AC DC power inverter for a car.

Whether you’re trying to get power from the sun or need electricity when the power’s out, you’ll need an inverter to make it possible. There are two types of inverters, and picking the right one for your needs is crucial.

What Is an Inverter?

An inverter is a device that can take a Direct Current (DC) power source and convert it into Alternating Current (AC). AC power is what comes out of your wall sockets, so any device designed to plug into the wall expects AC power to function.

An inverter essentially does the opposite of what the power brick for your laptop or smartphone does. Electronic devices like PCs and consoles need DC electricity, so they convert AC power into that using a component known as a rectifier. This is important to remember after we’ve covered the main inverter types.

DC vs. AC Electricity

In case you don’t know the difference between AC and DC power, here’s an optional recap of the basics.

AC power is generated at power stations by devices called alternators. There’s one in your internal combustion car as well. An alternator is like an electrical motor but in reverse.

Cross diagram of a DC generator.

Using steam power, the alternator spins copper wire within a magnetic field. This causes electricity to flow. However, since the copper wire is spinning through both magnetic poles, the direction of the flow flips with each full rotation.

DC power, on the other hand, only flows in one direction. It never changes direction but flows from the negative terminal of a battery or other DC power source to the positive terminal.

As you can see in this diagram, when you plot out AC and DC current polarity, AC power forms a smooth wave. This is known as an AC sinusoidal or “sine” wave.

Diagram illustrating the difference between

An inverter’s job is to reproduce that wave from a DC power source, and there are two answers to this problem.

Modified Sine Inverters Simulate AC Power

A modified sine wave inverter produces an approximation of a real AC sine wave. If you chart it out, it looks like a sine wave at first, but if you look closely, there are jagged stair steps in the waveform as the inverter crudely flips between polarities rather than the smooth wave seen above.

Devices designed to run from an AC power source will all generally run on a modified sine wave. However, they might not work correctly. AC electrical motors in particular shouldn’t be used with modified sine inverters. Since the curve of the wave isn’t smooth, the motor vibrates, builds up heat, and will have a shortened lifespan.

Energizer 100W Modified Sine Wave Car Inverter

This affordable modified sine wave inverter lets you use devices such as laptops that require an AC power source to work, by plugging into your car's 12V power outlet, though it's not suitable for devices with motors such as fridges or fans.

Devices without AC motors tend to work as expected with modified sine wave inverters, and any device with a rectifier cleans up that rough AC wave as it turns it into DC power. So lamps, TVs, and other devices are OK for modified inverter use. The major advantage of modified sine inverters is that they are less expensive than pure sine models.

Pure Sine Inverters Offer the Real Deal

Pure sine inverters are more sophisticated devices that can exactly replicate an AC sine wave from a DC power source. Because of their added complexity, they’ve historically cost a lot more than modified sine inverters. However, their cost has decreased dramatically, making it harder to choose which type is right for you.

BESTEK 300W Pure Sine Wave Car Inverter

This pure sine inverter can create AC power from your car's 12V outlets allowing you to run any AC device, from electronics to fridges.

If you have to run any AC motors, then a pure sine wave system is required. If you want to run your electronics with perfect reliability, a pure sine inverter is highly-recommended. If you never want to worry about whether something will work on your inverter, pure since is the way to go.

Do You Need AC Output?

Remember when we said that lots of your appliances and devices have a power supply that converts AC power into DC power? Well, that conversion isn’t free. Converting from one type of current to the other results in a small but not insignificant power loss as heat. When you plug an AC to DC power brick into an inverter, you go from DC to AC and back to DC again.

This is quite wasteful, so if you have any other choice, it would be best to have a DC to DC power transfer. Many modern inverters, modified or pure sine, offer direct DC output. This can be in the form of USB ports or as barrel-plug DC output like the one that plugs into your laptop. If you can, make use of these and the inverter turns your batteries into one huge power bank.

The 5 Best Power Inverters for Your Car

Best Overall
Ampeak Upgrade 2000W Power Inverter 12V to 110V 17 Safe Protections Inverter LCD Display 3AC Outlets 4.8A Dual USB Ports Cigarette Lighter Car Inverter
Best Value
BESTEK 300W Power Inverter DC 12V to 110V AC Car Inverter with 4.2A Dual USB Car Adapter (Red)
Best Portable
Energizer 500 watts Power Inverter Plus 48 watts via USB Ports, Modified sine Wave car Inverter, 12V to 110 Volts, Two AC outlets, Four USB Ports 2.4A ea - ETL Approved to UL and CSA Standards
Most Compact
BESTEK 150W Car Power Inverter DC 12V to 110V AC Converter, Car Outlet Adapter with AC Outlet and 4.5A Dual USB, Car Plug Adapter Outlet Charger for Laptop Computer
Most Power
Energizer 4000 Watts Power Inverter Modified Sine Wave Car Inverter, 12V to 110 Volts, Two AC Outlets, Two USB Ports (2.4 Amp), Hardwire Kit, Battery Cables Included – ETL Approved Under UL STD 458
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Sydney Butler has over 20 years of experience as a freelance PC technician and system builder. He's worked for more than a decade in user education and spends his time explaining technology to professional, educational, and mainstream audiences. His interests include VR, PC, Mac, gaming, 3D printing, consumer electronics, the web, and privacy. He holds a Master of Arts degree in Research Psychology with a focus on Cyberpsychology in particular.
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