How to calculate the wattage of a laptop for car power inverter

A car inverter changes power to be usable from you car devices to your house devices Tha iss 12-volt direct current (DC) and changes it to 120-volt alternating current (AC). Once the DC is changed to AC you can run anything that will run off your house power if you have a big enough power inverter to change it.

How big of a power inverter do you need?

That means you need to size your power inverter for the items you will be using. To figure this out make a list of all the items you will be using at the same time. Then you need to find the labels on the electronics or power blender to find the power it uses. Always use the max power to calculate your needs.

For laptops go to the power cord and find the label on the square power adapter. It should give you an output number. My laptop also has the power numbers on the back of the laptop.

laptop power requirements

How do I calculate the wattage of my laptop

19v 7.89A, these are the numbers to calculate the power needs of your laptop. 19v is 19volts and 7.89A is 7.89 amps. I found these on the label of my laptop in the picture above. All you need to know is the volts and amp draw.

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Simply multiply volts times amps, V x A to get watts

For my laptop, I need 149.91 Watts. So I will look for a power inverter that is 150 watts or more. I know at some point im going to want to plug something else in at the same time as my computer and its probably going to be a small electronic device. So Im going to go ahead and size up to a 200 watt power inverter just so I dont have any issues using other devices at the same time.

Power inverters will have continuous and peak power. I size my power needs on max power and then buy the power adapter on continuous power. By doing this you give your self a little extra cushion so you are not always over doing your inverter. Inverters get hot and when your talking about small ones, they are inexpensive and I don't put a lot of faith in the cheap components they use.

I decided to buy a pure sine wave inverter.

What is the advantage of sine wave inverter?

It offers clean power with very low harmonic distortion. So what right? This actually helps motors run quieter, cooler, and faster. In most situation a sine wave inverter will run everything a conventional inverter will run even if you dont need it.

Modified Sine Wave

Except: There is also modified sine waves inverters. A modified version will not power a microwave properly.

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Inverters, How do they work ?


After Calculating my needs and researching inverters I decided to spend a few extra bucks and have a high-quality sine wave inverter. It comes with an 18month warranty and has tons of good reviews so I feel good about my buy. Your not going to believe how small these are. Check it out below.