@Azriel: living in southern california I used to think the same thing, but for some reason in my current apartment over the past year we've had 4 power outages that lasted 6+ hours
my apt is oddly situated on the hot water line, so its ALWAYS 70F in here, which is kinda nice...but as my collection is growing I need to start preparing for the long run
EDIT: I currently DO use the battery packup plugs for my lights and my computer...but I just don't trust it as a "serious" solution. Trying to find something smaller/not as noisy as a generator, but more consistent than the power strips...
I was imagining a solar battery maybe?
Just an FYI all solar systems are battery based. Just like your battery backup. Battery backup's are referred to in the electronic industry as UPS (Un Interruptable PowerSupply).
If you have not had "consistency" with one then the battery is most likely dead. Most UPS have a warranty of 1 or 2 years. They guarantee to immediately switch to the backup without power loss. Lights don't even flicker.
Some UPS's that you buy at Best Buy or Office max have a VERY small battery. Anything under 550 VA is not even really worth it. 825 VA will keep most lights and small fans etc running for an hour or two. But if you have serious power issues then look on amazon and you can get them up to 2,000VA and lasts for hours.
You can calculate how long it will last if you know the amperage of your devices plugged in. Wattage for lights which in some cases is VA or 120V* the Amperage of the device. Add these up and they must be less than 60% of the UPS VA rating. Otherwise the device wont run long and will likely overload and die immediately.
For example if you had a 200 VA UPS and two 60 watt lights hooked to it then you have 120VA (60 * 2 V*A=watts in most cases). If you look at the chart that comes with your UPS it will tell you how long your UPS will last for I looked at mine and this situation would last about an hour.
I recently used a solar system on a pumpstation at work. It was 2500 VA however cost close to 2 grand and had an 80lb battery.
Just food for thought. I'm an electrical engineer by trade and I love this stuff...almost as much as frogs. Let me know if you have any questions!
Robbie