Solar Power for RV Air Conditioner – How to Size RV Solar Power

Solitude? Check. Idyllic landscape? Check. But does your RV have enough solar power to run an air conditioner? Maybe not! The lack of a comfortable temperature inside your rig can ruin an otherwise perfect road trip.

While powering an air conditioner with solar energy is possible, the setup calls for many solar panels and a massive battery bank.

This blog post explains how to size solar power for an RV air conditioner and whether it’s worth investing in. You’ll also learn various RV powering options and alternative ways to cool your vehicle’s interior on the road.

So, without any further ado, let’s dive in.

How Much Solar Power Does an RV Air Conditioner Need?

The amount of solar energy you need to power an RV air conditioning unit depends on the BTU rating of the unit. BTU is an acronym for British Thermal Unit and refers to the cooling capacity of the RV air conditioning units. It’s a measure of the amount of heat that an AC can remove from an RV.

As a rule of thumb, an RV AC needs around 20 BTUs for each square foot of the RV space. But other factors like the RV height, window size, and parking location might call for additional cooling power. Most RVs, however, come standard with ratings between 11,000 to 15,000 BTUs.

Most air conditioning units with 15,000 BTU of cooling capacity require around 3,500 watts of solar power to start up and about 1,500 watts to keep running. Electric motors require more power to start than the power consumed during running. Thus, the solar system you are using for air conditioning should’ve more watts than the start watts needed by the AC.

Looking at the BTU rating of your AC, you can use the number to size your RV solar power system effectively.

Sizing Your Solar Setup for RV Air Conditioning

You must consider the AC BTU rating and the time you’ll want to run your air conditioner to size your solar system properly. The essential components to consider include:

Number of Solar Panels

The RV air conditioner and the solar array require contrasting environments to give optimal results. While the RV will most likely remain cool in the shade, the solar panels need direct sun exposure to produce electricity.

For a 13,500 BTU air conditioner that requires 2700 running watts, we recommend upwards of 3,000 watts of solar panels for smooth operation. If you’ve ample roof space on your RV, you could consider 16 x 200-watt monocrystalline RV solar panels to run the 13,500 BTU air conditioner. RV solar panels with larger wattage output should do the trick if you’re limited on space.

Size of Battery Bank

In addition to proper RV solar panel setup, you’ll also need the right battery bank size to run solar-powered AC at night or on cloudy days. Regarding RV battery banks, we usually recommend lithium batteries over lead acid since they are easy to maintain and can be used to their full potential. Lithium batteries are more expensive, but the longer lifespan and the deeper depth of discharge make up for the higher cost.

Knowing your daily amperage requirement is crucial before sizing your battery capacity. If your electrical panel has an LED monitor, you could turn on the AC and read the amps rating on the screen. Once you know the amps your AC pulls per hour, you can utilize this figure to determine the required battery capacity and start wiring solar panels to RV batteries.

Example

If your RV AC unit pulls 150 amps per hour and runs it 4 hours daily, you will draw 600 amp hours (150 amps x 4 hours) from your solar battery bank. This is the minimum solar energy you need to power an RV air conditioning unit for four hours daily.

If your panels receive 6 hours of direct sunlight daily, they should generate at least 100 amps for each of those 6 hours to recharge the batteries. You can also use this number to determine your solar panels’ output wattage. Multiply the panels’ rated terminal voltage (usually 14.4v) with the total amps, and you’ll get the total wattage required for running the air conditioner.

The calculation assumes you get six hours of full sunlight and don’t run appliances other than the RV air conditioner.

Choosing the Right Solar Power Inverter

A solar power inverter is the last piece of the puzzle in your RV air conditioning setup. It’s used to convert the DC power produced by the solar panel to AC power required to run an RV air conditioner.

There are various sizes and types of solar inverters, but if you want to run an RV AC with solar panels, you’ll need an inverter with a wattage higher than the starting wattage of the AC. This means if your AC’s starting wattage is 3,000 watts, you’d require an inverter capable of outputting around 4,000 watts so you don’t max out your inverter. We always recommend leaving as much room as possible for running other AC-powered appliances.

Since the running wattage of an AC is lower than the starting wattage, you could also consider using a Soft Starter with a smaller inverter to supply power to your AC (more on it in the next section).

Soft Start System

If you want to reduce the initial power requirements of the RV air conditioning unit, you can add an extra device called a ‘soft starter’ to the setup. A soft starter limits the initial inrush of current needed to start the AC. It does so by supplying a gentle ramp, resulting in a safer and smoother start-up.

