Does a Power Inverter Drain Car Battery

Adding a power inverter to a truck, RV, or car opens up a whole world of possibilities in terms of electronics types that you can simply use on the roads.

Suppose that you were on your way and the battery suddenly died in the middle of your track. Sounds Super annoying, doesn’t it?

The problem of a power inverter draining a battery is highly complex. The rule of thumb is that the power inverter will not drain a battery if your vehicle is running. 

However, making use of an inverter while the engine is turned off will somehow turn the car battery down. And unfortunately, it does not take much unless the engine will not start back again without a charge or jump.

To solve all your issues, I came up with a comprehensive guide on whether a power inverter drains a car battery or not. Without any further ado, let’s have a look below for knowing all the essential factors about power inverters. So, let’s get started;

Does a Power Inverter Drain Car Battery?

You’re probably wondering if the power inverter for the car drains the car battery or not, right? Well, I have just got what you’re looking for. An inverter that is turned on uses some power. It will continue to use power from the battery in case there is no switch on your inverter.

Yes, the inverters drain the car battery, unless you have any engine working, Usually, power inverters are really inefficient, especially the ones that are cheap and of poor quality. So, it is always better to spend a little more and get the best and durable ones. 

If your inverter is switched on but not converting current because you haven’t plugged in any load, it can still draw current from the battery.

How Fast will a Power Inverter Drain a Car Battery?

Well, everyone who has an inverter obviously thinks about it. The inverters usually run at a loss means they don’t usually give 100% efficiency and range between 85 to 90%.

Drainage depends on what you are powering with the inverter. The more the consumption of power, the more a car battery will discharge speedily.

If you have inverting machines like a heater, hairdryer, or sound system, it will kill the battery in just a few hours. 

The essential point is that the batteries subside under load, which clearly means that if you remove the load, it’ll instantly bounce back.

How Long can You Run an Inverter on a Car Battery?

Now that you have an idea of what drains the car battery, let’s move on to how long you can run an inverter on a car battery.

Inverters aren’t an ideal way for providing power to different electronic things until there is no other choice because there are some losses in the system.

Suppose you want to run a light bulb of 250 watt 110VAC from an inverter for about 5 hours.

  • Watt-hours = watts * hours = 250 watts * 5 hours = 1250 watt hours
  • Account for the efficiency of the inverter, say 85%
  • Watt-hours = watts * hours / efficiency = 1250 / 0.85 = 1470 watt-hours
  • Since watts = amps * volts divide the watt hours by the battery’s voltage to calculate amp-hours of battery storage
  • Amp-hours (at 12 volts) = watt-hours / 12 volts = 1470 / 12 = 122.5 amp-hours battery required to run a 250 watt bulb for 5 hours

However, if you’re using a different load, then the amp/hours will definitely be changed by simply dividing the watt-hours by the voltage of the battery that you’re using. You can calculate Amp-hr and watt-hours from the above formulas.

The above discussion shows that the duration entirely depends upon various other factors like the power of the load and battery as well as the appliances or gadgets that are getting power from it.

How To Use a Power Inverter With a Car Battery?

For the AC appliances, the inverters usually convert about 12 volts into 110. It is pretty convenient to connect & use an inverter along with a car battery. Wanna know some easiest steps to make a perfect connection?

Here is a step by step guide;

  1. Take the 2 sides of the negative and positive plug and then plug those cables into your car battery.
  2. Always connect a DC breaker between battery and inverter to completely cut off the battery when not in use.
  3. Turn it on & check it by connecting the device with this to ensure that it’s working or not.
  4. For making the inverter stable, simply put a piece of wood under it.

Product Recommendations

Here are the most recommended and useful products in the market according to my experience that will surely benificial for you.

Best Power Inverter for Car

Ampeak product has excellent quality & features and has no irritation noise to interfere with reception and audio. It is one of the best power inverter for car.

This fantastic inverter draws a minimal amount of power, making it a marvelous device for saving a lot of electricity. In addition, the long-lasting warranty of this power-saving product is also a great plus! 

Power Inverter for Car

Cobra Pro: This Power Inverter is a real deal, I would say. The LCD screen of this product is one of its awesome features, as you can see the actual time of what output/input the inverter is pushing.

Plus, you can easily mount it by using different screws in your vehicle. Four superb ports in order to plug into power are wonderful for connecting more devices at the same time.

How Long Will a 12V Battery Last With An Inverter?

The time interval actually varies, as it entirely depends on the inverter power and size or household attached to it. But still, you can easily find out how long it will last. 

You can simply calculate either through online calculation or by using the formula. 

A 12-volt car battery with a complete charge will typically generate about 500 watts of power. For 100 watts AC load, the current of 12V DC would be about 10 Amps – so your 200 watts load will draw almost 20 Amps from your car battery. So battery lasts 2 and a half hours with an inverter for reaching the 100ah battery capacity.

And that’s the point where you should definitely stop. If you’re running the battery below 10.5 VDC twice or thrice, it is most probable that it’ll kill your battery. 

How Much Power Does An Inverter Draw With No Load?

In general, it’ll draw a very little amount of current when not in use. However, every inverter will draw a different amount. So, it is better to examine the specs on it first.

No Load Power Drain or Standby Current is an essential figure if you leave the inverter on so that it delivers full power automatically when a device is turned on. The quality inverters only draw a fraction of an ampere at idle. 


Your priority should be improving the battery life. For this purpose, don’t discharge the battery more than 50%, and you’ll get satisfying results.

Related Article: Why Does My Car Battery Drain so Fast