RV Electrical Systems: Understanding How They Work
(Camp Addict does NOT accept payment from any company to review or endorse their products.)
First of all, please have a ton of respect for electricity. It CAN kill you. Yeah.
Do keep this in mind.
We will assume you have an RV.
Your RV has an electrical system.
Actually did you know that it has up to two or three types of different electrical systems?
Boy howdy, it sure can!
Don't worry, it may seem daunting now, but it will get easier once you are familiar with your rig.
This page is here to teach you all about your RV and its power systems.
You will become familiar with the 2-3 types of electrical systems in your RV and what powers them.
You will learn about 30-amp and 50-amp RV power cords and adapters that you may need, and MUCH more.
When it comes to your RV and electricity, there really is a staggering amount of information to know.
We are here to make it as easy for you to understand as possible.
Let's get down to it!
Need a new RV power cord? Parked too far from the power pedestal and need an extension cord? Looking for the right plug adapter? Click the button below to read our reviews.
Understanding Your RV Electrical System
Some things in your RV won't work unless you are connected to an external power source providing 120 volts of electricity.
Unless, of course, your rig has an inverter or is being powered by a generator.
What kind of things won't work unless using a generator or shore power?
Typically, your household outlets, your air conditioner, your TV (unless it's a 12-volt TV), and your microwave.
Usually, these appliances don't work off your batteries. Instead, these typically run off 120-volt power.
We are only concerned with the RVs power systems, not the RV ENGINE's power system (the automotive system) which you have only if you have a motor home.
Still, let's help you understand the difference between your two RV systems and the automotive system.
Motor Homes = 3 electrical systems
Trailers = 2 electrical systems
No matter what you have, when you plug into a shore power source, you are using the 120-volt system.
If your converter/charger is working properly, your RV batteries should also be getting charged.
Any 12-volt system will still be powered by your batteries.
Things like your lights, which could run off of your 12-volt system OR your 120-volt system will be powered by the 120-volt system.
Are you confused yet?
Let's dig a little deeper.
12-Volts? 120-Volts? Automotive System?
RRRRRR! What does it all mean?!?!?
We know you're probably not an electrician, so we are going to make this as simple as possible.
This should help you to understand the ins and outs of electricity and your RV.
It's not a complete course on electrical systems- we are just going to give you a basic understanding of how your RV works.
Here's a simpler explanation of some of the terminology we are using:
120-Volts: The power you get from an external power source. (I.E. NOT using your battery power.)
12-Volts: This is the power you get from your motor home or trailer battery or batteries. In my (Camp Addict co-founder Kelly's) travel trailer, I only boondock. This means I rarely have external, 120-volt power.
Therefore, I cannot run the things that require 120-volts such as my AC, my 120-volt TV, and the household outlets in my travel trailer.
Those items all require 120-volt (shore power or generator power) to work.
I do have a portable generator that provides 120-volt power, the same as shore power.
I use it to power up my batteries when it has been too cloudy for the sun to let my portable solar panels do the job.
12-volt AUTOMOTIVE system: (Motor Homes only) (Battery power) Pretend your motor home is simply an engine with no additional electrical parts.
Just like a regular car.
Your car, like your motor home, has a battery.
That battery and its components are a 12-volt system.
It starts your engine, turns lights on, powers your radio, etc.
That's the 12-volt 'automotive' system in your RV, and that's about all that it powers.
You have your RV engine battery, and you have your separate motor home 'house' batteries.
Your motor home 'house' batteries are part of your 12-volt RV system (below).
12-volt RV system: (Motor Homes and Trailers) (Battery power) This is comprised of the battery (or batteries) that power things inside the living space of your RV, or everything that is not your engine.
It powers things such as the 12-volt 'cigarette lighter' outlets and USB power ports in your rig, interior lights, water pump, likely your sound system, 12-volt TVs, and more.
It depends on what bells and whistles your RV does or doesn't have.
These batteries don't run anything related to the engine of a motorhome.
They only run some of the systems that make an RV an RV (the 12-volt systems)!
