# What size generator do you need to run a 13500 BTU RV air conditioner?

The size of the generator that can run your RV air conditioner will depend on the maximum power usage (Wattage) of the air conditioner. The Generator you choose should have a Wattage rating that is greater than the maximum power usage of your air conditioner.

Of course, if you plan on simultaneously running other appliances on the generator as well, their power usage should also be taken into consideration.

So, to determine the size of the generator that you need to run your 13500 BTU air conditioner, you’ll first need to determine the maximum power usage of the AC unit, and then combine that with the power usage of the rest of your appliances.

In this article, I’ll discuss the power usage of 13500 BTU RV air conditioners, explain how to determine it, and then show you how to use it to calculate the size of the generator that you need.

Additionally, if you’re up for some quick estimates, you’ll also find a calculator that does all the calculations for you and estimates the size of the generator that you need.

Let’s jump in.

## How many watts does a 13500 BTU air conditioner use?

When its compressor is running, a 13500 BTU RV air conditioner will use between 1300 and 1800 Watts of power, depending on the model of the AC and its efficiency. However, this wattage range represents the “Running” Wattage of the air conditioner. A 13500 BTU air conditioner may require up to 7500 Watts of power when starting up.

Let me explain.

Air conditioners have 2 power ratings that you should consider:

• The Running Wattage of the air conditioner: This represents the amount of power that the AC uses when it’s up and running.
• The Starting/Surge Wattage of the air conditioner: This represents the amount of power that the AC requires when starting up.

The starting wattage of your RV air conditioner is a surge in power usage that only lasts for a moment, but can potentially go as high as 6 times its running wattage.

When sizing a generator for your air conditioner, you’ll need to make sure that the generator has the capacity not only to run the AC but more importantly, to be able to start the unit.

Since the power usage of an air conditioner is at its highest when the unit is starting up, the wattage capacity of the generator should be equal to or greater than the “potential” starting wattage of the air conditioner.

### So, How do you determine the starting watts of your 13500 BTU AC?

Well, you can determine both the Running and Potential Starting wattages of your air conditioner using the electrical ratings specified on its nameplate.

For example, let’s take a look at the following nameplate of a 13500 BTU RV air conditioner:

On the nameplate, we can see the following specifications:

• A/C (Alternating Current) Volts: The air conditioner operates at 115 Volts.
• Compressor LRA: LRA stands for Locked Rotor Amperage, and it represents the maximum amount of current (Amps) that the compressor might potentially require to start up.
• Compressor RLA: RLA stands for Rated (or Running) Load Amperage, and it represents the amount of current (Amps) that the compressor draws when it’s running.
• Fan Motor FLA: FLA stands for Full Load Amperage, and it represents the amount of current that the fan motor draws when operating at maximum speed.
• Optional Electric Heater Amps: This air conditioner is equipped with an optional electric heater, and this rating represents the maximum amp draw of the heating element.

Here, I explain how the “Compressor RLA”, “Fan Motor FLA”, and “Electric Heater Amps” ratings can be used to calculate the Running Wattage of these air conditioners in both cooling and heating mode.

However, as mentioned above, the size of the generator that you need will mainly depend on the Starting Wattage of the air conditioner, which can be calculated using the “Compressor LRA”, the “Fan Motor FLA”, and the Voltage of the unit:

Potential Starting Watts = (Compressor LRA (Amps) + Fan Motor FLA (Amps)) x Voltage (Volts)

If we look at the nameplate, we can see an LRA rating of 63 Amps, an FLA of 3.4 Amps, and a Voltage rating of 115 Volts:

Potential Starting Watts = (63 Amps + 3.4 Amps) x 115 Volts

Potential Starting Watts = 66.4 Amps x 115 Volts

Potential Starting Watts = 7636 Watts

Now, it is essential to understand that the initial wattage required by this air conditioner may not always reach 7636 Watts, as it typically hovers around 3000 Watts.

However, if, for any reason, the rotor inside the compressor gets “locked up”, it will necessitate the full 63 Amps to “unlock”, and the AC will require the full 7636 Watts. In such a scenario, it becomes crucial to ensure the generator is appropriately sized; otherwise, it may fail to start the air conditioner.

Before I explain what “sized appropriately” means, let’s first examine an alternative approach to limit the “Potential Starting Wattage” of your air conditioner.

### How to limit the Starting Wattage of your 13500 BTU RV air conditioner?

There are a couple of methods that can be used to limit the current (Amps) demands of an air conditioner at start-up, all of which entail installing a device. The most popular devices that are currently used for this purpose are soft starters, such as the Micro-Air EasyStart 364 and the SoftStartRV devices.

With one of these devices installed, the potential starting wattage of an air conditioner can be reduced by at least 50%, and even up to 75%. This means that the size of the generator that you’d need to start and run your air conditioner can also be reduced by up to 75%.

By employing a soft start kit, not only can you use a more affordable and portable generator, but you can also extend the lifespan of your air conditioner while decreasing the fuel consumption of the generator. To learn more about this, check out our detailed guide here.

To get a better understanding of how these devices are installed, watch the following instructional video:

Now, let’s see how you can use the starting wattage of your 13.5k BTU air conditioner and the running wattage of your other appliances to calculate the size of the generator that you need, and let’s also see how big of a difference these soft starter devices make.

