Currently, few RV manufacturers include 12-volt air conditioning systems in their factory line productions, with the exception of Coachmen (Galleria model). However, custom-designed RVs, such as Class B and Class C units, may include the option of having 12v systems as part of the customization package.
RV manufacturers still use 120v systems that require a 12v thermostat and have not switched, yet, to full 12v systems. Dometic and a few other manufacturers now offer these 12v air conditioning systems for RVs, but the use of them is not mainstream and is done as a retrofit of units where the air conditioner needs to be replaced, or custom design basis.
However, if your definition of an air conditioning system includes a “swamp cooler,” or evaporative air conditioner, there are many more RVs that can, and do, use these adaptations of conventional air conditioning.
This system blows hot, dry air through a wet cooling filter or pad, which absorbs the heat and causes the water to evaporate, cooling the RV. But, this type of system increases the humidity in the RV. If you are in a drier climate, such as Nevada, Alberta foothills, or Arizona, these systems work well, but if you are in a humid environment, such as coastal regions, Florida, or even southern Mexico, they are very inefficient.
In most parts of North America, outside the listed areas, evaporative coolers are not the ideal solution. Yet, they are common in many household air conditioning installations. Evaporative coolers often run on 12v, because they do not use a complex, energy-draining compressor system.
How Much Cold Air Do 12V Air Conditioners Produce?
The largest 12v standard RV air conditioning units on the market produce 20,000 BTUs of energy, which is enough to cool a 35 – 40-foot trailer. Coachmen provide this Pro Air 12v air conditioner as standard equipment in its Galleria model (visit Coachmen Galleria page).
This is rather arbitrary, however, since other factors play a role in the cooling effect, such as the insulation and windows in the trailer, the average outside-to-inside temperature difference, whether your RV is in direct sunlight, whether you cook inside the RV, and how many people use the trailer at one time.
Traditional RV air conditioners are sized at about 13,500, while many of the 12v AC models available range from 8,000 to 12,000 BTUs.
How Much Power Do They Use?
A 13,000 BTU 120v air conditioner will require 3.81 kw to operate, while a 12v system will require up to 70% less, or between 1.21 kw and 2.48 kw.
A 120v AC unit consumes 10-15% more energy than a 12v unit because it requires the energy to invert power from 12v d/c to 120v a/c current. As well, the 12v systems use a high-efficiency compressor. The 12v units do not require as much “surge power”—the extra push of energy required by 120v systems–as they power up their compressors.
Manufacturers like Nomadic claim that their 12v systems are 70% more efficient than 120v systems. Many people that want to run their air conditioning on batteries and solar panels opt for this more efficient custom design option.
Can You Run A 12V A/C On Lithium Batteries & Solar?
Not only can 12v A/C systems operate on lithium batteries, but these batteries are much better suited to the application than the old lead-acid batteries. Solar can charge lithium batteries or lead-acid, but require sunlight hours to operate, sunny days to get the most power out of each solar cell, and temperatures below 21-25C to avoid the reduction in the conversion potential of solar cells.
With a large enough solar panel array and enough battery storage, your solar/lithium battery combination can run your RV air conditioning all day, AC or DC, but the cost of these storage systems is significant.
Lithium batteries are designed to be able to draw down to almost zero reserves, while lead-acid batteries do not draw down below 50% capacity. Even if both batteries had the same efficiency and same weight, you would need twice as many lead-acid batteries to do the same job as a lithium storage bank.
Using lead-acid storage also carries the burden of exceptionally high weight, and the amps generated per pound of battery are considerably less than lithium batteries. Solar panel arrays also take up a lot of space, requiring an open area with access to direct sunlight most of the day to be effective.
The evolution of battery technology means there are a variety of choices for solar storage. Read more about Different Types of RV Batteries here.
For more information on solar panels, we answer 13 Questions About Solar Panels.
How Big Of An RV Will They Work On?
A single 12v 13,000 BTU air conditioning unit will comfortably generate enough cold air to cool a 32-foot trailer, if the trailer is not parked in full sun, if the inside temperature is to be cooled to less than a twenty-degree difference to the outside air if it has a lighter-colored exterior, is built to contemporary standards, and only a few people use the trailer regularly.
To maximize the cooling effect, close doors to rooms not in use and shut the vents in those rooms. This zone cooling reduces energy, by only cooling the rooms that you have not closed off.
Many of the larger RVs have two air conditioning units, however. Two AC units will cool even the largest RV. The cost, though, is in electrical consumption, making a solar/battery power plant virtually inviable. Even most camping sites do not provide sufficient electricity to power more than thirty amps of the draw, and bigger RVs often use 50 or more amps.
Wikipedia provides information on how your air conditioning system works.
What Are The Downsides Of 12V A/C Units?
The cost of the unit, current draw, and size of available units are the main drawbacks of 12v AC systems for recreational vehicles.
These 12v air conditioning systems cost between $1,000 to $7,000, plus the cost of heavier wiring for the dedicated AC system and solar panel plus battery banks (if you intend to go off the grid), at a cost that may exceed $4,000. Compare that to 120v systems that cost between $900 to $1,700 and have larger cooling capacities (BTUs).
The lower voltage and similar current draw of 12v AC systems versus 120v units mean that your RV will require much heavier wire to handle this new, dedicated current demand. In addition to cost, there is the problem of rewiring a trailer that is not designed to be retrofitted in that manner.
At the present time, the largest available 12v system is 15,500 BTUs, but most units are between 7,600 and 11,000 BTUs—well below the recommended size of 13,000 for a standard thirty-two-foot trailer.
What Models Are Available Today?
There are only a handful of manufacturers offering 12v AC for RVs, including Nomadic Cooling, Dometic, Indel B, Pro Air, and Rigid. RV evaporative coolers are available from Turbokool. All of these units, as of 2021, were add-on units, not included as standard equipment with any RV models.
Custom campers, though, maybe purchased 12v AC systems as part of the conversion kits. While these conversions usually involve only van-style campers, some of the Class C conversions also offer 12v installations.
Is The Future Going To Be 12V A/C Units?
Whether 12v AC systems become common depends on the retrofit/repair market, because currently, no manufacturers have moved to installing these systems as original equipment, making general use less likely.
Since RV air conditioners often last only five years or so, consumers may choose to retrofit their units with 12v systems, rather than the heavier, noisier 120v units.
On the other hand, if buyers move more to boondocking or wilderness camping with smaller RVs and trailers as a camping option, there may be more of a demand for off-the-grid AC that 12v systems provide.