The inverter–simplified!

An inverter is a bit of RV technology that often baffles people. But like solar and other things we’ve explained in this blog, it’s simpler than you may think.

What the inverter does and where to find it in your Airstream

An inverter is a device that allows you to plug things into electrical outlets even when the trailer itself isn’t hooked up to campground power. For instance, charging your electric toothbrush when you’re enjoying a quiet boondocking spot far away from everything.

Normally, when you’re using only battery power, you can’t run something that you have to plug in. But the inverter makes this possible, through a little electrical trick: it turns the power from the batteries, which is 12 volt Direct Current (DC), into 120-volt Alternating Current (AC),* which is the same power you use in your house. With the inverter switched on, you can watch TV, play DVDs, and plug in your laptop, even if you’re not hooked up to campground power.

If you’ve got a late model Airstream (except Basecamp and Bambi), it probably has a factory-installed inverter. There’s a little control panel on the wall with a push-button to turn it on and off, like the photo to the right.

Other Airstreams might have an inverter too, but those are usually owner-installed.

How to use the inverter wisely

This handy device does have a few limitations, so let’s cover a few essentials for using it wisely. I’ll keep it simple, without getting into technology terms or complicated math.

1. Use inverter power sparingly.

You can run out of power if you’re not thoughtful about how long you keep the inverter turned on.

The inverter runs off the batteries in your Airstream. The factory-installed batteries are designed to support the Airstream for a day or two of “typical” needs. So realistically, if you use your laptop computer all day, there won’t be much power left for the next day unless you also have solar panels or a generator to recharge the batteries.

Also, the inverter isn’t particularly efficient. It wastes up to 20% of the power, so there’s a larger hit to the batteries than you might think, whenever you use it.

If you’re a frequent off-grid camper and heavy user of the inverter, you might want to talk to a good service center about adding more battery capacity.

 

2. Use only low-power appliances.

The standard inverter installed in an Airstream has a rated capacity of 1,000 Watts. That’s plenty for low-power devices like the TV, DVD player, toothbrush charger, or a laptop, but not nearly enough for some other appliances.

Here’s a rule of thumb: if it has a heating element, don’t try to run it from the inverter. This includes a hair dryer, toaster, coffee pot, space heater, waffle iron, etc. You might get away with it for a little while, but eventually, the inverter will overload and shut itself off—or burn out permanently.

Another rule of thumb: if it has a motor, think twice before using it. Most things with electrical motors need too much power. This includes the air conditioner and microwave (which aren’t even connected to the inverter, so they simply won’t go on), vacuum cleaner, plug-in fan, etc. At the very least devices like these will drain the batteries quickly, and they might overload the inverter.

 

3. Every appliance has a useful label.

Not sure if the device you want to plug in is safe for the inverter? You can easily find out. Every electrical device has some sort of labeling to tell you how much power it needs. For example, this is the label printed on my Macbook’s charger:

I apologize because this involves a tiny bit of math. You need to know that by multiplying Amps and Volts, you get Watts. (I promise, that’s as hard as it gets.)

Looking at this label, we see “Input: 100-240V”. That means this charger will operate on any voltage from 100 to 240. (That means you can use it in Europe!) In North America, it will run quite happily on 120 volts.

We take that number and multiply it by the next number. If you squint you’ll see that it says “~1.5A” which means it draws a maximum of about 1.5 amps.  So by multiplying 120 x 1.5, we come up with 180 Watts. That’s way below the 1,000 Watt rating of the inverter, so now we know there will be no problem using this charger.

Just for geeky fun, you might take a look at a few other items you might plug in, like a coffee maker. You might be surprised (dare I say “shocked”?) by the range of power requirements.

 

4. Turn the inverter off when you’re not using it.

Even in “stand by” mode with nothing plugged in, the inverter uses power. It’s not much at any given moment, but like a dripping faucet it adds up to quite a lot over the course of a couple of days. So only turn on the inverter when you really need it, and be sure to remember to turn it off again when you finish watching your movie.

 

5. Watch the heat.

Remember that 20% power waste I mentioned earlier? It goes up in the air as heat. The inverter has a pair of fans to keep it cool, but on a really hot day it can get too hot—and that’s bad for the longevity of the inverter.

