Do Power Inverters Drain your Car’s Battery?

Power inverters are a great addition to add to your vehicle. It could be your car, truck, RV, or even your boat. These simple devices allow you to power nearly any kind of electronic or appliances straight from the comfort of your vehicle. Perhaps you are going on a long road trip with the family and you’d like to setup a television for the kids. Or, perhaps you are going on an off-grid camping trip and you’d like some warm coffee in the morning. A power inverter can solve all of these problems and more.

While setting up a power inverter is relatively easy there are still a lot of questions that surround these tools. Over the past few weeks we here at have taken the time to answer most, if not all, of these questions. Today’s topic is how power inverters and your vehicle’s batteries work together. Let’s dive in and take a look.

Power Inverter & Batteries

To understand power inverters we first need to understand the main types of electricity. There are two different types of electricity. The first is known as alternating current, or AC. This AC is what is used in all of our homes and is what all of our standard appliances and electronics plug into. The second type of electricity is known as direct current or DC. DC is what is found in vehicles such as cars, trucks, motorhomes, and even boats. This power is driven from the alternator in your vehicle and then storing that power in your standard twelve volt battery. The power inverter works to convert that DC energy over to AC energy so that you can use appliances and electronics in your vehicle.

To answer the question of this article, yes, running a power inverter will drain your battery. But, there is more to it then that. First, do you plan to run this power inverter while your vehicle’s engine is running or do you plan to run it while the engine is off? This is a BIG difference as far as battery life. If you plan to run this inverter while you are driving down the road then the chance of draining your battery goes way down. This is because that while you are driving the vehicle’s alternator is running. The alternator is what produces electric current in your vehicle. This current is then used as needed and the rest is sent to charge your battery. If you are using the inverter while driving then the alternator is continuing to provide you with power so that the battery does not drain. In theory you could run in the inverter as long as your vehicle is running.

That being said, there exceptions when using a power inverter while the engine is running. If you purchase a very large inverter, say two-thousand watts or higher, then you could end up exceeding the amps of your alternator. In other words, you are asking for so much power that exceeds what your alternator can produce. When this happens the alternator will try to keep up but what will end up happening is your battery will begin to drain WHILE you are driving down the road. If left unchecked this will eventually cause your entire vehicle to shut down as you are driving. Once you pull over to the side of the road you will be left with a dead battery.

This is why it is important to consider purchasing an aftermarket high amperage alternator. These high amperage alternators can produce much higher amounts of direct current energy then your standard OEM alternators. By installing one of these you can ensure that you will be able to run whatever you need on your inverter without the alternator being overloaded. If you are not familiar with installing one of these then I suggest visiting your local repair shop.

The other side of the coin here is running your power inverter while the vehicle’s engine is turned off. When you are doing this you are solely relying on the power stored in the vehicle’s battery. The alternator is NOT running in this scenario so it is only the battery that can provide you with power. I will tell you right now that standard twelve volt automotive batteries are NOT meant to power things long term. They are instead meant to give you the initial power to crank the engine and get your vehicle going. If these batteries fall below ninety percent capacity then you could end up permanently damaging the battery. This is why if you do choose to run a power inverter off of just your vehicle’s standard battery you can only really do so for an hour or two. Anymore and you risk having a dead battery.

There is another option here folks. If you do plan to run power inverters for a substantial amount of time while your vehicle is off then it is recommended to install what is known as an alternative battery. This is a second battery installed in your car so that when the vehicle is on it not only charges your main battery but it also charges your secondary battery. If you go this route be sure to purchase a deep cycle battery as your secondary. Deep cycle batteries are what’s used in motorhomes and recreational vehicles. They are meant to last a long time and provide a long charge. While the twelve volt battery cannot fall below ninety percent capacity a deep cycle can go as low as fifty percent. That is a BIG difference and gives you many hours, sometimes days, of power to work with.

If you do end up going with the deep cycle battery then I would also look into purchasing a higher amperage alternator as well. It may not be one-hundred percent needed but it will give you a faster charge and also ensure that you have enough power to charge both batteries.

The last thing to mention here is that once you are done with your power inverter and you are leaving your vehicle be sure to turn it to the off position. If the power inverter is left on then you could still end up draining power from your batteries. This is true even if there are no plug-ins connected on the AC side of the power inverter. The inverter can still draw five to ten percent of it’s rated wattage. It is always safest to just turn it off when done so that you do not come back to a dead battery.


In conclusion folks, yes power inverters will drain your vehicle’s batteries. The power has to come from somewhere and when it is being used it will pull from your batteries. If you are using the inverter while your vehicle is running then the alternator will recharge your battery. This will in effect give you endless power as long as your vehicle is running. On the other hand, if you are running your inverter with your vehicle’s engine off then watch it carefully and time the use. Eventually your battery will be drained to the point of no return.

I hope this article was helpful and thanks for reading.

Alec Johnson

You may also like