Check out vertical farms (skyscrapers converted to farms) the yields are higher for much less space. There are multiple farms in the silo. If it takes over a day to traverse from the top to lowest level there’s no way having just one farm would be able to keep up. Probably multiple kitchens and dining areas too.
Everything I’ve seen gives it a range between 25% and 96% depending on several factors. It seems like we’re still getting this all figured out and it’s early but if we can get closer to that upper limit it will make a huge difference when considering the impact of these batteries.