What Size Wire For 30 Amp And 50 Amp RV Service?

As RVs develop, they are becoming more a home-from-home than ever before. Most modern RVs have all the conveniences you find in the average house, and these comforts make camping in an RV a wonderful experience.

It is essential that you correctly size the wire which you use to connect your RV to the main power supply. For a 30-amp system, you need a 7-gauge wire with a diameter of 0.1443 inches, while for a 50-amp system, you will need a 4-gauge wire with a diameter of 0.2043 inches.

Just like the size of a pipe or hose determines the volume of water you can send, the cable used to connect the RV to the RV site’s services determines how many amps can be drawn by the circuit.

Why Does RV Wire Size Matter For An RV Service?

Wires are rated for the voltages and amps that the wire can carry.

A larger diameter wire can carry more current than a smaller one. The higher the circuit’s amperage rating, the larger the electrical cables you need to avoid excess heat that can melt wires and cause fires.

Thus, using the correct wire size depending on the Voltage and amperage is crucial to avoid such accidents.

If you’ve ever gone to the shops looking for electrical wire, you will know that there are a mind-bending number of wire types and sizes which you can choose from. Each wire type is intended for a specific application.

When looking for the correct wire for your RV’s 30-amp or 50-amp system, you need to make the right choices.

Knowing the correct wire size or gauge is key to making the right choice with any of these wire types.

A wire is sized by the American Wire Gauge (AWG) system.

The diameter of the wire equals the gauge assigned by the AWG system.

Strangely as the gauge of the wire increases, the diameter of the wire reduces. The smaller the gauge, the bigger the diameter is, and the greater the wires’ ability to transport bigger amperages.

Standard American Wire gauges are.

  1. 14 gauge -5.9 amps
  2. 12 gauge -9.3 amps
  3. 10 gauge -15 amps
  4. 8 gauge -24 amps

To ensure that you have a wire capable of managing the flow of electricity, consider the following variables.

The Material Which The Wire Cable Is Made From

Different conducting materials used in wires have different resistances, and therefore the size of the wire used will depend on this factor.

Aluminum wires have less conductivity (higher resistance) than copper wires. To conduct 30 and 50 amps of current over 50 feet (15 meters), you need the following wire sizes.

Conductive materialWire size to conduct 30 ampsWire size to run 50 amps
Aluminum0.1819 inches0.2576 inches
Copper0.1443 inches0.2043 inches

Distance Needed To Be Covered For An RV Service

The length of the cable has a significant impact on the diameter wire used to connect your RV to the RV site’s main power supply.

The regular length of an RV cable is 50 feet (15 meters). At this distance, the resistance is insignificant, and the wire sizes listed in the above table can apply.

If the distance is half the distances shown above, you can reduce the wire size because less resistance will be present in the circuit (more about this later.)

You can reduce the wire diameter size by 20% if the distance is halved.

The same applies to longer runs of wire, and if you double the length to 100 feet (30 meters), you will need to increase the wire size by 25%.

>>Check out our article on: Best RV Power Cords & Adapters

What Do We Mean By Amps?

The four main electricity measurements relevant are Voltage, Amps, Watts, and Ohms.

When your energy bill arrives, it shows you used a certain number of kilowatt-hours, but when you buy bulbs, they are measured in watts, and then you have 9-volt batteries and vacuum cleaners that have 15-amps of vacuum power. What are the purposes of so many measures of electricity?

Like in a plumbing system, four things must happen to make electrons flow in an electrical circuit.

The following table summarises each of these three measures.

QuantitySymbolUnit of MeasurementUnit Abbreviation
CurrentIAmperes (Amp)A

It is possible to work out virtually any aspect of an electrical circuit, whether the current draw and the size trip switches needed, the size wires required, the power produced by the system or the available potential energy.

What Is Voltage (V)?

Voltage is the energy per unit charge available to move current flow from the negative terminal, the device to be powered, and the positive terminal.

What Are Amps (A)?

Once the current (water) moves, you need to measure how much water flows. This measurement is called amps and is the number of electrons moving past a specific point in the circuit; if too many amps pass through, the circuit trips.

A current of one ampere equals one coulomb of electrical current going past a given point per second. One coulomb equals 6.24 × 1018 electrons.

What Are Watts (W)?

So, we opened the switch (tap), measured the voltage difference between the negative and positive terminals, and measured the number of electrons in the circuit (amps). The resultant pressure is called watts.

