RV solar

RV Solar Power for Air Conditioners

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Dry camping is becoming more popular as technology advances. Specifically, RV solar power has allowed those living the RV lifestyle to make their own roads and find their own campsites. One limitation that remains a problem is running air conditioning units off RV solar panels.
It’s possible to run your RV air conditioner off of a solar system with the right equipment. There are a couple of questions one must ask themselves before attempting to do so.

  • Can I afford it?
  • Does my RV have the capacity to fit the batteries and solar panels I will need?

The problem boils down to the fact that air conditioners require a massive amount of power, and solar panels have a low charging rate. We’ll explore overcoming this obstacle in our discussion, but it does not come small or cheap. To make this point, let’s take a look at just how big a solar system would have to be to run your RV air conditioner for just five hours a day.

How RV Solar Panels Work for Your RV

For this article, we’re going to give you a brief overview of how RV solar systems work. For a thorough description, you can view our article that goes into the basics of RV solar components. You can also check out our article on calculating how much solar you need and understanding electrical measurements.

Solar panels don’t directly power anything on your RV. Instead, they charge your house batteries. The batteries connect to your direct current (DC) fuse box. For the AC to run correctly, the battery is wired to an inverter which turns the electrical current from DC to AC and sends it to the AC breaker/fuse box. The fuseboxes supply the power to all of your components or outlets. Within the fusebox, some fuses look like various colored two-pronged plugs or black switches called breakers. These act as safeguards to prevent overcharges from damaging your devices.

Main Components of RV Solar Power

When you set up solar on your RV, there are five different components you need to have it work correctly and safely.

  1. Solar Panels: You will want to look for the highest-rated panels on the market. Since you have limited space and your A/C units require a lot, you may want to choose the higher wattage panels. Panels come in 100-600 watts. They come in flat panels that you can install on your RV roof or place on the ground with stands. There are flexible panels that stick directly to the roof.
  2. Solar Charge Controller: This is the brain of your solar charging system. Its job is to regulate the voltage supplied to your batteries from the solar panels. It should also reduce the voltage to a trickle charge when the battery is fully charged to prevent overcharging. There are a couple of types, but if you plan to run an AC using a solar system, an MPPT type is probably the best option since it has more efficient charging than other types.
  3. House Batteries: Solar panels only charge your house batteries. All of the electronics draw their energy from the batteries. Lithium-ion batteries are probably the best option for RVers who want to create a solar setup that will run their AC for any considerable amount of time. Learn more from our discussion about batteries.
  4. 4,000-Watt Inverter: The inverter is the opposite of your converter. It takes the DC power from your batteries and changes it to AC power. We recommend the 4,000-watt unit since your A/C units, and other devices will draw a massive amount of power at one time.
  5. Solar Power Meter: Installing this measurement device will allow you to monitor how your panels are operating at all times. Knowing your voltage, watt, and amp readings can alert you to possible issues that need attention.
  6. Battery Meter/Multi Meter: Checking the input and output of your batteries can be essential. After years of use, batteries can lose their ability to charge, leak, or other problems can occur. Checking them periodically is a great preventive maintenance practice.
  7. A/C Soft Starter: Allows air conditioning units to start with significantly less power. More A/C soft start info below.

You will also want to adjust the DC and AC sides of your fuse/breaker boxes for the additional components you are adding. Your batteries will feed directly to the DC parts of your electric system. For the AC side, the power starts at the batteries, flows through the inverter, goes to the AC fuse box, and then to the various points in your RV.

Running the Numbers

Before we start throwing numbers around, let’s talk about the formulas used to get them. For a detailed explanation of how these formulas work, check out this article detailing how to figure out your solar power needs.

When determining the amp draw of a 120V appliance, Amps = Watts / Volts. So to figure out the amp draw of a 60W lightbulb running on 120V, it would look like 60W / 120V = 0.5 amps.

When you run a 120V appliance with your 12V batteries, the power must first be converted from DC to AC in the inverter. The inverter uses a little bit of extra power to run the same 60W lightbulb because it is not 100% efficient. Most people figure this to be about 15%. The formula looks like the following.

(60W / 12.6V) / 0.85 (inverter inefficiency) = 5.6 Amps

Note: This article will use 12.6 volts to represent a full(ish) 12V battery. You should not drain lead-acid deep cycle batteries past 50% (12.2V) regularly to avoid damage to the battery.

Air Conditioners

There are many different sizes of ACs which use a different amount of wattage. The average RV AC is a 13,500 BTU unit which uses about 2,750 watts to start and 1,250 watts once up and running. To get an average, we will split the difference and say it uses around 2,000 watts to run.

To run one 13,500 BTU air conditioner for five hours a day, you are using 2,000 watts for 5 hours. Let’s figure out how many amps that would draw from a 12V system with an inverter.

(2000W / 12.6V) / 0.85 = 187 Amps

Finding the Amp-Hours

Most batteries are rated in amp-hours (Ah), so to find out how much battery power we need, we multiply the amperage draw by how many hours we intend to run the device. In this case, that’s 187 X 5 = 935 Ah.

So to run your AC, you would need batteries with a super high amp-hour rating in your battery bank. For the 12V lead-acid deep-cycle style, that would be at about eight Group 8D AGM batteries with a 245Ah rating. That is a bare minimum amount of lead-acid batteries.

