As the weather heats up you may be dying for an air conditioner to keep cool in your campervan this summer. But what to get? And how to run a power-hogging A/C? 

First the good news: power-hogs are no longer your only A/C option. The newest A/C models are making all the difference for campervans.

Traditional RV rooftop air conditioners are alternating current (AC) units that provide plenty of cooling power, most often rated for 13500 BTU to 15000 BTU. They are also quite inexpensive for the amount of cooling power they offer. Some of these popular RV rooftop air conditioners:

However, they have some drawbacks:

• The air conditioner needs a large AC load, so you need an inverter to convert your van’s DC battery power to AC, and that inverter must have a surge rating (ie, ability to provide power for a very short amount of time) high enough to cope with the huge startup power surge.

• The continuous power use of an AC air conditioner is so high you must either have a small generator (eg, Honda EU2200i, Yamaha EF3000, etc.) or an AC power source (eg, 30A or 50A power plug-in at a campground or RV park). Otherwise your van’s battery bank would get drained very rapidly.

• Most of these have a large footprint, taking up critical roof space needed for solar panels or gear storage. They are often quite tall, generating drag or wind noise.

New High-Efficiency Models

However, things are changing! A few new models draw much less power at startup, and they use so little power, they can run off your solar panels while your van engine is off. So now you can keep cool even if you want to go way off the grid and stay off for weeks.

Some of these newer models include the Dometic RTX2000, the Nomadic 2000 (75 amp or 100 amp compressor options) and the Kingtec KTD2. They run off of your battery bank and without a generator or a hardwired inverter. See this table for a side-by-side comparison of three amazing air conditioners: 

The sleek  Dometic RTX2000 requires low power draw. This roof-mount unit is very quiet and has a 2000w cooling capacity.

The Nomadic 2000 comes in white and also mounts on the roof for a low-profile look. This unit uses less than half of the energy that older models used -- only 12v DC power -- so it can run directly off your 12v battery bank without an inverter. 

The Kingtec KTD2 requires so little power that it can run off your van’s house battery bank and allow for hours of cooling without being plugged in. This 12v air conditioner is very electrically-efficient, providing 9800 BTUs of cooling while using at most 48A@12VDC. This unit is low black and low profile and attaches to the top of your van for an incognito look and quiet cooling. 

Use this BTU calculator to decide which of these air conditioners will work best for you based on the size of your van and the power of the air conditioner. Tips: use "poor" for insulation, estimate total cubic footage of your interior space to be heated or cooled, and estimate maximum/minimum cooling or heating BTUs needed.

Batteries Required

If you want to run your DC-powered RV air conditioner off-grid, you’ll need to do it with stored power from your RV battery bank. You’ll need a lithium RV battery bank (rather than AGM or lead-acid), for several reasons:

• Lithium batteries can drain down very low without damage, whereas lead-acid batteries won’t last if they’re discharged more than 50%.

• Lithium can recharge five times faster, while those lead/acid batteries only charge at a C/5 rate (ie, if it’s a 100 AH battery, it can only have a max 20A charge). Many lithium batteries can be charged at a 1C rate (ie, a 100Ah battery can charge at 100A). This is vital in order to get power rapidly back into your batteries.

• Lithium batteries are much smaller and lighter, so you can fit more amp-hour capacity in your van. We typically recommend at least 400-600AH for battery banks being used to run DC RV air conditioners. They run about half the size and a third the weight, especially since you have to buy twice as much capacity in lead-acid/AGM to get the same capacity in lithium batteries, because of the 50% depth-of-discharge (DOD) limitation with lead-acid deep-cycle batteries.

Power Options

For these newer DC-powered air conditioning units,  you’ll be drawing DC power from the RV battery bank, rather than hooking up a generator or shore power. So how do you get power back into your batteries? We recommend having one or two charging sources, either a battery-to-battery charger or rooftop solar, or both. 

The modern crop of battery-to-battery chargers, like the Sterling  BB-1230 or BB1260 and Victron Orion TR, are able to handle the combination of dissimilar-chemistry batteries that are in use in many RVs today. Battery-to-battery chargers need to be matched to the alternator size of your vehicle (and manufacturer limits), since they are drawing power from the alternator. You do not want to exceed 50% of the alternator size in charge output, for example a 180A alternator should have a charger drawing no more than 90A.

For a rooftop solar system you have several choices, including the Samlex, Zamp or Go Power systems. These high-powered tempered glass units are typically sized suitable for most van roofs (if you have a large RV you can get many larger units for higher power usage). These require solar charge controllers like the Victron which you can operate remotely using a phone app or the internet.  These solar powers use lithium batteries as well.

If Shore Power Is Your Thing

All that said, if you will mostly have access to shore power, such as in campgrounds, or if you prefer to have a generator, previous generation models are still widely available. If that’s more your style, check out the Dometic Penguin II which requires a 3000 GW generator and cools up to 11000 BTU. 

These days there are many high power, efficient options for air conditioners as well as older units that will keep you cool this summer no matter where you might be traveling. If you are interested in package and kit options see our next blog post for more information (coming soon).