The 120-volt RV system powers all the other 'RV related' electrical stuff... your power outlets, 120-volt TV's, your microwave, air conditioner, etc. (non-12 volt systems)
Everything can be powered by the 120-volt system in most RVs (12-volt systems are powered by a 120-volt source via your rig's charger/converter).
But not all appliances/systems can be powered by your 12-volt system (battery power) unless you have an inverter.
You would need to be running a generator, or be connected to shore power for that.
You will have to learn the ins and outs of your particular rig- what systems are powered by what voltages.
Don't worry. It DOES get easy!
RV Plug End Types
All RV power and extension cords use plug ends that are compliant with the NEMA standards.
NEMA stands for National Electrical Manufacturers Association.
It's the organization that sets the standards for electrical connectors used throughout the US, Canada, and other countries.
This means that RV power cords are compatible with power pedestals, so there is never a case of, um, this 30-amp plug isn't fitting into that 30-amp receptacle.
They just work!
Below are the NEMA connectors that you will see in 30-amp and 50-amp RVs.
30-Amp RV Plugs
A 30-amp RV plug is a three-terminal design (hot, neutral and ground).
The male (plug) end has 2 straight blades (hot & neutral) and 1 round prong (ground).
The hot and neutral terminals are at 45º from vertical, and 90º from each other.
A 30-amp extension cord has a male end with a TT-30P plug and a female end with a TT-30R receptacle.
Are your eyes glazing over yet?
Wow, OK, let's continue...
A 30-amp RV power cord has a male end with a TT-30P plug and a female end with an L5-30R marine-style twist-lock receptacle connector.
The twist-lock connector is either available with a straight connector or a 90º connector (that reduces strain).
Notice how both the 30 and 50-amp plug types have either a 'P' or an 'R' at the end?
This indicates whether the end is a plug (male) or receptacle (female) end.
- P = plug.
- R = Receptacle.
See how simple this is?
We'll let you figure out on your own why the plug end is considered 'male' and the receptacle end is considered 'female'.
50-Amp RV Plugs
A 50-amp RV plug is a four-terminal design (hot, hot, neutral and ground).
The male (plug) end has 3 straight blades (hot, hot & neutral) and 1 round prong (ground).
The female (receptacle) end has 4 receptacles that match up with the male end's prongs.
A 50-amp extension cord has a male end with a 14-50P plug and a female end with a 14-50R receptacle.
A 50-amp RV power cord has a male end with a 14-50P plug and a female end with an SS2-50R marine-style twist-lock receptacle connector.
The twist-lock connector is either available with a straight connector or a 90º connector (that reduces strain).
Amperage Of Your RV
Your RV is wired for a certain amperage.
You will either have a 30-amp rig or a 50-amp RV and cord.
How do you know which yours is?
If you are unsure, it's super easy to find out!
Simply look at the plug on your RVs power cord, located somewhere inside an exterior door (if you have a fixed cord).
Or, look on the outside of your RV (if you have a detachable cord).
A 50-amp rig has 4 prongs.
A 30-amp rig has 3 prongs.
A 30-amp RV plug (3 prongs) will look like the picture below left.
A 50-amp plug (4 prongs) will look like the one below right.
At any given campground, there are USUALLY separate 120-volt outlets on a single power pedestal.
There's one for the 30-amp power cord and one for the 50-amp power cord.
However, sometimes you go to a park that only offers one type of plug, usually a 30-amp.
This is when an adapter becomes a necessity.
We're not going to talk about the specifics of RV power and the intricate details of electricity and power usage.
Learning more about power can be very detailed and complicated.
There are other more knowledgeable resources for figuring out how much amperage certain appliances take and what one can or cannot use at the same time.
This page is simply to learn about what cords and/or adapters you need and why, with a general overview of RV systems and electricity.
Connecting To A Power Outlet That Doesn't Match Your RV's Plug
What's an RVer to do in this situation?
The solution is easy.
You must have a 'dog-bone' or 'puck' style adapter to match your RV plug to the 120-volt outlet that you have access to.
Be aware, if you have a 50-amp rig, and you connect to a 30-amp plug, you won't be able to use as much amperage in your rig then if you were connected to a 50-amp outlet.