Eight 8D batteries weigh about 1,200 lbs, which is why lithium-ion batteries are the way to go. They can reach around 100% discharge without any damage to the batteries, and they are much lighter. For this application, you would only need a minimum of five 200Ah 12V lithium batteries totaling 300 lbs.

Before you start shopping for five lithium batteries, keep in mind that this amount of battery power is just enough to run your AC about 5 hours a day. It doesn’t figure out the amount of power you will use for other devices or any reserve power you may want for cloudy days. You may still want eight 200Ah lithium batteries for a total weight of 480 lbs.

Solar Panels

So we want to run an air conditioner for 5 hours a day for a total of 935Ah, or about 10,000Wh. To make life easy, you can use a handy calculator online to help with battery bank size and the number of solar panels needed. According to one such calculator, you would need seven 400 watt solar panels with a charge controller that can handle 234 amps. That would add about 350 lbs to your rig, assuming you have the roof space for the solar panels.

Setup costs for a solar system this big are considerable. You can expect to pay over $10,000 to run your air conditioner and all the other components together. The ideal setup for a 13,500BTU unit would need:

  • Seven or more solar panels that are at least 400 watts
  • A bank of at least 6-8 12V lithium batteries
  • A 4,000-watt inverter since over 3,000 watts can be running at one time
  • An expected project cost of well over $10,000

Is RV Solar Power Right For You?

Many RVs lack the roof space to accommodate the solar panels needed, let alone the storage space for the battery bank size required to run their AC for any reasonable amount of time while dry camping. Before you write off solar because of the extreme cost and hurdles of running your AC with it, remember that solar systems on RVs are great for many other applications. Here are some boons and burdens to think about.

Boons

  • Clean, renewable energy
  • Low maintenance
  • Longer off-grid independence
  • Great for dry camping
  • Ideal for full-time RV lifestyles
  • Have electricity wherever you go

Burdens

  • High startup cost
  • Weather dependent- Many cloudy days may prevent proper charging
  • Lose storage space due to the battery banks and electronics
  • Panels create heat that air conditioners may have to fight against
  • Adds additional weight to your roof and storage bays

Things to Keep In Mind

You Will Need an A/C Soft Starter

At times, the only way you will get one or more of your RV air conditioners started while on RV solar is by using an RV soft starter. An A/C soft starter helps provide that initial power surge needed to start the air conditioner on your RV. Very often, your RV solar system is perfectly capable of running the A/C. It just can’t start it. That’s where SoftStartRV comes in. By self-installing a soft starter for each A/C unit on your RV, you’ll find much greater success keeping cool while boondocking or on limited power.

SoftStartRV is an excellent investment that helps run your AC off solar, a gas generator, or campground hookup. It’s also easy to install. Check out the video below to learn more.

Have a Secondary Power Source

There may be times where your solar system doesn’t fully charge your batteries. It could be from many days of bad weather, overuse of electricity or your panels becoming dirty. Having a backup source to give you the extra charge is always advised. Many motorhomes have secondary alternators that connect to the house batteries. If not, the primary alternator charges both the house and the engine batteries. Fuel generators and shore power electricity also charge them.

Are there creative RV solar solutions?

There are many ways you can run A/C units at lower wattages. As you can see in this video, they use a portable window unit that uses 410 watts instead of their factory-installed units. They use two of these units in their RV at the peak of the day. As the day ebbs, they end up turning one-off due to the inside temperature becoming too cold.

There are also reports of people using Tesla car batteries for a higher voltage battery bank. For example, two Tesla 24V batteries are equal to about eight or nine 12V batteries. However, this type of system should be professionally installed since you can’t just hook 24 volts up to your RVs 12V system.

Should I start with an RV solar kit?

Basic RV solar kits come with either one 100-watt or 170-watt panel, a small inverter, and one battery. If you want to run your air conditioner, these kits cannot handle the required amount of power needed. They’re limited to handle TVs, coffee makers, cellphone chargers, and other small devices.

Do RV solar panels add heat?

Solar panels do get hot. Their heat does transfer to your roof and can transfer that heat inside your coach. Some people that have installed flat panels leave enough room between the panel and their RV roof to let air flow through to stop heat transfer. This also cools the panels.

Are there RV air conditioners that take less energy?

There are various makes and models of air conditioners on the market. Rooftop installed units generally range between 13,500- 16,000 BTU. They’re designed to cool the required space in an efficient way.

Is RV Solar The Right Way For Your Air Conditioner?

Solar technology has opened up a lot of doors for the RV world. It has allowed more possibilities for off-grid camping. The possibility of running your air conditioning unit on solar power is an expensive proposition still, and many RVs can’t support the necessary equipment. For those that live full-time in remote dry camping situations, this may be a great option, especially if they stay in locations where there are many clear sunny days. This solar setup pays for itself by cutting generator fuel costs.

If you are a part-time camper, it may not be worth the effort yet. Even if you want to decrease your carbon footprint, the costs of a campsite with hookups or running your generator are not financially sound right now. There are other money and carbon-saving ways you can do so. Our recommendation is to keep an eye on the industry. As technology advances, the big names and the small start-ups are always coming out with something new each year. 

Some high-end travel trailers and RVs utilize lithium EV batteries to produce off-grid-ready RVs that can run the AC off solar. As the price of EVs comes down, so too will the cost of installing these systems in RVs.