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How to Run RV A/C on Batteries (Without a Generator)

The ultimate off-grid camping experience would include running RV AC without a generator, right! Unfortunately, it can be costly when considering how many watts/amps an RV AC uses and how many batteries it needs to run. However, there are things that can be done to make it possible. In fact, I am writing this from a cool camper on a 90-degree day without a generator!

Writing a blog post from a solar powered air conditioned RV
Real-time photo snapped as I write this article! Were in our truck camper (video below) running a solar-powered DC air conditioner to stay cool.

How? Well, in today’s article, I will share exactly how we achieve this and some of the best options to date for staying cool anywhere you roam.

We’re sharing everything you need to know to make this dream a reality. Are you ready? Let’s get started!

What Goes Into an Off-Grid Power System? Overland RV Solar Power System With 12V Air Conditioning

How We Run AC Without A Generator

As I said above, I’m writing this from a cool camper, but it’s far from stock. There are three components to consider when running an AC off-grid. How you will generate your power, how you will store your power, and what AC unit you are using. In our case, we are running a large solar array, lithium batteries, and a highly efficient air conditioner.

We will get into the actual components we use and recommend in a bit but lets dive into some of the details.

Will an RV AC Run off Battery?

No, Stock RVs cannot run the AC off the battery. Typically, an RV AC will only run off the battery bank with significant modifications to the electrical system. AC units use AC power. Not to be confused, AC unit (air conditioning) and AC power (alternating current) or household current. Batteries produce DC (direct current) and cannot run most AC units directly. The easiest way to run an air conditioner is to install an inverter. These devices invert the DC power in the batteries into AC power. 

Whether it’s an AC or an electrical outlet for TVs, coffee makers, and microwaves, you can run it from your battery bank instead of your RV generator. However, power-hungry devices, like air conditioners, can chew through a battery bank very quickly.

Some 12V and 24V air conditioners can run off the battery bank. However, these aren’t cheap. You’ll be looking at spending between $1,500 to more than $5,000 for one of these units.

DC air conditioner

Unfortunately, you’ll also need to spend a few thousand dollars upgrading your battery bank. The standard batteries that come in most campers won’t last long. Lithium batteries are the only way to go if you want to run high power loads, as lead-acid has way too many problems. So while it may be expensive, it’s worth it to many owners if they frequently camp during hot weather.

How Many Watts Does an RV AC Use?

An RV AC requires a tremendous amount of power to run, which is why some people wonder if only a generator can do the job. The two most common unit sizes are 13,500 and 15,000 BTUs. When the compressors for these beasts kick on, there’s a massive surge in power. A 15,000 BTU typically requires 3,500 starting watts, while a 13,500 unit requires 2,750.

Once the initial power surge is over, the watts/amps for your RV AC are more manageable. A 15,000 BTU model requires approximately 1,700 watts, and a 13,500 BTU unit requires roughly 1,450 watts. Even running a single AC in an RV can require ample watts/amps.

It’s essential to recognize that RV AC units are inefficient. Many of these devices deliver as little as half the rated BTUs. Good luck staying cool if you’re camping during a heat wave. Unfortunately, it can feel impossible when camping in these conditions.

Thus if you want to stay cool in your camper, you really need a different AC unit than the one that comes with it. On our truck camper, we replaced the rooftop unit with a high-efficiency DC unit, but on our motorhome, we actually installed a separate temporary window unit for off-grid camping. We will talk more about this in a bit.

Interior RV AC unit
Window AC units are not know for being the most efficient, but they are sometimes better than RV rooftop units.

How Long Will a 12V Battery Run an Air Conditioner?

Knowing how long a 12V battery instead of an RV generator will run the AC requires a little math lesson because no two units will be the same. The general calculation is to figure out the power used by the AC and divide by the energy capacity of your batteries.

We wrote an entire article about calculating solar energy needs that covers the basics of this and more that we would recommend you read if you want an accurate answer.

Overall the equation is as follows.

(Kwh consumed by AC unit) * (Efficiency Loss Of conversions (inverter, batteries etc)) / (Kwh Capacity of battery Bank) * Pukert Losses

To get the Kwh of the AC unit, you need to know the running watts and divide it by hours. A rough guess for full load operation would be (running watts)/1 hour. However, AC units generally cycle on and off, especially at night so you might be low on your estimates doing this.

You then need to multiply the answer by the efficiency loss. When converting from battery power to alternating current with an inverter, you typically lose around 15 percent. So this would be a multiplication of 1.15

Next, calculate the Kwh of your battery bank. Generally, this is the amp-hour capacity * The nominal battery voltage. For lead acid nominal voltage is around 12.5 and lithium is around 13.

DC air conditioner installed on truck camper
This is the installation of our DC AC unit on our truck camper.

However, you must remember that lead acid batteries should not get discharged at less than 50 percent of their capacity. On the other hand, you can discharge lithium to 100 percent, but we typically try to keep ours above 20.

