1- make a light, tick PRIMARY_OMNI or PRIMARY_SPOT <(i recommend this tho) and tick PRIMARY_SCRIPTABLE
 
2- de-select the light
 
3- right click on 2D view and select info<null
 
4- select the light first, select Null cube and hit W on keyboard
 
5- select the light only and press N to give it some keys and values:-
targetname : light_electric
script_float : desired number
intensity: 0.001
 
now script_float is basically intensity after the power is turned on so you can change script_float like if you are changing intensity
 
 
and you are actually done!