Most of the time this won’t be a problem. But if you pull into a boondocking spot after a sunny day of towing and the interior of the Airstream is over 104 degrees F (which happens pretty easily in the southwest), the inverter will be over its safe maximum temperature. Wait for the Airstream’s interior to cool down before you use the inverter. You can easily check the interior temperature by pressing the appropriate button on the Airstream’s wall-mounted thermostat.

 

6. Outlets can be handy while traveling!

Here’s one of my favorite hacks: when I need to add air to the trailer’s tires during a trip, I use a portable compressor plugged into  one of the power outlets on my Airstream.

Note that the outside outlet isn’t connected to the inverter on most Airstreams, so you may need to run an extension cord from one of the interior outlets.

I used tip #3 to compute that the inexpensive portable compressor I use draws just 130 watts of power. So even though it has a motor, it’s well within the capacity of the inverter. That means that anytime I need air I can just flip on the inverter and plug in my compressor. That beats the heck out of trying to find a plug or a gas station air compressor!

 

That’s probably more than you need to know about inverters—but hopefully enough to make you see that the inverter is a really handy device, and how best to use it. Like all good things, it’s best enjoyed in moderation.

 

 * The voltages mentioned are not exact. Household current, for example, can run from 108 volts to 132 volts and still be considered normal. The WFCO brand inverter in a late model Airstream is actually designed to output 115 volts. Likewise, a “12-volt” battery is really going to put out about 12.6-13.0 volts when fully charged. This voltage drops as the battery is depleted. You didn’t need to know this and it really won’t change anything written here, but I mention it because otherwise, somebody will feel the need to “correct” me.

Comments

  1. Dawn says

    Rich, I assume that if I use multiple appliances (i.e., laptop, a printer, TV, etc.) all at one time, I must add-up the total amount power being used which can’t be over 1,000 watts?

  2. Ronald says

    Thanks, this was very helpful. I have a 2018 FC 25′ FB. I have factory solar panels so deep cycle batteries.
    Can I run the propane heater off the inverter?

    • RichLuhr says

      The furnace in an Airstream runs directly from the batteries, so the inverter is not needed.

  3. Kim says

    I have a 2021 Caravel with the new Nova Kool fridge. Does inverter need to be on for fridge to run? Or just put batteries in “use” position?

    • RichLuhr says

      No, that fridge runs on 12 volt power directly from the battery, so it doesn’t require the inverter. However, the batteries will only power the refrigerator for a day or two, so it’s advisable to either be plugged in or get solar panels to augment the batteries.

      The battery disconnect switch should always be in the “Use” position whenever you are using or towing the trailer.

      • Patrick says

        To confirm, 2021 Bambi battery disconnect switch should be in the use position while towing even with 7 pin connected?

        • RichLuhr says

          Yes, that’s correct. If you have it in the Store position, the refrigerator won’t run while you are towing, even on propane.

    • RichLuhr says

      It’s possible to add an inverter to any Airstream, but the cost and difficulty varies. You should check with a competent shop that specializes in RV electrical work, to see what would be required in your Basecamp 16X.

  4. David Keeling says

    When the air stream is plug into 120v Does the inverter need to be turn on to charge the batteries I have a 27ft 2019 front twin

    • RichLuhr says

      No, the inverter doesn’t have anything to do with charging the batteries. That job is handed automatically by a separate device called a “converter” (confusing, right?) and it will always charge the batteries whenever the trailer is plugged in AND the battery disconnect switch is in the “USE” position.

  5. Krista Harris says

    I’m curious about the outside plug on our 2019 28′ International. Does it work on the inverter? I was under the impression it’s just the inside plugs.

    • RichLuhr says

      Correct, only some of the inside power outlets on your trailer are connected to the inverter. The same is true for most Airstreams. See my reply to Dennis Komeshak below.

    • RichLuhr says

      I’m using a very basic & portable one purchased at a Wal-Mart. There are many such available under $35. For occasional use, they’re fine. Just make sure they can handle at least 80 psi.

  6. Dennis Komeshak says

    Rich,
    Your last comment about the outside outlet has me confused. Are you implying that it is controlled by the inverter?