The same is true if you have a 30-amp rig and plug into a 15-amp (household style) outlet.
You can only use as much amperage as the outlet you are plugged into can provide
(yes, this should be common sense, but we figured we'd clarify).
However, say you have a 30-amp extension cord from your rig plugged into a 50-amp outlet
Yes, you will still have use of your full 30 amps.
It's simple math (or something like that) - there is no way you can squeeze 50 amps worth of power out of a 30-amp receptacle, but you certainly can get 30 amps of 'juice' out of a 50-amp outlet.
Don't worry, plugging your 30-amp (via a dog bone adapter) RV into a 50-amp outlet won't fry your 30-amp electrical system.
Because your 30-amp plug only has 1 'live' prong, it only accesses 120-volts.
No worries, 240-volts will NOT be going into your rig.
It doesn't work that way.
(Do NOT ever plug your RV into a household dryer plug, which looks exactly like a 30-amp outlet. Your rig will get fried...)
Do Not Plug Into That Dryer Outlet!!!
And Make Damn Sure Your Electrician KNOWS RV Systems!
The "modern voltage protection devices" that Mike Sokol mentions that could save your RV from damage due to incorrect voltage are Electrical Management Systems (EMS).
We discuss why you need an EMS for your RV, as well as tell you the best ones to purchase, in the RV Surge Protector guide.
Types Of RV Plug Adapters
There are two primary types of RV plug adapters:
Like anything else, both have their pros and cons. Let's look at the differences:
Dog Bone Adapters
The dog bone style is bigger so it takes up a little more room.
Space becomes a huge commodity in an RV.
Having a few dog bones can take up more space than the puck styles will.
However, they are more hardy and reliable than the puck style.
This makes them highly recommended over the pucks.
If you are always in a campground, you will want to have one for every scenario, so likely you should have at least 2 of them (appropriate connections for your rig's amperage rating).
Hockey Puck Adapters
The hockey puck style is not as reliable or as hardy as the dog bone styles are.
They tend to get hot while using them, so it's best to get the dog bone if you need to use one for an extended period.
The pucks are smaller though (above), so if you don't need to use them often, or for very long, you may be able to go with the pucks. You could also just have them for backups.
Want to know which plug adapters we recommend? Click the button below to read our reviews.
Why You Should Buy A Quality RV Plug Adapter
RV Extension Cords
Do NOT ever, EVER use a regular household/yard extension cord to connect to your RV!
This would be asking for disaster/fire/frying of your rig.
Here's a perfect example- The guy in the below video made three common mistakes.
1. He used a household extension cord that was WAY too small for his 50-amp rig.
2. He used way too long of an extension cord, which caused a ton of heat buildup.
3. He put a large load on the insufficiently sized extension cord when he ran his A/C. This caused the too small of a cord to heat up and start a fire.
The video below shows what happened because of these mistakes:
Use The Properly Sized Extension Cord Or This Will Happen
Using a smaller diameter cable and/or a too low rated amperage cable will cause more resistance for the electricity.
Also, the longer the wire, the greater the resistance.
Long cables and/or smaller cables cause a voltage drop as well as HEAT.
Both of these can cause a fire.
If you need to use an extension cord, use the shortest cord possible.
You should make sure it has the same amperage rating that your RV's shore power cord uses.
The diameter of the extension cord wire (aka, the wire gauge) should be the same as your shore power cord, or bigger.
This way there is little to no voltage drop when you are using high powered electronics such as your air conditioner or hairdryer.
Want to know which extension cords we recommend? Click the button below to read our reviews.
Difference Between an RV Power Cord and Extension Cord
An RV power cord is either:
- Hard-wired to the RV (so the cord is not removable)
- Is a removable cord that you have to attach it to your rig via a marine-style connector with a twist-lock.
The attachment typically goes like this:
You push the receptacle (female) end of the power cord onto the male 'plug' on your rig and give it a slight twist to engage the locking pin.
You then twist the circular locking ring down (much like you are screwing the lid on a jar).
This makes the power cord attach to your rig so it won't get knocked loose.