Soft starter protects the AC motor against potential damage by minimizing the heating caused by frequent start-stops. It also lowers the cost of the solar power supply system by reducing the number of solar panels needed to generate the starting wattage.

Other Powering Options for Your RV

Although solar power has been everyone’s favorite since the last decade, it may not be an ideal choice for every RVer. Here are some more ways to power your RV for your travel expeditions.

Using the RV’s Battery

You can always pull power from the engine when traveling in an RV. There are two ways to do it:

1. You can plug a 12-volt inverter into the cigarette lighter socket and supply power to your gadgets. Most inverters usually have several ports to charge AC and DC-powered appliances.
2. You can also connect an inverter directly to the RV’s battery. When using this method, you must keep your engine running to keep your battery from dying.

Using Shore Power

Most RV campsites offer shore power for a fee. You can use shore power to directly run your appliances like TV, microwave, and refrigerator or recharge your batteries.

Using a Generator

You can also use a generator to power your RV. Depending on the size of your generator, it can offer enough power to run all your appliances, including TV, dishwasher, microwave, refrigerator, and even an RV AC unit.

If you’ve limited space in your RV, you might want to consider alternative generator options. They also produce harmful emissions, which aren’t good for you and the environment. Another drawback of using a generator is its smell and noise, which are generally disliked by fellow campers at campsites.

Note: Some campsites and regions like national parks do not allow diesel and gasoline generators. Therefore, we advise you to check that the region you’d be camping in allows generators.

Using an RV Alternator

An alternator is a generator that converts mechanical energy into alternating current. When running, the RV’s engine spins the alternator and charges the battery, which powers the electrical appliances. However, the alternator isn’t a reliable way of producing power since it quickly wears out with usage. Hence, it should be used only as a backup option.

RV Air Conditioning Options

RVers have little choice when choosing an RV AC because they usually come pre-installed in the rig. Manufacturers generally install them depending on the RV’s layout and price point. However, if you have the choice to pick an RV AC, here are some options you should consider:

Rooftop AC Unit

These are the most common types of RV air conditioners. Since they’re installed on the roof, they don’t take up space, which is quite limited in an RV. Rooftop ac units are reliable and can quickly cool off your rig’s interior.

Portable AC Unit

If your RV doesn’t have a rooftop AC, you can consider investing in a good portable ac unit. They are powerful, affordable, and easy to set up. The downside of a portable unit is that it takes up precious space in the RV.

Window AC Unit

You can also choose the traditional window AC to cool your rig. They are the least aesthetic and not as popular as other options among RVers. They take up precious window space and may require foam board insulation between the AC and window frame to prevent it from rattling when the rig moves.

Under-bunk AC Unit

Under-bunk AC units are installed under the beds, benches, or storage spaces within the RV. The air from under-bunk units can be circulated right to the corners of the RV through flexible ducting. These AC units have their own advantages but aren’t suitable for every application.

RV Insulation

RV insulation is an often overlooked aspect of RV setups. It traps the cold air inside the rig and keeps warm air out. RV insulation can significantly lower your AC consumption by keeping your rig’s interior cool for a long period of time.

There are several insulation options to consider, depending on the size of your RV and the amount of insulation you need. Each insulation option has an R-value that refers to the material’s thermal resistance. A higher R-value indicates a higher resistance to the flow of heat.

Based on the R-value, here are the popular insulation options for RV:

• Fiberglass insulation
• Spray foam insulation
• Rigid foam insulation

These options can insulate the RV walls, windows, vents, and compartments.

Alternatives to RV Air Conditioners

Hot weather can be a challenge for RVers without an AC, but there are alternatives to keep your RV cool on the road. If you’ve limited roof space or budget, you can follow these tips to keep your vehicle’s interior cool.

Park in the Shade

The location where you park your RV can affect the temperature inside your RV—Park beside a shady tree or some other shelter to mitigate the impact of the sun.

Ventilation

Make sure you’ve enough ventilation in your vehicle. The goal is to pump warm air out and get fresh in the RV. Ceiling vent vans can help move the air around the RV.

Switch to LEDs

The halogen lamps that come standard in an RV emit much heat. Replacing these lamps with LEDs can greatly impact the RV’s interior temperature.

Use a Portable Air Cooler

Portable air coolers are lightweight and require minimal power to operate. They often come with dual voltage circuitry and can be powered using the RV’s DC cigarette lighter.

Final Thoughts

Running an RV air conditioner using solar power is absolutely possible. But it’s something that comes with a huge price tag. After reading this guide, you’re hopefully in a better position to determine the amount of power you’d need to run the air conditioning unit. And if you think using an AC with solar power isn’t worth the investment, you can use the alternative options to keep your RV cool.

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