Watts is the measure of power that determines how much work can be performed in each amount of time.

What Are Ohms (Ω)?

If the pipe is obstructed, or perhaps it has rusted, the water will be subjected to some “push back” or resistance. Resistance is measured as the Ohm.

The most common resistance used in a circuit is the light bulb. The light bulb introduces enough resistance in an electrical circuit to heat the filament inside, causing light to be emitted.

Do These Help Size Wire For 30 And  50 Amp Service?

Choosing the thickness of wire needed to supply different ampere values to an RV is essential.

What is the difference between 50-amp RV receptacles and 30-amp RV receptacles?

50amp plugs are four-hole plugs that include

30amp plugs are three-hole plugs that include

American Wire Gauge (AWG)

The higher the wire gauge, the narrower the wire. A 10 gauge wire has a diameter of 2.588mm (0.1 inches), whereas a wire gauge of 20 has a diameter of 0.812 mm (0.03 inches).

The lower the wire gauge number, the higher the number of amps conducted through the circuit.

A wire gauge of seven can handle 30 amps, whereas a wire gauge of 15 can only handle 4.7 amps.

The next thing to consider is the resistance of each wire gauge. It is measured as ohms (Ω) per one-foot length of wire. As the wire gauge increases in value, so does the resistance.

A ten-gauge wire has a resistance of 1 milliohm (1m Ω) per 1000 feet, whereas a 20-gauge wire has a resistance of 10 ohms (1m Ω) per 1000 feet.

The official American Wire Gauge table is provided below.

AWGDiameter [inches]Diameter [mm]Resistance [Ohms / 1000 ft]Max Current [Amperes]Area [mm2] 
0000 (4/0)0.4611.6840.049302107  
000 (3/0)0.409610.403840.061823985  
00 (2/0)0.36489.265920.077919067.4  
0 (1/0)0.32498.252460.098315053.5  

As you can see, for a system drawing 30 amps of current, a 7-gauge wire is needed, while a 50 amp system requires a 4 gauge wire.

For every wire gauge increase of 10 units, the ohms increase by a factor of ten, for example.

Different wire types have different levels of resistance. Copper is a better conductor of electricity than aluminum or Copper Clad aluminum wires.

Longer runs may require an upgrade of the wire size as the length increases, the resistance increases, and the current decreases.

The maximum distance you can run and 8-gauge or 4-gauge wire at 30 amps or 50 amps is 18 feet.

Things To Consider When Selecting Wire For An RV Service

If you have plugged a piece of equipment into a circuit with a higher amp rating than the circuit is designed for, usually, the fuses or trip switch will activate and open the electrical circuit.

If the trip switch is faulty, there is the potential that a device that draws more current than allowed, and if the fuse or circuit breaker doesn’t activate, the wires which make up the circuit could heat up to the point where they melt the insulation around them and ignite the surrounding materials.

To ensure that this never happens, it is essential that

The following are the amps used by common appliances and the gauge wire they need to run safely.

DeviceRated AmpacityWire Gauge
Low-voltage lighting and lamp cords10 amps11-gauge
Light fixtures, lamps, lighting circuits15 amps10-gauge
RV fridge,  120-volt air conditioners, etc20 amps8-gauge
Electric clothes dryers, 240-volt window air conditioners, electric water heaters30 amps7-gauge
Electric furnaces, large electric heaters60 amps4-gauge

Remember that amperes are accumulative. The drawn amps add up if you have several machines running on a circuit. If the total amps of all the items exceed the amperes of the electrical circuit, the fuses will trip.

The difference between an RV with a four-wire 50-amp RV Service and a three-wire 30-amp service is that the 50-amp service is two 120-volt circuits fed to two different sides of the RV switchboard.

It would seem logical that the two circuits would combine, and a 240-volt capacity is enabled.

The two circuits don’t join inside the RV, so each is still restricted to 120Volt power.

The benefit of having a 50-amp circuit is that the watts (power) produced by the system are increased significantly.

A 50amp system can run higher wattage draw units than a 30 amp system.


The amps that an RV draws determine the type of electrical equipment used in the RV. The higher the number of amps an RV uses, the greater the wire’s diameter, connecting the RV to the services.

If you doubt the wire size you should use in your 30-watt or 50-watt RV, seek professional advice from a qualified person.

Good luck, and happy camping!

Check out our article on: Best RV Power Cords & Adapters

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