# What size generator to run your RV AC? A detailed guide

Generators are classified based on their Electrical Power Capacity, which is typically measured in Watts (W) or kiloWatts (kW), with 1 kiloWatt being equivalent to 1000 Watts.

To power your RV air conditioner effectively, your generator’s Wattage capacity should exceed the power (in watts) required by the AC unit, with some additional capacity to run your other appliances comfortably.

In this article, we’ll start by discussing the power consumption (Watts) of RV air conditioners. I’ll provide estimates, explain the correct approach for determining the maximum power usage of your RV AC, and even offer tips on how to reduce it, which will allow you to use a smaller generator.

Once we have a solid understanding of RV AC power requirements, we’ll move on to calculating the appropriate generator size needed to support your RV’s AC unit and other appliances during your boondocking adventures.

I’ll walk you through the proper manual calculations for this, and I’ll also offer a handy calculator for added convenience.

Finally, I’ll discuss the fuel consumption and efficiency of RV generators.

Let’s dive right in.

## How many Watts does an RV AC use?

Common RV air conditioners typically come in 13500 or 15000 BTU ratings, and as a general rule of thumb, AC units in this capacity range may need approximately 1800 to 2000 Watts of power during regular operation. For RV ACs with lower cooling capacities, usually ranging from 5000 to 10000 BTUs, their power consumption can fall between 500 and 1200 Watts.

However, it’s important to note that these power figures represent the AC units’ “running” power usage. During startup, an RV air conditioner might momentarily demand up to 8000 Watts of power.

Before diving into the specifics, to provide you with a quick reference, here’s a table categorizing RV ACs by their BTU ratings and offering estimations for their maximum power requirements (Watts) during normal operation and startup:

Please note that the values presented in the table were determined based on the standard electrical specifications of these RV air conditioners.

While these figures provide an estimate, they may not precisely reflect the typical power consumption of these RV AC units. However, they do represent the upper limit of power these ACs might potentially demand during normal operation and startup.

When choosing an appropriate generator to ensure your RV AC operates smoothly, it’s crucial to select a generator with the capacity to match the maximum potential power requirement of your AC unit, especially its “potential” starting wattage.

Let me elaborate.

our RV air conditioner primarily consists of two key components that consume power:

1- The compressor:

This component serves as the core of the air conditioner, responsible for compressing and circulating the refrigerant within the coils to facilitate heat exchange.

The compressor has two electrical ratings that specify the maximum electricity it might require during operation and startup:

• An RLA (Rated Load Amps) rating: This rating denotes the maximum current (in Amps) that the compressor may draw during standard operation.
• An LRA (Locked Rotor Amps) rating: LRA represents the maximum current (in Amps) the compressor could demand to overcome its stationary state and gain momentum.

The compressor is the primary power consumer in your RV air conditioner, particularly during startup.

2- The fan motor:

The fan motor is responsible for driving both the condenser and blower fans. These fans respectively expel heat outside and distribute cool air within the ducting.

The fan motor is equipped with an FLA (Full Load Amps) rating, indicating the maximum current (in Amps) it may require during regular operation.

When you turn on your RV’s AC, the fan motor typically activates first, followed by the compressor after a few seconds. Consequently, the maximum current your RV’s AC could potentially require is the sum of the running amps of the fan motor and the starting amps of the compressor:

Potential Starting Amps = Compressor LRA (Amps) x Fan Motor FLA (Amps)

Now, power (measured in Watts) can be calculated by multiplying the current (in Amperes) by the voltage (in Volts):

Watts = Amps x Volts

In the United States, RVs and their air conditioners typically operate on a standard Voltage of 115 Volts. Therefore, the “Potential” Starting Watts of the RV AC can be determined as follows:

Potential Starting Watts = Potential Starting Amps x 115 Volts

Let’s illustrate this with an example by examining the nameplate of a 15000 BTU RV AC and highlighting the relevant specifications:

On the nameplate, the manufacturer specifies the following:

• A Voltage of 115 Volts
• A compressor LRA of 60 Amps
• A fan motor FLA of 2.8 Amps

Using these specifications, the maximum amount of current (Amps) that this RV AC may require is:

Potential Starting Amps = Compressor LRA (Amps) x Fan Motor FLA (Amps)

Potential Starting Amps = 60 Amps x 2.8 Amps

Potential Starting Amps = 62.8 Amps

Now, we can determine the maximum power (in Watts) that the AC unit may demand:

Potential Starting Watts = Potential Starting Amps x 115 Volts

Potential Starting Watts = 62.8 Amps x 115 Volts

Potential Starting Watts = 7222 Watts

It’s essential to note that this calculated value represents a worst-case scenario, as the actual amp draw of the compressor and the fan motor won’t typically reach their rated values (LRA and FLA).

