Charging My Electric Vehicle with a Portable Generator

If you drive an electric vehicle, you might dread an unexpected, extended power outage. Consistent access to electricity for battery power is a crucial component of driving an electric car.

Can you charge an electric vehicle with a generator? Yes—but, you’ll have to take some precautions, choose a generator that’s the right size, and take care while using your generator to charge your electric vehicle.

Can you draw enough electric power from a generator to charge an electric car? Once you choose the right generator for the job, how do you keep your car, your generator, and yourself safe during the charging process?

Let’s break down some important considerations for charging your electric vehicle using a portable generator.

How Much Power Do You Need to Charge an Electric Vehicle?

Generally speaking, electric car owners have three charging options for their vehicle’s electric motor, and each requires a different level of power:

Level 1 charging – Level 1 chargers use a standard, 120-volt power source—like an outlet with a dedicated circuit. These chargers require significant time for recharging.
Level 2 fast charging – Level 2 chargers are the most commonly-found charging stations in public places, but many drivers install these 240-volt power stations at home to charge their cars quickly.
Level 3 DC fast charging – Level 3 chargers use direct current (DC) for fast vehicle charging, but they’re not very practical for at-home use due to their power draw and expense.

These traditional power options provide substantially different recharging timelines. Why? Because they each offer different amounts of power. And the more power a charging station can offer, the less time it will take your car to recharge.

Since generator size is typically measured in watts, let's break down what each of the above delivers in terms of wattage. We need three crucial pieces of information for the calculation:

Voltage – The “pressure” at which electrical energy moves through an electrical system
Amperage – The “rate” at which electricity moves through a circuit
Power factor – The efficiency at which an electrical device converts volt-amps into watts, represented by a number between 0 and 1 (with 1 representing 100% efficiency)

Then, we multiply all three figures to calculate the wattage offered by a system. In the examples above, let’s assume that:

The 120-volt outlets are using 15-amp circuits
The 240-volt outlets are using a 30-amp circuit
The Level 3 chargers offer 480 volts and use 100-amp circuits
All three chargers are relatively efficient, offering a 0.98 power factor

Here’s how the wattage formulas break down in each charging option above:

Level 1 – 120V x 15A x 0.98 = 1,764 watts
Level 2 – 240V x 30A x 0.98 = 7,056 watts
Level 3 fast charging – 480V x 100A X 0.98 = 47,040 watts

These wattages put each EV charging option into perspective, especially concerning charging time. Realistically, any of the wattage outputs above will charge your car, but increased wattages offer shorter charging times.

What Size Generator Do I Need to Charge an Electric Car?

The most important point above is that the more wattage an electric power source can provide, the less time it takes to charge your electric vehicle.

So, can a generator charge electric cars? Yes.

The generator size you need depends on the battery capacity of your electric vehicle, the available time you have to charge it, and the average fuel reserves you’ll have on hand.

So, if you’re primarily purchasing a backup generator as a secondary charging station for your electric car, it probably behooves you to go big—unless you have unlimited time for charging and unlimited space for fuel.

6 Best Practices for Charging an Electric Vehicle with a Generator

So, you’ve purchased a generator to use as a backup power source for your electric vehicle. What now? Let’s break down six best practices that will keep you safe, preserve the longevity of your generator, and protect your vehicle.

#1 Consult Your Vehicle Manufacturer for Generator Charging Tips

Before you make any purchases, fuel up your generator, or connect your charging cables to your backup power source, consult with the people who understand your electric vehicle best—the manufacturer.

Quiz them about:

Any factory tests completed related to generator charging
The ideal NEMA charging cable
Tips for increased efficiency
Temperature gauges, automatic shutoffs, and other safety features to be aware of while charging with a generator

Your vehicle manufacturer will provide the best advice related to your specific make and model.

#2 Always Operate Your Generator Outdoors

Since generators emit potentially harmful gases, they should never be used indoors. You should run your generator in a space with:

Adequate ventilation
Protection from rain and standing water
Plenty of space for your generator to circulate air

#3 Don’t Overload Your Generator

Your electric car may have a feature that allows you to control the flow rate between your power source and your car. If so, you should use this feature to ensure that you’re not overloading your generator.

Overloaded generators can:

Heat up, increasing your fire and burn risk
Automatically shut off (a safety feature found in newer generator models)
Provide intermittent power, which can damage both the generator and the device or appliance that you’re operating or charging

#4 Perform Regular Test Runs

You should perform two types of tests with your generator and electric car:

Regular, short test runs to make sure your generator is in working condition.
An initial time test to see how long it takes your car to completely charge or deplete your generator’s fuel supply (whichever comes first).

The first test is a standard precaution that will help you identify potential problems before they escalate. But the second will give you a frame of reference for how long your battery will take to charge if you ever need to use your backup power source.

#5 Maintain and Service Your Generator

Throughout its life, make sure to maintain and regularly service your generator by:

Changing and flushing the oil as needed
Changing the air filter, or oil filter if applicable
Cleaning the exterior, fixtures, and space around your generator
Taking it to a generator service provider for routine checks

These efforts will help keep you safe and ensure that your generator is always ready when you need it.

#6 Monitor Your Generator’s Temperature Gauge

Especially during test runs or the first time you use your generator during an outage, keep an eye on your generator’s temperature gauge. Whether it uses a needle or a digital display, make sure that the running temperature is always within a safe range—your manual or a generator service technician can help you determine a safe temperature range for your specific machine.

If your generator begins to overheat:

Immediately power it down
Don’t touch it—the surface could be hot
Unplug anything connected to it
Let it cool down before attempting another operation cycle

If overheating persists, keep the generator off and call a service technician.

DuroMax: Off-Grid Power Access When You Need It

You can charge an electric vehicle with a generator, and generators are an excellent option for drivers looking for a backup power source for unexpected outages at home.

And, if you’re looking for a generator, you’ve come to the right place. At DuroMax, we offer the best generators on the market. Our products are equipped with state-of-the-art safety features like CO alarms and automatic shutoff. Moreover, many of our devices harness the power of tri-fueling—they can run on gasoline, propane, or natural gas.

Do you live in a place where a hurricane may be the biggest power-related threat to your home? DuroMax can help you with all of your hurricane-related questions as well, whether it be how to prepare for a hurricane , what to do during a hurricane , or if a hurricane generator fits your home’s needs.

If you’re looking for reliable power access—even when the grid fails—explore our line of backup generators.

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