The other end of an RV power cord has traditional straight blades so that it can connect either to a power pedestal or an extension cord.
An RV extension cord has straight blades, NO curved blades, on both the male and female ends like in the photo below.
So to connect an RV extension cord you simply plug it to the straight blade end of your RV power cord (just like you would with an extension cord you use at home).
There is no twisting or other locking mechanism.
The tension of the straight blades on the male plug end going into the receptacle end of the adjoining cord is all that holds things together.
You use an extension cord together with your RV's power cord.
An extension cord alone cannot provide 120-volt power to your rig.
How To Plug Your RV Into Shore Power
So you get to your destination campground, you pull into your spot, get level and now it's time to plug in your 30 or 50-amp RV cord.
Don't be tempted to just plug in without testing the outlet first, no matter whether you have a 50-amp plug or a 30-amp plug.
There are plenty of campgrounds that don't have their wiring correct on any given pedestal.
You should first test the outlet using a polarity tester or a surge protector.
(Only use a surge protector IF that surge protector tells you if the outlet is wired properly or not.)
This is good insurance for keeping your electrical safe and sound.
An ill-wired outlet, or even too little power coming through the outlet, can lead to an RV electrical disaster.
Always, always check the power at the pedestal first!
Inspecting An RV Power Or Extension Cord
If you have a surge protector that plugs in at that pedestal, plug it in first, WITHOUT your shore power cord attached.
It doesn't matter whether it's a 50-amp RV cord or a 30-amp RV cord.
Once it reads ok, then you can plug in your shore power cord.
If you have a surge protector mounted inside your rig, make sure you have the kind that will 'test' the pedestal before allowing power to enter your rig.
Most interior-mounted surge protectors will do this, but make sure before you go plugging it into a pedestal.
If there is something wrong with the pedestal, the built-in surge protector will not allow power to get in and you should be alerted.
Should this happen, you should also alert the owner of the pedestal.
(Be aware, they may or may not listen to you. If they disagree, you better ask for a new spot or leave. It's not worth the risk of blowing up your entire rig.)
Checking Power Source Polarity, etc.
Do you just willy-nilly plug your RV shore power cord into a power outlet (pedestal) and hope that all will be right with it?
The majority of the time this is an OK way to go on with life, but when things go sideways with power, they go sideways in a big way!
You need to make sure that the power source you are using is wired correctly.
That is unless you like to start fires and fry expensive electrical systems on your RV.
There are two ways to check if the power source is wired properly.
If you are using a 30-amp power source, you can buy the Camco Power Defender circuit analyzer described below (not available in a 50-amp version).
Or you can be really smart and use an RV surge protector.
It will not only tell you if the outlet is wired correctly, but it will protect you from a lot of other potential electrical issues.
You are playing with fire (literally) if you don't check your power source before you plug your rig in.
It isn't unheard of for a power pedestal (or other power source outlet) to be wired incorrectly.
Such an event can cause major damage to your RV's electrical system.
CHECK before you plug in!
We recommend that you use a good RV surge protector (or more specifically, an electrical management system).
It will tell you if the outlet is safe to plug into, and it can protect you from voltage spikes, low and high voltage conditions, and more.
It's well worth the money to have this kind of electrical protection for your rig!
If you want to only have the bare minimum to allow you to check the outlet condition, you can use the Camco Power Defender circuit analyzer.
This is available for 30-amp receptacles only (you can use an RV surge protector if you have a 50-amp plug) and checks the condition of the ground, neutral and hot-wiring, as well as checks for correct polarity.
It also offers 1050 Joules of voltage surge protection.
Camco Power Defender Circuit Analyzer (30-amp)
Hot Skin Detection
There is an electrical danger caused by an incorrectly grounded RV that is known as 'hot skin' condition.
Hot skin is when your RV is electrified (any metal portion of the rig) due to a faulty electrical ground.
It can range from either a mild electrical tingling sensation to a massive shock that could potentially put you into cardiac arrest.
Hot skin is caused by an incorrectly wired power pedestal (shore power source), damaged RV power/extension cord, and/or wiring damage internal to the RV itself.