Lastly, you need to consider the pukert exponent if you will be discharging your batteries hard. Your battery manufacturer will be able to provide this number, and it is a loss from the batteries at high loads. Lead acid once again fails under high loads because of large internal losses.

Remember, the starting wattage will be significantly more than when running. As the unit cycles, it will require less power and can run longer off your battery bank. The more amp hours of battery you have, the longer you can stay cool while camping.

How Many Batteries Do I Need to Run My AC All Night?

We cant give you a correct answer because, once again, you need to calculate how many batteries you need for your specific situation. Using the information in the above paragraph, you can figure out how many batteries you need to run your AC.

We use an ac in our bedroom that draws 600 watts of power. In a 10-hour window, this unit generally consumes around 4Kwh of power (it cycles on and off at night). This equates to about 3.5 of our 100Ah Battle Born Batteries.

However, remember that this only considers the power usage for your AC unit and assumes you’re starting at 100% capacity. Considering these additional factors, you’ll likely need an extra battery or two. If not, you could risk damage and wake up to a depleted battery bank.

We generally consume around 6 kWh of battery capacity in a night when running our small bedroom AC.

RV batteries
The more amp hours of battery you have, the longer you can stay cool while camping in your RV.

How to Run Your RV AC on Batteries

If you want to know how to run your RV AC on batteries instead of your generator you will need to modify your power system to include lithium batteries, extensive solar power, an inverter and ideally a high efficiency AC unit.

Upgrade to Lithium Batteries

The first thing we recommend is to upgrade your battery bank to lithium batteries. There are several reasons why lithium batteries are better than the standard lead-acid batteries that typically come with campers. For example, lithium weighs half as much, provides twice much power, and can last up to ten years.

Unfortunately, lithium batteries are very expensive. You can expect to pay around $1,000 per battery for 100 Ah. We’re seeing manufacturers come out with 200 Ah and 270 Ah batteries. However, they come with price tags between $1,700 to $2,500 per battery.

When making this upgrade, you may have to replace your charger. Lithium can accept substantially more power, which allows it to charge faster. Many standard chargers cannot handle the increased power. While it will likely charge your battery, it will take an incredibly long time.

Pro Tip: We tested different RV battery brands and uncovered which one was The Best RV Battery For The Money.

Consider Installing a Soft Start

A Soft Start device can reduce your RV air conditioner’s power needs. Many RVers use these devices to run multiple air conditioning units off a 30-amp connection. Without one of these devices, you’d only have enough power to run a single unit.

Installing these devices is a relatively straightforward task depending on your AC unit. However, it’s generally a project that anyone with basic DIY skills can handle. Take safety precautions and turn off all power running to your camper. Always test the power to confirm there are no hot wires before splicing into the wiring.

RV AC unit
Be prepared to make significant modifications to your RV’s electrical system to be able to run your AC.

Choose the Right Inverter

You need to choose an inverter for your RV AC based on your power needs regarding the watts/amps you use. If you will only run a single air conditioner and you install a Soft Start, you can likely get by with a 3,000-watt inverter. However, remember that you’ll need to manage your power wisely to avoid overloading it.

Installing a Soft Start on your AC to run it won’t do anything for your microwave, coffee maker, or other power-hungry electronics. The more capable the inverter you install, the less you’ll have to worry about what devices you’re using simultaneously.

Invest in Solar Panels

Invest in solar panels if you want to take your off-grid camping to the next level. Harnessing energy from the sun to recharge your battery is an incredible upgrade. The larger the RV, the more panels you can place on the roof.

Many owners love that their solar panels charge their battery bank as long as the sun is up. While cloudy days and shaded campsites can make it challenging, these panels often mean one less thing to worry about during your adventures. 

We don’t recommend trying to run everything on solar and having a generator backup, but you will be surprised how much solar panels + lithium batteries reduce generator runtime needs.

Pro Tip: Solar panels are a big investment! Use our Complete Guide to the Best RV Solar Panels to help make the right choice when buying.

Investing in solar panels comes with a hefty upfront cost, but will be helpful in ensuring you have all the battery power you need to run your AC.

What Are the Most Efficient RV AC Units

If you rely on your battery bank to run your RV AC, you’ll want to get the most efficient unit possible to conserve the watts/amps you use. You can choose high-efficiency RV rooftop units, but you will gain even more efficiency if you switch to a window or even a mini-split style Unit. Here are some of our top recommendations.

Truma Aventa – As AC units go, this is one of the most efficient and quietest rooftop units available… Available is a bit of a misnomer, however, because Truma does not sell this unit aftermarket, and you can only buy it factory installed… so for most, this is a skip.

Houghton AC (Rec Pro)- The Houghton AC is a fantastic, cost-effective, quiet, and efficient rooftop unit. While its efficiency is still not as high as alternative options its pretty good for built-in cooling. We have tested these units out and think they are the best rooftop unit available currently.

