I was recently asked this question, so I set about doing some research about what options are available if you need a TV for use on a power outage.
A: Do you mean, an old analog portable - battery operated - TV? The short answer, in most cases, is NO.
However, do have a number of options that will get you TV in an emergency, even when nobody else has power or TV. You can even get that old analog TV to work if you have time (and money) on your hands.
I'm not sure how many of you have survived major - or even minor disasters. One of the first things to happen is - the electric goes out, and you're left with no TV and maybe a portable radio with dead batteries for news and information. Maybe you're thinking, "I have my really super terrific iPad and my cell phone, with all the power of the internet and a cell phone too. I don't need a tv or radio!" Well, you'd be wrong, Bucky. Along with the power, other things that go out in an emergency are wireless internet and cell phone towers. TV and radio stations have backup power, as they are REQUIRED BY LAW for just these sort of situations, unlike cell and wireless internet providers. Just ask anyone who survived 9/11 or Hurricane Katrina!
So, here's the scoop:
First, you may be able to use that old TV, as-is, "IF": "If" you have cable, and "if" your cable company still provides analog cable, and "if" you still have cable at all when the power is out. But he chances of having analog cable decrease every day as providers switch to digital, and having cable in a power outage does happen, but you can't count on it. In most cases, you will need a battery powered TV capable of receiving digital signals with an antenna.
If you want to keep your old portable TV and don't have cable, you can get a converter box that has a "wall-wart" power supply, you can make a DC power pack that will power your converter box, or run a cord from your car's lighter socket.. I found a list of converters that take an external power supply here: Additional Features Matrix for DTV Converter Boxes. You can search Amazon for converter boxes here: Search Amazon for DTV converter boxes.
Here is a guide to powering an Artec t3a Pro converter box from a car: RVs and Converter Boxes, however, since it's a 12v converter box, I really don't know why they used a $25 universal adapter, the Enercell Universal DC Power Adapter : Car Adapters | From RadioShack.com , since just wiring from 12v to a $3 type M plug from Radio Shack Size M Coaxial DC Power Plug (2-Pack) - RadioShack.com would work. Here's a link to the Artec converter on Amazon: Artec T3a Pro
I also have a laptop with a USB stick DTV tuner that works great, this is a very good solution since it has a pretty big screen compared to a portable TV.
RCA 7" Portable TV
Another option if you already have a small 17 inch or less flat panel DTV is a POWER INVERTER that converts 12 volts DC into 120 volts AC. Typically, they plug in to your car's lighter plug, and then you can run an extension cord to your small digital TV. Make sure you get one that will provide more power than your TV requires, as they are great for powering and charging other devices. I once powered a 13" CRT, CFL lights, and a fan (to move heat) during an ice storm in upstate NY. My neighbors were envious!
Another potential solution: there is a new standard for MOBILE DTV (MDTV) that can be used while moving. It's just being introduced in major markets around the US, but you may want to wait until more mobile DTV devices are available (It may even be available in cell phones, but don't hold your breath. Cell providers hate to include features that don't make them money!) Here's a few mobile DTV devices that ARE available now- Search Amazon.com for mobile dtv.
Whatever TV solution you choose for an emergency, or while camping or at the beach, beware: all those little bitty antennas that come with portable TVs and USB tuner sticks are useless unless you live in a place with strong signals. Get yourself a better antenna, or make your own. Just make sure it's not an amplified antenna, or you'll have yet another device to provide power for! And while you have power and lights, set up your emergency TV and make sure it all works properly. As in, do it NOW!
As the Boy Scouts say: "Be Prepared!"