The main reason to go to any new light source is efficiency in the life of the source. The most efficient light source is Fiber optic from sunlight but retrofit is highly expensive

Second most effective is a thermal protected Skylight source of light

In Electrical light, The Light Emitting Diode (LED) is the most cost efficient source of light it has less pollution in it s use its life time and at the end of its life it does not leave mercury vapor phosphors in landfills for ground water pollution

That is the main argument it uses 1/5 the power to produce light it is instant On light can be placed in convenient locations as task light or general backup lighting with low power consumption.

Take Kentucky's Savings with Brite LED Traffic lights the changing of those lights paid for themselves in under 1 year now the cost of operation is minimal.

Another city that is changing the Street Lights to LED lighting is in North Carolina not only modern Look but clean bright lighs.