[AngryData]

Modern LED grow lights require minimum 35 watts per square foot to grow things beyond just lettuce, which is around 1.5 million watts per acre. Americans currently consume a bit over 2.5 acres of farmland produce per year, however you could get that down to 1 acre without much problem by cutting out some of the less land efficient crops likes fruit trees, especially when talking indoor grow.

So I would expect bare minimum energy requirements to be near 1.5-2 million watts per person for 12-16 hours a day for indoor food sustainability.

This is of course not accounting for fertilizer which has large energy requirements or anything more than the most simple and basic of climate control.

[yetanotherloser]

wow, if that is all true then vertical farming is even less relevant to this scenario than I thought. I'm not sure I'm qualified to check your figures and I suspect some of your assumptions are more pessimistic than mine, but the fundamentals pass a reality check vs. amount of energy delivered by the sun (lots).

(Just to preempt some likely replies from other people: I'm sure there is a big difference between "Americans consume" (including livestock grazing, which can't be magic-ed into anything else) and "You can get by on" (measured in hypothetical perfect-acres) - it would take esoteric casuistry to make these really comparable anyway. Nevertheless the gap is so large that AngryData's fundamental point is extremely robust: growlamp-ing everyone's basic needs is fantasy-land. I thought that, but didn't realise the case against it was as strong as I now suspect it might be)

[robocat]

> but the fundamentals pass a reality check vs amount of energy delivered by the sun (lots).

  Solar panels produce about 150 watts of energy per square meter since most solar panels operate at 15% efficiency this translates to 15 watts per square foot.

Which is 100 Watts solar energy per square foot, so 35 Watts certainly has the right order. (LEDs are not 100% efficient, sunlight is not 100% efficient with chlorophyll, some edible plants grow in shade).

[TrueSlacker0]

The root scenario is if a large volcanic eruption causes prolonged limited sunlight. So solar isn't the best option in this case.