Ah, but that is based on some really inefficient lighting, my friend. Arrays of LEDs can be lit at generally 5% or so of the energy cost of a halogen light providing a similar amount of available energy for the plant to use in photosynthesis. Most of the energy grow lights put out isn't actually used, as it is too far in the infrared, IIRC.
So really, instead of your 1.3KW grow light (which would be a bank of 2 600W High Pressure Sodium, or Metal Halide lamps maybe?) you would just need an array of a few hundred red and blue LEDs, each sucking 0.1 watt or so and putting out light with a much sharper wavelength peak near the chlorophyll absorbance maxima. Oh, BTW, the lifespan of LEDs tends to be considerably greater, which would also make it a more likely candidate, considering how far any replacement bulbs would have to travel..
Plus, by having the ability to control the relative ratio of red and blue light, one can be better in control of the physical characteristics of the plant, allowing for some short bushy plants or some tall gangly ones based on whatever space may be available.