Quote Originally Posted by alg View Post
No no no. Don't get me wrong. Electronics ballast need up to 40W to use together with a 36W FL tube. Good thing abt e-ballast is it will not shorten the lifespan of the FL tube as during startup, the light tube will not flicker.

Only LED uses less than 18W in this case comparing the same specs light tube.
electronic ballast does not consume 40W. an electronic ballast with 40W on it means that the ballast can be used to drive light tubes with ratings up to 40W

a FL or PL tube radiates light in 360 deg around the tube.
a LED radiates light in the frontal 180 deg.
if all things are equal, both the 36W FL/PL tube and 18W LED will 'throw' identical amount of light in a particular direction. without a reflector, 1/2 of the FL/PL light is lost.