Back-up lighting?

Has anyone considered (or had the need) to have back-up lighting? I live in any area where power-outs are not uncommon and I'm concerned about what will happen if the power goes out while I'm not home. I'd like to know if 12v fluoros would produce enough light in the absence of a HPS so it wouldn't affect the plants in a power-out? Any other ideas? I sorta need a cheap solution so a generator with a auto transfer switch is outta the question...

Barring major disasters, power outages rarely last more than an hour or two, you will probably be ok without a backup system.