Those are better than nothing but really the attacker is gonna be all up on you with whatever weapon they brought. Also you will need to make contact with bare skin on say a neck. Contact to a wrist may make them drop whats in that hand. I actually have some of those laying around, had an ex girl friend freaking out trying to beat the shit outta me, I shocked her on the tit with it and it just made her madder. I didn't wannt hit her on the neck or face but the way she was acting I should have. The one I used was more like 80 bucks, high grade supposedly.
Also remember when in close quarters combat, your weapon can become their weapon unless you are really good with it. If facing multiple attackers without some sorta ninja skills or a gun you are likely fucked.
Fortify the fuck out of that place, pepper spray could be used through a partially opened door but if they have a gun they can shoot through the door. You could get a un-registered firearm, if they break in, and i mean actually break in then you cap their ass and it was their gun they dropped breaking in. Thats the story and nobody should be alive to contradict it.