Can a portable generator charge a Tesla?
The answer is yes but there are a number of caveats.
In this post, I will tell you everything you need to know about using a generator to charge a Tesla.
Many portable generators will not work and there are a few things you definitely need to know before using a generator in this unique situation.
At first glance, the idea of using a generator to charge a Tesla sounds ridiculous. After all, the point of owning an electric automobile like a Tesla is that you want to avoid using gas, right?
Why then would you be interested in using a gas-powered generator as a charging source?
Think about why you would use a generator in general.
A portable generator comes in handy as a backup power supply in case of power outages.
It’s also a helpful tool for situations where there isn’t a power supply handy. Both of these reasons would be just as valid for charging your Tesla.
If the power went out, you’d probably still need to get around. If you were traveling in a remote area or camping off-grid, you’d still need to get home. A generator shouldn’t be a first choice for charging your Tesla but there are definitely situations where you might want to use one.
Tesla’s official charging instructions say not to use a portable generator.
That said, it can be a safe and effective option in case of an emergency as long as you know what you’re doing.
Portable Generators as a Backup Power Supply for Charging a Tesla
Not all portable generators will work for charging a Tesla. There are a few important things to consider.
The generator absolutely must have a clean sine wave output. This means that your generator needs to be an inverter.
The Tesla charging system can tell when the output isn’t a clean, pure sine wave and it won’t let you charge.
This is important because a surge could end up causing damage.
Tesla built in a nice safety feature by not allowing a charge unless the power is stable.
In theory, all inverters will offer a pure sine wave but in reality, this isn’t always the case.
Some inverters have a modified sine wave, often a square wave or modified square wave. Your Tesla would view this as dirty or unstable energy and wouldn’t let you charge.
You only want a pure sine wave output.
Generally, the more inexpensive power inverters will have modified sine wave rather than pure.
If you want to have a better understanding of the different types of sine waves, check out this white paper from Champion.
Portable Generators with sine wave output
The other important thing to know when finding out if a particular generator will work is that the Tesla wants the generator to be grounded.
In many cases, the generator’s frame will act as a sufficient grounding element.
The Champion and Generac models are considered to be properly grounded to a Tesla.
In other cases, though, the Tesla charging system will sense that the generator doesn’t have a true ground and will not charge.
For the Honda generators, this is definitely the case. To remedy this, you’ll need a special adapter plug that bridges the ground and the neutral with a resister.
You can also just use some copper wire to connect the ground and the floating neutral.
For some generators, you’ll want to actually truly ground the generator by driving a metal rod into the earth and connecting it.
You’ll also want to use a generator that offers a fair amount of wattage, generally at least 1500W.
A small generator that offers minimal power isn’t going to get you very far.
How to Charge Your Tesla With a Portable Generator
Once you’ve determined that your generator is an inverter that offers the clean and stable energy of a pure sine wave and that it has adequate grounding, you need to know exactly how to charge your Tesla with it.
The most important thing to know is that you should always start with lowest charge rate possible, then slowly adjust up to 28-30 amps.
This will just be easier on your generator’s motor and will prevent overloading.
Teslas will by default try to draw 40A/240V, or 10,000 watts from a NEMA 14-50 outlet, so it’s important to adjust the amperage down before trying to plug in the generator.
What About Other Electric Vehicles?
Teslas are not the only electric vehicles that you can charge with a portable generator in an emergency situation.
Other EVs like the Chevy Volt and the Nissan Leaf, for example, can also be charged by a gas-powered generator in a pinch.
The same caveats regarding pure sine wave inverter energy, the possible need for grounding, and the amperage adjustments will still apply.
Other Things to Note
Charging a Tesla or other EV with a portable generator will take a long time.
Of course, when you are charging in an emergency situation, you probably don’t want or need to charge the car fully.
With a 4000W generator, it would take over 24 hours to fully charge the car.
It would also take several tanks of gas.
In most cases, you should be able to charge the car enough to at least get to a proper power supply in a few hours and on a single tank of gas rather than all day.
With the Generac iQ2000, you should be able to get 12-18 miles worth of power per gallon of gasoline, as demonstrated by KmanAuto on the video below.
Some people have wondered about whether you can rig up a portable generator to power the car while you’re on the road as a way to extend the drive capability of the car.
While this might sound like an enticing idea, it’s really not safe.
You cannot charge while driving without doing some serious (and warranty-voiding) modifications to the Tesla. That’s definitely not advisable.
It’s very important to note that a generator needs regular maintenance.
If you don’t perform this regular maintenance, the generator won’t start when you need it.
If this is the only use you foresee for the generator, keep in mind that you’ll need to attend to it regularly even though you won’t actually use it very often.
All in all, a portable generator can be a relatively cheap and reliable backup power supply that can provide some serious peace of mind.
Put the generator and some gas in the trunk and head out on a road trip or out for some off-grid camping.
Or just keep the generator and some gas on hand at home so you’re prepared for a power outage.
As long as the generator is an inverter that offers a pure sine wave and it has some kind of grounding solution, you should be able to charge your Tesla.
The Generac iQ2000 (check out my full review here) is my top recommendation for this use, as it offers a pure sine wave, has a built-in ground-neutral bridge, and is relatively affordable.