garbon2535 said:Several HOURS is right.
It depends on your needs, really...for instance, in the 21 years I have lived here in Calgary, I have not had a power-cut that lasted longer then 2 minutes, and outages longer than 3-4 hours are unheard of in this city, so something like this would more than meet my needs, and if a person waited a couple of hours before using it, it could get you easily through a 12-16 hour outage, and would run you a bare $200.
It would make more sense to purchase a gas generator. As long as you keep filling it with gas it will run.
A good option for someone with the threat of 24+ hour outages, and about $1000-$1500 to spend.