The real deal with bike locks is, buy enough lock to feel secure.Probably 90 percent of the time even a cable is enough, unless you park at a busy rack on a college campus. The rest of the time nothing is enough. Use enough lock/chain/cable to let you have peace of mind while you are doing whatever, then come back and get your bike.
Except for very rare occurrences, if you have half a brain you know when and where you can lock your bike.
Flip side: One guy on this site had his bike stolen out of his apartment. Guy broke in and grabbed his ride, while he was home, as I recall.
So .... how big a lock do you use at home?