiency? In smart words – getting the same service with less input of energy. In the field of lighting this statement can be mapped as getting same light using less electricity. This is the latest saga of a long-long journey through ages. When the first light bulbs were invented in 1879 by Edison, the cost of producing electricity was high. But soon, it came down and using electric light became cheaper than traditional oil lamps. That was the mere beginning. Afterwards we got the normal tube lights of 4 feet length, the CFL’s and then the LED’s for domestic usage.
Total amount of emitted light from a source is measured by the unit lumen (lm). And our usage of electricity is measured by the unit watt (w). So, the ratio of lm/w determines the highness or lowness of energy efficiency of a light source.
Say for example, if a 60watt lamp gives 800 lumens and another 10watt lamp gives 400 lumens — then which one has got more energy efficiency?
The TOTAL lumen is not the only factor here; you have to think as ratio, as I wrote. The first 60w lamp is giving 800lm – higher than 400lm, surely. But to produce double quantity of light it is using 6 times energy than the second one.
Now think from the reverse angle. Think, you need 8,000 lumens for your entire apartment. Then if you use the first kind of lamp, you’ll need 10 such (800lm x 10) and you’ll end up burning 600 watts (60w x 10). But if you use the second kind — you need to burn 200 watts (10w x 20), using 20 (400lm x 20) such lamps.
So, your electric bill will be 1/3rd per month by using the second lamp !!!
Prakash LED does this exact thing. If you use a 60w normal lamp (GLS) – you get around 800lm. Similar light you’ll get using a CFL of 12w.