If you want my kind of expertise - aka "An Expert is a former drip, now under pressure" here it is.
I run Answer Center a 24/7 answering service and off-site receptionist service and we've got a UPS that will keep about 20 computers, lights and fans going for up to 4 hours after we lose power. It takes 8 batteries that weigh about 70 lbs each. We've been in business for 27 years and our first computers were an Apple 2-C and a Tandy HD-6000 (affectionately known as "the son of the trash-80")... That sucker was so old it actually had an 8.5 inch floppy drive.
Because we answer for medical and hazmat companies, we cannot go down. Interestingly, during Hurricane Isabel we stayed up and functioning while the 911 rooms for both Virginia Beach and Hampton closed! (still snickering... woosies!)
We back up the UPS with a Honda EB-11000 gasoline generator that weighs 405 lbs empty and is 34.5 inches wide on it's wheels - so that we can pull it out through the front door before we start it up. Our generator feeds back into our operations room via a large battery charger and the UPS which takes out any current fluctuations that the Honda doesn't clear itself.
A UPS for your laptop really isn't necessary. Pull the plug and it will go to it's battery without a hitch. For a desktop business model, you've gotta have one or you will go down hard in a power failure. For about anything else that draws current, especially a microwave or a refrigerator I wouldn't even rely on a UPS. The high draw will drain one down VERY fast -in 5 to 10 minutes in fact. And what's the worst that can happen if your popcorn stops popping?
If you want to carry a generator of sufficient size you can restart your microwave or refrig. without trouble or losses.
Most small UPS (uninterruptible power supplies) are designed to protect only critical systems like computers which don't draw much current, presuming you have a flat screen, not an old CRT. The downside to a UPS that a lot of people don't realize is that the battery life is pretty limited, the batteries are expensive and heavy, and if you have them inside you need the gel ones that don't off gas acid fumes.
I've gone into many businesses and found UPS's with batteries that are dust dry and have been dead for years without anyone knowing it. You've got to check your batteries at least once every six months, and you can count on needing new ones every two years. It rarely happens, but if a battery discharges completely it can actually explode. We had a friend in the answering service business who had a "no host weenie roast" at his service when a battery exploded and started a fire in his computer room! He was down for almost 72 hours - and got back up that fast only because his system vendor moved heaven and earth to get him replacement equipment and emergency downloading of data from his fried hard drives.
If you are using a computer for recreation and communication rather than for your business, the worst thing that can happen is that you lose power in the middle of a long e-mail and lose every precious word you've typed. Long e-mail?
Data loss is the big bugaboo during a power loss, doing regular backups of your data is probably more important than having a UPS. Also test your backups to make sure they will reload AND keep more than one. We keep seven days rolling PLUS an end-of-month backup that goes back two years.
Even for a home computer have at least one off-site backup. If your house burns and your backup disk sits next to your computer....
Simply backing up to a flash drive, CD or DVD regularly and putting it in your car, or your Airstream, etc is a lifesaver.
Most small under the desk UPS's are really designed to let you do an orderly shutdown in a blackout or get you through a momentary outage.
The most important thing you can do about prolonged power outages is think, plan and practice for them. We do a generator drill once a month. How will we refill the generator if all of the power is out for 10 days and the gas stations don't have working pumps? Well, we do have 100 gallons in gerry cans and we were confident that we could siphon from our cars until someone here told me about the anti-siphon devices in new cars.... so we've now bought some extra cans and may bury a tank in the back yard. I have customers who maintain gas station equipment so maybe they could help us by manually pumping gas up from a station's tanks.
Long and short - space and weight are at a premium in our Airstreams. Carry a generator if you want, but rely on common sense before you just start loading stuff in that doesn't serve any real purpose but takes up that space and weight. How many people lived in their Airstreams for weeks or months after Katrina. How many had the sense to hitch up and head north as it was getting ready to hit?