A power inverter converts DC power or direct current to standard AC power or alternating current, which allows you to run electrical equipment off your car or marine battery for mobile applications, emergencies or simple convenience.

Power inverters are small rectangular devices that have a trailing wire with a jack that plugs directly into the cigarette lighter on the dashboard. They might also come with jumper-like cables for connecting directly to a battery. The device normally has one or two outlets for standard electrical cords. Your laptop, small-screen television, video game player or portable DVD theater are all examples of devices that will get you through a long ride, assuming you're not the one driving!

Power inverters are great for camping at parks that do not provide electricity. The toaster, blender, and boom box can all still be used. On your boat you can plug in the digital movie camera to capture those great water-skiing videos you might have missed after the camera's battery ran low!

In a utility outage a power inverter can be used for emergency electricity. Just run an extension cord from your car into the house, or if you have a charged spare battery you can connect the power inverter directly. Plug in a radio to tune into important alerts, run essential medical equipment, lights, or whatever else you need that falls within the inverter's power limits.

Power inverters come in many models that vary in watts. The amount of wattage you will require on yours depends on the total draw of the devices you'd like to use. If you have a two-outlet inverter and will be plugging in 2 devices at once, add up the total wattage of both devices then add at least 50% more to account for peaks or spikes in the power draw. For example if your DVD theater draws 100 watts and your laptop another 100 watts, a minimum 300-watt inverter is recommended.

When using your power inverter continuously inside a vehicle that is not running, the engine should be started at least once an hour for 10-15 minutes to keep the battery from discharging. WARNING: Do not start a vehicle in a closed garage as the carbon monoxide in the exhaust is fatal. Power inverters operate on the assumption that the battery is in good condition and fully charged. A weak battery will be drained easily if demands are too high. This could leave you stranded so be sure to check the battery's condition before using a power inverter in a stationary vehicle.

If the power inverter is being used while the vehicle is running as in the case of a road trip, there should be no problem with the extra draw providing the battery is in good condition.

Power inverters produce one of three different types of wave output:

• Square Wave
• Modified Square Wave (Modified Sine Wave)
• Pure Sine Wave (True Sine Wave)

The three different wave signals represent three different qualities of power output and consequently, three different price categories. Square wave inverters result in uneven power delivery that is not efficient for running most devices. Square wave inverters were the first types of inverters made and are obsolete.

Modified square wave (modified sine wave) inverters deliver power that is consistent and efficient enough to run most devices fine. This type of inverter is probably the most popular.

Pure sine wave inverters are the most expensive, but they also deliver the most consistent wave output. Some sensitive equipment requires a sine wave, like certain medical equipment and variable speed or rechargeable tools. If you aren't sure if the device you want to use requires a pure sine wave or not, call the manufacturer to ask. Or if you don't mind the price difference any device will run on a pure sine wave, whether it requires it or not. The only drawback would be in spending more than you need to for your power inverter.

Always use a power inverter that is rated high enough for the device(s) you are running and avoid adapters that would allow more outlets than the unit is designed to accommodate.

Working with car batteries can be dangerous and can result in serious injury, and improper use of a power inverter can lead to electrocution, so for your own safety be sure to read and follow any and all safety precautions that are listed in your owner's manual, which will come with your power inverter.