## What size generator do you need to run a 13,500 BTU RV air conditioner?

Similar to air conditioners, generators also come with two Wattage ratings:

1. Running (or Rated) Wattage rating: This indicates the amount of power (Watts) the generator can continuously produce under normal operating conditions.
2. Peak/Maximum Wattage rating: This represents the maximum amount of power the generator is designed to produce briefly when there is a surge in demand.

Usually, the Peak (Maximum) Wattage of a generator is around 110% to 130% of its Running (Rated) Wattage. This additional capacity allows the generator to handle short-term spikes in power demand, ensuring it can manage sudden surges or startup loads from various appliances without getting overloaded.

To reliably start and run a 13500 BTU RV air conditioner, the generator’s Peak Wattage rating should be greater than the “Potential” Starting Wattage of the AC unit, which can be determined using the compressor’s LRA (Locked Rotor Amps) and the Fan Motor’s FLA (Full Load Amperage) ratings:

Potential Starting Watts = (Compressor LRA (Amps) + Fan Motor FLA (Amps)) x Voltage (Volts)

In general, the Potential Starting Wattage for these RV air conditioners ranges from 6000 to 8000 Watts, or 2000 to 3000 Watts if the air conditioner is equipped with a soft starter.

If the air conditioner has a soft starter, you’ll need a generator with a Peak Wattage rating of 2000 to 3000 Watts, such as the Honda EU2200I or the

For air conditioners without a soft starter, a generator with a Peak Wattage rating of 6000 to 8000 Watts, such as the Westinghouse 6600W or the DuroMax XP8500EH, would be necessary to ensure reliable operation.

However, a better solution in this case would be to use 2 generators such as the Westinghouse iGen4500DFc wired in parallel using the Westinghouse 507PC 50A Parallel Cord.

Of course, this is assuming that no other appliances will be operating on the generator during the air conditioner’s startup.

If other appliances will also be drawing power simultaneously with the air conditioner, the running wattage of each appliance should be added to the air conditioner’s Starting Watts when sizing the generator:

Generator’s Peak Wattage > Air Conditioner’s Starting Watts + Running Watts of other Appliances

Now, to understand this, and to make the case for soft starters, let’s look at a couple of examples.

### Example 1:

Let’s consider an example where we need to size a generator to power the following loads:

• A 13500 BTU RV air conditioner that has a compressor LRA rating of 54 Amps and a Fan Motor FLA of 2.8 Amps.
• An RV fridge that uses around 200 Watts of power.
• A TV that uses 50 Watts.
• A few lights that use around 100 watts

First, we calculate the potential starting watts of the air conditioner:

Potential Starting Watts = (Compressor LRA (Amps) + Fan Motor FLA (Amps)) x Voltage (Volts)

Potential Starting Watts = (54 Amps + 2.8 Amps) x Voltage (Volts)

Potential Starting Watts = 56.8 Amps x 115 Volts

Potential Starting Watts = 6532 Watts

Now, assuming all of our other appliances are turned on when the air conditioner starts, except for the refrigerator, which should be turned on separately, we calculate the Peak Wattage of the generator as follows:

Generator’s Peak Wattage > Air Conditioner’s Starting Watts + Running Watts of other Appliances

Generator’s Peak Wattage > Air Conditioner’s Starting Watts + Refrigerator’s Running Watts + TV’s Running Watts + Lights’ Running Watts

Generator’s Peak Wattage > 6532 Watts + 200 Watts + 50 Watts + 100 Watts

Generator’s Peak Wattage > 6882 Watts

In this case, a generator with a Peak Wattage rating greater than 6882 Watts would be suitable. For example, the Westinghouse 7500-watt generator, with a Peak Wattage of 7500 Watts and a Running Wattage of 6000 Watts, would be a good fit for powering these loads simultaneously.

However, for a more portable option, 2 Westinghouse iGen4500DFc generators can be wired in parallel using the Westinghouse 507PC 50A Parallel Cord, which would provide up to 9000 Starting Watts and 6000 Running Watts.

Example 2:

In this example, let’s consider that our 13500 BTU air conditioner is now equipped with a Micro-Air EasyStart 364, which conservatively limits the starting wattage of the AC to 3000 Watts.

The required Peak Wattage of the generator is calculated as follows:

Generator’s Peak Wattage > Air Conditioner’s Starting Watts + Running Watts of other Appliances

Generator’s Peak Wattage > Air Conditioner’s Starting Watts + Refrigerator’s Running Watts + TV’s Running Watts + Lights’ Running Watts

Generator’s Peak Wattage > 3000 Watts + 200 Watts + 50 Watts + 100 Watts

Generator’s Peak Wattage > 3350 Watts

With this upgrade, a smaller generator such as the DuroMax XP4000S would be a great fit, as it can handle up to 4000 Starting Watts and 3300 Running Watts.

To make things easier for you, I’ve created a calculator that allows you to list all your appliances, estimate their running and starting wattages, and then calculates the size of the generator you would need to power your air conditioner and other appliances reliably:

Generator Size Calculator
Appliance:
Running Wattage (Watts):
Max. Wattage (Watts):
Required Generator Size (Peak Wattage) in Watts:
0 Watts (W)
Required Generator Size (Peak Wattage) in kiloWatts:
0 kiloWatts (kW)