I think it's suppose to be close to 17gbs if you get the digital version.
There is no install with the retail copy. No Wii U games do that. Not needed since the disc drive reads faster then the one in the PS3 and it holds more data then the 360 discs since the Wii U disc are a version of blu-ray. Now the game will patch and that patch data will be saved to the system's storage but that shouldn't be large at all.
Thanks so much, I'm getting the Wii U basic version for christmas and want to get this game. I really don't play a lot of games and I don't download games and am very pro disc. The basic version will satisfy my needs just fine.
You can buy an external hard drive (it needs to have its own power source via plug into a wall) and get either a 1TB or 2TB one here on amazon, and it doesn't cost much. You will want one that has a 2.0 usb, as I think the Wii U only works with 2.0 USB, but if you want double check that on the internet. If a 3.0 USB speed works, than get that, but if the 2.0 USB speed is the one that works, get that, if the external hard drive is compitable with 2.0, than that works too. It's much cheaper going the route of getting an external hard drive for extra space.