A guy is setting up a large-scale LED vegetable farm in Alaska, where getting fresh produce in the winter is quite expensive, since of course it has to be shipped in by a fairly fast (= costly) method. See:

http://www.adn.com/article/20150315/vertical-farm-poised-ris...

I actually built an experimental LED grow light for a friend several years ago, back before legalization. She was not particularly worried about getting busted, but reducing the cost of electricity was a really big deal, since power and rent defined the cost of business. The system was a few years ahead of its time, as LED emitters were not yet powerful enough to replace her high-pressure sodium lamps, but it worked well for getting her new clones started. Beyond the simple efficiency of LEDs as light producers, the fact that we didn't have to waste any power generating yellow-green light meant the power requirement was something like 10% of what it had been with HPS. Clorophyll absorption peaks are at 430nm and 662nm, so we used LEDs with peak wavelengths near those values, and while the light appeared dim and purple to human eyes, the plants loved it.

Fruit and nuts are probably not going to see this sort of thing, primarily because the trees take a very long time to come to maturity. With some varieties you might be looking at a decade of care before you actually get any yield from them at all.