    • RichLuhr says

      Sorry, that was an error. My last Airstream did have an inverter-powered outside outlet but I realize that factory-equipped trailers do not, so I’ve updated the blog accordingly.

  7. Sherry says

    I was thinking JC advised to leave inverter in on status even when plugged into shore power. Not so?

    • RichLuhr says

      The inverter doesn’t do anything when you are plugged into shore power. There’s a thing called a “transfer switch” that just bypasses the inverter when shore power is available.

  8. Richard Fulton says

    Great information, thanks!

    I’ve been doing some roof solar panel testing to measure actual DC volts and amps from the factory panels on various sunny and cloudy days and found that simply turning on the inverter is an easy way to force an electrical load that will immediately cause the PWM solar charge converter to start charging, even if no other electrical load is applied. [No amps flow from the panels (no red charging light on the galley display), even on sunny days, if the battery is fully charged.] So yes, the factory 1000W inverter can be inefficient even with no other load plugged in to an inverter outlet….its loud cooling fan is a load all by itself.

    Unfortunately my 2018 Flying Cloud 25FBQ’s outside electrical outlet is not powered by the inverter circuit, only shore power. I confirmed this with a live test and reviewing the Airstream manual’s electrical circuit diagram. However you could still run an extension cord from one of the inside inverter receptacles to run your AC-powered tire pump if needed out on the road (or just buy a DC pump). Per my manual, the inside inverter outlets are each rated between 0.25A (30W) and 1.5A (180W) depending on the particular outlet (dining outlet is 1.5A), so check your pump’s watt rating which may well exceed that. The whole inverter circuit with multiple outlets is rated 15A, so not sure what happens if you plug in an AC appliance such as a tire pump rated more than 1.5A but less than 15A….if it blows just that one outlet’s breaker or the whole circuit’s breaker?

    • RichLuhr says

      This is great info, Richard. You’re right, the outside outlet may not be powered by the inverter on many Airstreams. I’ve removed this tip from the blog.

      Airstream also makes changes to wiring and appliances frequently, so it bears mentioning that ratings and capacities will be different from one trailer to another, so each owner should take a look at their Owner’s Manual for specifics.

      However, I think you may have mis-interpreted the “ratings” for the inside inverter outlets on your trailer. The numbers in the electrical diagram in the Owner’s Manual are budgeted loads, assuming a max circuit capacity of 15 amps. Each outlet is designed to handle the full output of the inverter. If they were really limited to 30 watts to 180 watts, you wouldn’t be able to plug much into them when you are using shore power.

      Each circuit (shown in the Owner’s Manual) has a separate circuit breaker, so if you overload any single outlet the associated breaker will trip and turn off all the outlets in that circuit. Individual outlets have GFCI breakers but those are designed to protect against electrical faults rather than overloads.

      • Richard Fulton says

        Rich, Thanks, that clears that up for me. I didn’t really understand how each outlet in the circuit could have its own separate amp rating as listed in the Airstream manual when there’s not a way for an individual outlet to blow vs. the whole circuit via the appropriate fuse for that circuit in the electrical control panel. 15A should be more than sufficient for even a big AC-powered tank-type tire pump like I use at home (I have a smaller DC-powered pump for the road). But having the outside outlet wired into the inverter circuit as you said would have been great for my trailer when out on the road or when boondocking and would save running an extension cord out there to power a pump, laptop, radio, etc.

        For boondocking purposes, I’ve been debating about upgrading my factory 1000W inverter to 2000W to handle any bigger AC appliances (e.g., microwave, portable heater) that can be operated on a standard 15A household outlet (air conditioning excluded)…..understanding that you gotta’ have the battery capacity (and battery recharge capability) to power the inverter if powering hungry AC appliances like the above for more than a short period .

  9. Frank Cates says

    I appreciate the inverter explanation in simple terms, as most folks buy a camper to camp & travel, not necessarily being grouped among the highly technical savvy folks. The AS has more advanced stuff than my older trailers (Sunline, Wilderness, Aristocrat…) which I had in the past. The AC/Heat controller is another thing-a-ma-jig that’s hard to get used to after previously having a simple thermostat for heat & cooling. So thanks for these tips.