The typical starting wattage for this RV AC unit usually falls within the range of 3000 to 4500 Watts.

However, according to its electrical specifications, this AC unit may potentially require up to 7222 Watts of power when it’s starting up. To ensure that the generator can reliably start and operate the AC, it must be sized accordingly.

2500 - 4000 Watt Generators

Does this mean you need a 7000+ watt generator to run your RV AC?

Well, this approach is one way to guarantee the generator’s ability to start and operate the RV AC.

But instead of going for a single, large 7000+ watt generator, which tends to be open frame, noisy, and heavy (weighing between 150 to 200 lbs), a better approach is to use two generators in parallel.

For example, you can opt for two Westinghouse iGen4500DFc and link them in parallel using the Westinghouse 507PC 50A Parallel Cord. This setup can handle up to 9000 Starting Watts and 6000 Running Watts while providing the flexibility of two smaller and more manageable generators.

An even better and more effective approach would be to limit the starting wattage of your RV AC, which would allow you to use a smaller and more portable generator, while still guaranteeing its ability to start and run your RV AC.

You can achieve this by installing a soft start kit on your RV AC.

See, a soft-starter kit such as the MICRO-AIR Easystart 364 or the SoftStartRV can be added to your air conditioner, significantly reducing its potential starting wattage by 60% to 75%.

To provide a clearer picture, here’s a table comparing the starting watts of RV ACs without a soft starter to their starting watts with a soft starter installed:

Reducing the starting wattage of your RV AC opens up the possibility of using a smaller, more portable, and quieter generator like the WEN 56380i generator.

Here’s a video that explains this in more detail, and showcases the process of installing a MICRO-AIR Easystart 364 on an RV AC:

Now that you have a better understanding of the power requirements of your RV AC, let’s see how you can use that, along with the power requirements of your other appliances to determine the appropriate generator size.

2500 - 4000 Watt Generators

## What size generator to run your RV AC and other appliances?

Generators come with two Wattage specifications that indicate their power capacity:

• A Rated (Running) Wattage Capacity: This rating indicates the maximum amount of power that the generator can continuously and comfortably supply.
• A Peak (Surge/Max.) Wattage Capacity: This is the maximum power the generator can briefly supply if needed, typically 110% to 130% of its Running Wattage capacity.

When dealing with appliances that require a relatively high amount of power during startup, such as air conditioners/heat pumps, refrigerators/freezers, washing machines, pumps, etc., the Peak Wattage rating of the generator should be the main specification to consider.

To select the right generator, you’ll need to ensure that the Peak Wattage capacity of the generator matches the surge in power usage that these appliances cause.

In this case, the Peak Wattage rating of the generator must be greater than the starting wattage of your RV AC.

To give you a general guideline, and to emphasize the benefit of installing a soft starter kit on your AC, here’s a table that estimates the generator Peak Wattage that would be required for RV air conditioners based on their cooling capacity (BTUs), and whether or not they’re fitted with a soft start:

For example, if you have a 15000 BTU AC on your RV, you would typically need a generator, or paralleled generators with a combined Peak Wattage rating of 7000 Watts or more to guarantee the operation of the AC.

However, if the RV AC is fitted with a soft starter, a single generator with a Peak Wattage rating of around 2700 Watts would be enough.

It’s essential to note that the figures in the table don’t account for the power requirements of other appliances running simultaneously on the generator.

The correct way to calculate the size of the generator is to add the highest starting watts that one of your appliances may require, to the running watts of the rest of the appliances that you plan to run together.

Soft starter or not, your RV AC is likely to have the highest starting watts. So, this rule can be expressed as follows:

Generator’s Peak Wattage > RV AC’s Starting Watts + Combined Running Watts of the rest of the appliances

For example, let’s say the generator needs to be able to run the following appliances simultaneously:

• A 15000 BTU RV air conditioner that may require up to 7000 Watts during startup.
• A couple of laptop chargers that use 150 Watts.
• A TV that uses 80 Watts.
• A few lights that require 100 Watts.
• A refrigerator that uses 250 Watts.

