Can a Portable Generator Charge a Tesla? What You Need to Know

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. 

Honda gasoline generator charging a tesla electric car

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

tesla monitor showing the charging screen

Some examples of inverter generators that do have a pure sine wave output are the Champion 9200W/11500W, the Generac iQ2000, and Honda’s EU2200i and EU7000iAT1 models.

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.

11 thoughts on “Can a Portable Generator Charge a Tesla? What You Need to Know”

  1. This is very interesting. Would the same caveats and techniques work for charging a Powerwall? I have been told by Tesla that the Powerwall won’t charge from a generator because the signal (sine wave?) won’t be recognized. However, the Tesla rep said that their design team might be able to come up with a work- around for this. I live in Puerto Rico, where the grid is very unstable. Usually, I can charge my Powerwall with my solar array, but in a situation with the grid out and bad weather for a day or two, I could be left without power. So, I Very much want to be able to charge my Powerwall with my Honda inverter generator.

    I would love to hear from anyone who has insight on this.

    Reply
    • Pendiente a esto tambien! Vivo en PR y me pasa lo mismo con el powerwall, quisiera saber si con una plantita inverter puedo cargarlo!

      Reply
    • Nevin, what voltage is your solar array outputing, you can get some very large switched mode power supplies for use in computer servers, it’s fairly easy to get them in the 4400 watt range for ~$150 USD and most will output 48 VDC and they honestly don’t care what they are getting for input power so long as it’s between 200 to 300 volts AC and basicially between DC to 1000 Hz, I know people think large computer servers would be fussy, in reality they can work with very “dirty” power with ease, and then you could use them to feed DC into your solar controller / inverter between the panels and the powerwall, and the nice thing is you can use two or three in parallel to double the current, and if you need a higher voltage you can conect them in series to double the voltage ( but you do need to modify them to do this they are made for parallel useage for redundancy with a server so it doesn’t go down if a power supply fails, but to run them in series you need to isolate the negative output from the case ground, normally this is a few plastic washers and plastic screws ) but if you use two of them you can charge your power wall in under an hour, well assuming your generator outputs at least 10 kW, and most server power supplies are 90 to 98 % efficient so they don’t waste much power.

      You can also get them in a lower voltage most 12 volt units are 1000 to 2200 watts, same input voltage range but the 4000watt plus are normally 48 volts but there is nothing stopping you from using 10 12 volt units to get 120 VDC at 10 kW and since they are about $20 to $30 each it’s under $300. All prices are for used ebay type units like a HP DPS800gb, new units are about 10 times the used price and using them for projects like this will invalidate there warrenty so in my view it’s not worth going with new but it’s upto you. Keep in mind this type of project is not recommended unless you have good working knowledge and are aware of the risks of working with electricity and high current DC power, and having access to a 3-D printer to make a nice case would be ideal if you want it to look nice and be safe for smaller fingers.

      If your honda is a 120 only version you will need to use the smaller 1 to 2kW supplies as they will run on 100 volts to about 300 volt range with a small reduction in wattage at 120 most 1000 supplies will do about 850 watts on 120.

      Tesla should allow DC direct charging, of there powerwall, more solar users might look at them if they did, why do we want to waste power converting DC to AC only to have the powerwall convert it back to DC for battery, it’s a waste of power.

      Reply
  2. Fantastic. Have been looking for this information for months. The Hyundai Ioniq electric I intend to buy is a little short of the distance I need for a round trip and charging stations are not always convenient in Australia. (They are in parking stations but you have to pay for the parking and you cannot ensure that some other idiot has not taken your EV charging spot). The generator I have in mind is said to be such pure sinewave that phones and computers can be used on it. As to the earthing requirements of the Ioniq I have not heard yet from the Australian agents. Has anyone tried an Ioniq on a petrol generator?

    Reply
  3. The non inverter generators that run at constant speed also produce pure sine waves. These generators work the same way as the ones in the power company but the frequency of 60 Hz (US) may be higher or lower but shouldn’t be a problem for the internal charger in the car.
    There was an engineer near Berkley CA that interfaced a Capstone micro turbine generator to a LEAF using the CHADMOE interface to charge at 50KW.

    Reply
    • Keith while they are like large generators used at power stations, they use diffrent controls, a small genset will have a very simple capacitor type automatic voltage regulator (AVR) power companies use very accurate controls and spinning reserves, and since small generators have a much smaller mass, they can have large fluctuations in frequency as the load is changed, most power companies are have several hundred tons of mass, something like a Siemans 1300 MVA SGen5-3000W is 425 tons and it’s synchronised to an atomic clock thanks to GPS so you really do get 60 Hz measured over a day, and there is also no large magnetics like transformers which are found on the grid to smooth the sinewave, so you can get some pretty ugly harmonics and noise on the power from a generator, but i’m not saying this can’t be fixed, if your willing to lose a few percent ( 10 to 20% )of the system efficiency you can add a simple ferroresonant transformer to the system and you will end up normally with better then grid quality power, why don’t portable generator manufactures do this well, they are expensive new, they more then likely weigh more then the portable generator powering them and they will reduce the run time of the generator, but thats not saying you can’t add one, but from a marketing point of view it’s not good for sales.

      Most cars will have a problem with noise / harmomnics on the line as they are simple to detect and while short term noise / harmonics might not be an issue, the car manufacture has warrenty obligations to consider and in the long term harmonics / noise will add heat to the system and can cause undesired operation, and can cause components to fail, so it’s simpler for them to just not allow charging under less then ideal conditions, could you image the PR nightmare of a Tesla catching fire when charged by a honda generator, both honda and tesla don’t want to be thrown under that bus. So out of abundant safety they just don’t allow chargeing, but if your willing to DIY you more then likely can.

      Reply

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