Nomadic Cooling or Dometic RTX (DC Power) – Have a smaller space that you want to keep cool with batteries? A DC-powered AC is going to be your best bet! While these are not the quietest units they will be the most efficient for solar power because there is no conversion losses in an inverter. These units are also fully variable, meaning they can vary the compressor to match cooling needs. No cycling on and off and much higher efficiency. This is what we are using in our truck camper, and it works fantastic off-grid.

Want a cheaper option, consider a window unit. While these won’t work going down the road, stationary applications can be a great choice.

Ukoke Mini Split Window Unit

Ukoke Micro Mini Split – We have tested this unit out and are blown away by its efficient operation and quietness. Inside we actually measured a far lower Db noise level than they advertise, making it perfect for sleep. We cool about 20 feet of our motorhome with this unit and it works great. 2 units might cool the whole thing with 1/5 the energy of the 3 rooftop units on the coach!

No products found.

Midea U Shape – This is another favorite AC of ours but its not a good fit for most RVs. If you can modify a wall or window, however, this might be a great option. Super quiet, high efficiency, and powerful, this is basically a full-blown variable mini split unit in a window AC package!.

Midea 10,000 BTU U-Shaped Smart Inverter Window...
  • ULTRA QUIET - The U-shape design of Midea U Smart Inverter AC...
  • MORE THAN 35% ENERGY SAVINGS - With the advanced DC Inverter...
  • SMART CONTROL - Midea U Smart Inverter AC is Wi-Fi enabled and...

If you want the ultimate efficiency going with a full mini split install will be your best bet for efficient cooling. These household systems’ efficiency blows away any RV or portable AC unit and usually can heat as well. We wrote an article all about mini splits if you want to learn more.

How Much Solar Do I Need For An RV or Off Grid Project: How To Get Accurate Calculations

Stay Cool While in Your RV

Summer is the peak camping season for many spots around the country. Unfortunately, as you likely know, it’s also the hottest time of year. Running your air conditioning unit off batteries will require extensive upgrades and investment, but it may be worth it.

Having the freedom to park your camper anywhere and still stay comfortable is a game changer. Don’t let the heat get in the way of you and your loved ones making some epic memories.

What’s your go-to way to beat the heat in the summer? Tell us your tips in the comments!


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About Tom Morton

Tom, a Pacific Northwest native, is our technical genius. Born in Washington and raised in Alaska before settling in Michigan. He's the man who keeps our operation running, both figuratively and literally.

With a background in Electrical Engineering, Tom specializes in RV solar systems and lithium batteries. He made history as the first documented individual to use a Tesla battery module as an RV battery. Tom has personally assisted countless RVers with system installations and has educated thousands more through his videos and articles.

Cinematography is another of Tom's passions, showcased in his work on the Go North series. You can see his camera skills on display in The RVers TV show on Discovery Channel and PBS where he also stars as a co-host.

Tom's mechanical expertise extends beyond RVs to boats, planes, and all things mechanical. He's renowned for taking on maintenance and repair projects single-handedly and is often spotted underneath RVs, making him the technical backbone of our endeavors.

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Steve Felt

Sunday 13th of August 2023

Battle Born batteries are overpriced, I went with a 100ah EcoWorthy lithium from Amazon for $350 and it keeps me off grid for as long as I need to be. Because my camper has a 12v only fridge it drains power on warm days so I run the Predator 3500 inverter generator at sunset to top off for the night if my 270 watts of Solar doesn’t get me above 80%. I am going to add a second battery though just to be able to be off grid longer and use less gas with the generator. I saw that they offer a 260ah lithium battery but I don’t know if that would complement the other I already have.

Raymond

Sunday 25th of June 2023

Shop around, especially look on Amazon and you'll find good prices and lots of choices for lithium batteries, solar panels and inverters. You don't need the top of the line $1000 batteries. You can get excellent batteries for half that but just make sure they have a built in low temp cuttoff which prevents them from being charged when the battery temp gets below 32 degrees which can damage them. If you buy an inverter, make sure its pure sine wave. Also, the ones that have a builtin automatic transfer switch are nice so you don't have to deal with plugging in extension cords, etc. Most of those inverters offer a remote panel so you can manually turn it on or off by pushing a button inside your camper. When buying solar always get a mppt charge controller (its much more efficient) and make sure its larger capacity than the system you're starting with so you'll have the capacity to add more solar panels in the future. It's better to buy individual panels and charge controller so you can customize your setup. Most "solar kits" don't have the capacity to add more panels and their included wires are minimal thickness so if you wanted to add more panels later on you might have to change to thicker wires and a larger charge controller.

Ralf

Saturday 24th of June 2023

Another informative article, thank you.

Please spot check: "We generally consume around 600 kWh of battery capacity in a night when running our small bedroom AC." I am guessing that should be 6 kWh?

Keep up the great articles and sharibg your adventures! It is appreciated! - Ralf

Mortons on the Move

Wednesday 28th of June 2023

Ha Thanks, Yes