You only have to worry about this condition if you are plugged into a 120-volt power source (shore power or generator).
So if you are out boondocking and only have the 12-volt system humming along, you won't experience a hot skin condition.
You can protect your rig, and yourself, from a hot skin condition caused by an improperly wired power pedestal by using an RV surge protector.
This device will prevent power from reaching your RV (and causing hot skin) if there is a problem with the power source (improperly wired, etc).
To detect (or feel) a hot skin condition, you have to be standing on the ground and touching a metal part of the RV with the detection tool.
When you are standing on the ground, your body is forming the ground circuit for the RV that has the hot skin condition.
This is explained in the below video.
Explanation Of RV Hot Skin Condition And How To Detect
As Mike states in the above video, anyone who plugs their RV into shore power should have a voltage detection too.
Test your rig each time you plug-in (and before you touch your RV).
The Fluke VoltAlert tool that Mike recommends has an issue - it has a voltage sensitivity range of 90-1000 Volts AC.
The bottom end of the voltage range is above the 40 volts that Mike demonstrates in the video.
While it appears that the Fluke tool detects at this lower voltage (and Mike has stated on his blog that it will detect at 40 volts), we aren't comfortable recommending the Fluke device.
Instead, Klein Tools makes an equivalent tool that has a voltage range of 12 to 1000 volts AC. We like that!
You can purchase the Klein NCVT-3 via the below link.
It's quite affordable insurance against being electrocuted.
How To Plug Your RV Into A Portable Generator
I didn't know how to.
Then someone showed me how and it was embarrassingly easy!
Because I understand how intimidating it can be, I am going to explain to you how to do it as well.
First, know that most generators are not made specifically for RVs (unless they are specifically RV ready such as the Champion 75531i).
Therefore, you may find that there is no outlet on the generator that fits your RV power cord.
Once again, you simply need an adapter. (The Camp Addict portable generator page has a section on generator adapters that will walk you through what you need.)
Connecting Your Portable Generator To Your RV
1. If your RV is equipped with an inverter, turn it off.
2. Get the generator out, make sure it has sufficient gas and oil.
3. Turn the generator on, according to the instructions for your generator. Let it warm up for about a minute or according to the manufacturer's directions.
4. The generator's outlets are now 'live'.
5. Plug your shore power cord (with the appropriate adapter if necessary) into the generator.
6. Your rig should now have 120-volt power!
That's it! Easy peasy.
Generator Power Cords
A generator power cord isn't anything special.
You use your regular RV power cord to connect the generator to your rig.
The trick is how you plug your power cord into the generator.
Most 2000-watt generators have one (or more) 15-amp power outlets (just like what's in a house).
Some 3000 watts (and larger) generators come 'RV-ready' which means your 30-amp power cord can plug directly into it.
Most have a special receptacle that requires a special plug adapter.
So there is no special 30-amp generator cord or 50-amp generator cord.
Unless you are the lucky owner of an RV-ready generator (has a standard TT-30R 30-amp receptacle), you need to purchase the appropriate power cord adapter for use with your existing RV power cord.
See the portable generator page section on generator adapters to learn more.
There you have it.
It's complex, isn't it?
After you get to know your RV a little better you will more easily understand your RV power systems and how to use them.
Please be careful when using any type of power with your rig. 120-volts is nothing to mess with for sure.
Even your 12-volt system can give you a good zap if used incorrectly.
We hope you got some useful information out of this page regarding how to get power to your rig and regarding RV electricity in general.
Play it safe.
Use your head.
And if you have any questions, please read the comments below first.
Thank you for trusting Camp Addict!
Kelly Beasley is co-founder of Camp Addict and loves sharing her enthusiasm for the RVing lifestyle. As a full-time RVer since May 2015, Kelly's playful writing style helps make learning about the sometimes dull subject of RV products a bit more interesting.
Camp Addict co-founder Marshall Wendler brings his technical expertise to help explain RV products in an easy to understand fashion. Full-time RVing since April 2014, Marshall loves sharing his knowledge of the RV lifestyle.