Using a Car Power Inverter As a Generator

power outage
Think twice before attempting to run an indoor heater, tv, or video game system off your car's inverter during a power outage. Craig Veltri / E+ / Getty

The short answer is that you can run electronics inside your house off a car power inverter, but it probably isn’t a good idea. If the engine isn’t running at the time, you’ll find that the car battery will die pretty fast. And if the engine is running, you’ll find that using your car as a makeshift generator is typically going to be less efficient, and less effective, than just buying a real generator.

If you have another heat source, like a wood burning stove, you’re better off using that until the power comes back on. And if the situation is really dire enough that you have to use your car inverter to run heaters in your home, you’re probably going to be better off using that gas to get yourself to an emergency shelter or warming station.

Running Home Electronics With a Car Power Inverter

Car power inverters are great, but they’re really designed to be used when the engine is running. When the engine isn’t running, the inverter draws stored power from the battery rather than relying on the power generation of the alternator. Since car batteries have a finite amount of power storage, using an inverter when the engine is off can drain a battery pretty fast. In fact, a typical car battery will have less than two hours of reserve capacity, which is defined as the amount of time that the battery can power a 20A load before the voltage drops below 10.5V.

Letting the charge drop that low, or lower, isn't very good for the longevity of a battery, which is why it's so bad to let batteries die.​

If you plug an extension cord into the inverter in your car and use it to run electronics in your house with the engine off, you may find that you can’t start your car up at all later on.

This is the reason that recreational vehicles and other automobiles that have to deliver a lot of power when the engine isn’t running typically have one or more deep cycle batteries devoted to that purpose.

What if the Engine is Running?

If you leave the engine running, and you have an appropriate outdoor extension cord handy, then it’s perfectly safe to run electronics in your home with a car power inverter. However, there are a handful of potential issues to consider. First of all, you’ll have to make sure that your inverter can provide enough power for the devices you want to run. If you bought an inverter to provide power for a DVD player, game system, or another small electronic device, it may not be able to handle the power needs of a space heater, or whatever other electronics you want to plug into it.

The other issue that you need to consider is gasoline. If you leave your car running unattended, you’ll have to check it regularly to make sure that you don’t run it out of gas. This is especially important if you’re dealing with a winter storm, since you may need that gas to get your family to a hotel, a shelter, or a warming station if the power isn’t restored in a timely fashion.

This is less of an issue if you have extra fuel stored in safe containers, and that’s something you may want to consider ahead of time.

Of course, it’s typically going to be more efficient to run a generator than to use your car engine and an inverter to serve essentially the same purpose. A large generator can even power appliances like your fridge and freezer, multiple space heaters, and even an air conditioning unit if your power goes out during the summer. The same isn’t true for most car power inverters.

If you're only going to use the inverter for heating, and you're going to buy gas especially to keep your car running, then you may want to consider alternate heating sources.

Although it isn't safe to use a portable propane heater in a car, these same units are safe to use inside your house if you're careful about ventilation.

In case you do choose to run your car in order to use your inverter a makeshift generator during a power outage, keep in mind that the exhaust fumes can be hazardous. It's never a good idea to run a car inside a closed garage due to the potential buildup of carbon monoxide and subsequent danger of carbon monoxide poisoning, and while you should be safe if your car is parked outside, you should still take the same precautions that you would with a generator, like making sure that the exhaust fumes are directed away from your house. This is even more important during a summer power outage when your windows or doors are more likely to be open.