There are many different factors that you need to take into account to answer this question correctly and accurately. If you compare the total lumen output of conventional lights, such as High Pressure Sodium or Metal Halide, against the lumen output of LED lights, it appears that LEDs deliver less light. These comparisons are not accurate, as they fail to take into account the significant amount of light that is wasted in non-LED Lighting applications.
Lumen output is a poor measure of the suitability of how well a lighting solution performs it’s job. A better measuring stick is how light is delivered, or rather, how much of the light is delivered to a area that needs to be lit. So you must make an accurate comparison on the amount of delivered light, not the amount of available light. If the light cannot be delivered to where it is needed, it is of no value to you.
Several factors come into play, As much as 30% or more of the lumens is lost in a conventional lights delivery. Reflectors, lenses and other factors all reduce lumen output from a normal light source. These lights are radial lights, in the sense that they distribute their light in every direction, and it is the job of reflectors and lenses to collect, redirect and hopefully deliver that light where it is needed. Unfortunately, a lot of usable light is lost in the process.
LED lights, on the other hand, are directional by nature. A well designed LED Light will place and direct all it’s light where it is needed. For example, it makes complete sense for a street light to direct all of its light to the roadway below. LED’s do that by design. The face of a LED Street Light contains all the LED’s, and all the light they produce gets sent down to the roadway. Reflectors are not required.
Secondly, conventional light sources such as Metal Halide and High Pressure Sodium suffer from lumen degradation quickly after initial installation. So although the specifications on initial lumens is very high out of the package, what is not advertised is the expected lumen output 3, 6 or even 12 months later. So it may appear that a conventional light is more bright than LED, conventional wisdom shows lumen output degrades quickly which reduces the amount of light available to perform the task.
In conclusion, when comparing LED against conventional light sources, LEDs often perform as well, and in some cases significantly better, than conventional lighting while consuming far less electricity to perform the job.