8 shield gens and I have yet to see anything get through, I'll probably add two more when i start playing on servers, it's got a power load of 400k and a recharge rate of around 50000 per second, and the engines are stuff lol
also the turrets like to have pissing matches, I'm working on fixing this but it looks like the only way I'm gonna fix it is by elevating the tower turrets even higher :(