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.