> Space required during initial import: multiply the dump file by 8. For example, for English Wikipedia, the dump size is 10 GB. You should at least have 80 GB space free for the import process
> Space required when completed: multiply the dump file by 2.5. For example, for English Wikipedia, the dump size is 10 GB. When done, your English Wikipedia will be 25 GB.
Ouch, looks like I won't be trying this here any time soon.
You can try the low-space import. There are instructions in XOWA at home/wiki/Help:Options/Import. It takes longer (8-10 hours) but only needs 35 - 40 GB. (which is still a lot).
In the end, you're still going to need about 25 GB for English Wikipedia. If you want something smaller, you can try one of the other wikis (for example, Wiktionary, Wikiquote, Wikisource, etc.) Each of these are generally about 5 GB.
If you don't need the "with images" option, have a look at Aard Dictionary [1], the precompiled english Wikipedia has around 8GB at the moment. It has an app for android also.
You could try the version without images from Kiwix. I keep it on my MacBook (and also at work) to save Internet trips and for when out and about with no access.
EDIT: Just read further down the comments and noticed the mention of Kiwix, apologies for the duplication.
> Space required when completed: multiply the dump file by 2.5. For example, for English Wikipedia, the dump size is 10 GB. When done, your English Wikipedia will be 25 GB.
Ouch, looks like I won't be trying this here any time soon.