The point is: Does it make any sense to grow a tree under artificial light? Furthermore, is there a real advantage in growing a tree without soil? The usual greenhouse is usually good enough to grow citrics, and a little extra light and temperature control might be all you need.
As a rule, the vegetables which are grown for their leaves (aromatic plants, lettuces, etc.) can be grown in a relatively short period of time, thus with a moderate energy bill, fruit vegetables can take a significant amount of space and energy to yield a moderate harvest.
As far as I have read, radish might be the shortest vegetable to grow (about 4 weeks under standard conditions , i.e. on soil and outdoors, climate permitirng).
I am a newcomer to hydroponics, but from what I've read here and there, there is huge difference in resources demanded by diferent plants. If cost is an issue, carefull selection of plants and cultivars can make a huge difference.
Is there any statistics in cost per kilo/pound of different plants (regarding to energy, nutrients, etc) ?
Disclaimer; Not only am I a newcomer, I am also Spanish, so my English may contain more mistakes than the average. Sorry for thalt.