The required Peak Wattage of the generator can be determined as follows:

Generator’s Peak Wattage > RV AC’s Starting Watts + Combined Running Watts of the rest of the appliances

Generator’s Peak Wattage > RV AC’s Starting Watts + Laptop chargers’ Watts + TV Watts + Lights’ Watts + Refrigerator’s Watts

Generator’s Peak Wattage > 7000 Watts + 150 Watts + 80 Watts + 100 Watts + 250 Watts

Generator’s Peak Wattage > 7580 Watts

For these power requirements, we’d need a generator that has a Peak Wattage rating of 7580 Watts or more.

A cost-effective option for this would be the DuroMax XP8500EH, which has a Peak Wattage of 8500 Watts and a Running Wattage of 7000 Watts when running on gasoline, or a Peak Wattage of 8075 Watts and a Running Wattage of 6650 Watts when running on propane.

6000 - 8000 Watt Generators

A more flexible option would be 2 Westinghouse iGen4500DFc generators wired in parallel using the Westinghouse 507PC 50A Parallel Cord, which would provide a Peak Wattage of up to 9000 Watts, and a Running Wattage of up to 6000 Watts.

Now, let’s consider a scenario where a MICRO-AIR Easystart 364 has been installed on our 15k BTU RV AC, and let’s conservatively assume that the starting wattage of the AC is now limited to 3000 Watts.

Let’s recalculate the Peak Wattage required for the generator:

Generator’s Peak Wattage > RV AC’s Starting Watts + Combined Running Watts of the rest of the appliances

Generator’s Peak Wattage > RV AC’s Starting Watts + Laptop chargers’ Watts + TV Watts + Lights’ Watts + Refrigerator’s Watts

Generator’s Peak Wattage > 3000 Watts + 150 Watts + 80 Watts + 100 Watts + 250 Watts

Generator’s Peak Wattage > 3580 Watts

With this upgrade, we would now be able to use a single more portable generator, such as the WEN 56380i, which has a Peak Wattage of 3800 Watts and a Running Wattage of 3400 Watts.

Now, for your convenience, I’ve created a generator size calculator that allows you to list your appliances, provides power usage estimates, and calculates the generator size required based on those estimates:

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)

## What size generator for an RV with 2 AC units?

If you turn on one of the RV air conditioners while the other is running, the total power usage of the two ACs could potentially surge up to 9,000 – 10,000 Watts. Although this spike in power usage only lasts for a moment, the generator should be sized accordingly.

Therefore, to run 2 RV air conditioners at the same time on a generator, you’d have to use a single generator that has a Peak Wattage rating of 9,000 – 10,000 Watts such as the DuroMax XP10000EH, or 2 generators wired in parallel such as the Westinghouse iGen4500DFc generators.

However, if your RV air conditioners are both fitted with a soft starter, a generator with a Peak Wattage rating of 4000 to 4500 Watts would be enough to operate both ACs at the same time.

6000 - 8000 Watt Generators

Keep in mind that these calculations are based solely on the power requirements of your RV air conditioners.

If you have other power-hungry appliances in your RV, such as a water heater, running those appliances on gas can help reduce the electrical load on the generator.

If you plan on running some other appliances on electric, as explained in the previous section, their power usage should also be taken into consideration when calculating generator size.

This can be done through the following formula:

Generator’s Peak Wattage > Highest RV AC Starting Watts + Running Watts of the other AC + Combined Running Watts of the rest of the appliances

## RV generator fuel consumption:

An RV generator’s fuel consumption will naturally depend on its wattage capacity, the bigger the generator, the more fuel it’ll consume.

For example, a 6000-watt generator producing 5000 Watts of power will consume between 1 and 1.2 gallons of gas or between 1.2 and 1.4 gallons of propane per hour of runtime.

On the other hand, a 3000-watt generator producing 3000 Watts of power will consume between 0.5 and 0.6 gallons of gas or between 0.6 and 0.7 gallons of propane per hour of runtime.

However, the fuel consumption of the generator will also depend on how much of its capacity is actually in use.

The closer the generator is being maxed out, the more fuel-efficient it becomes. In other words, a generator operating at 100% of its capacity will consume the least amount of fuel per unit of energy it produces.

For example, while a 5000-watt generator producing 2500 Watts of power may consume up to 0.65 gallons of gas or up to 0.75 gallons of propane per hour, a 2500-watt generator producing the same amount of power will only consume around 0.4 of gas or 0.5 of propane per hour.

To visualize this, here’s a table that categorizes generators by their Wattage and estimates the amount of fuel that they’ll consume based on the % of their capacity that is in use and the type of fuel they’re running on:

To determine the amount of propane in pounds instead of gallons, simply multiply by 4.2:

Propane (lbs) = 4.2 x Propane (Gallons)