March 26, 2017 @ 4:00 PM


If you know that you have 120 volts going into your RV, and you have 30 amp main service inside that RV, then if you multiply the 120 volts times the 30 amps, you get 3600 watts.  One might think there’s a proportionate link between differing amp levels when, in fact, that isn’t necessarily so. For example, 20-amp service requires 2,400 watts (20 amps times 120 watts), and 30-amp service needs 1-1/2 times as much power (3,600 watts, or 30 amps times 120 watts). For 50-amp service, however, the potential amount of power used – 12,000 watts, or 50 amps times 240 volts – represents more than three times as much possible demand as 30-amp service. Conversely, a 50-amp rig hooked up to a 30-amp outlet is only getting about one-third of the power that the rig may need to run a full complement of appliances.

So what does that mean to you?

Real Life Example

 Mr. and Mrs Smith, and the kids, hookup their travel trailer and head out for the weekend.  They had it plugged in at home and had all the electrical items running before they left.  They unplugged the RV and hit the road. The electric water heater was on, the air conditioner unit was running, the converter was charging the batteries, and the fridge was set to be on electric when plugged in.  Oh, and this is a 120 volt – 30 amp electrical system.

 So what happened when Mr. and Mrs. Smith get to their destination and plugged in their RV?  Remember, everything was left on!  Lets examine the load on the system:

  1. Air Conditioner at 20 amps x 120 volts = 2,400 watts
  2. Electric Water Heater at 12 amps x 120 volts = 1,440 watts
  3. Converter at 7 amps x 120 volts = 840 watts
  4. Dometic Fridge at 120 volts x 4 amps = 480 watts

for a Grand Total of 5,160 watt


All those appliances were still switched on and were calling for power, because the RV was hot inside, the hot water had cooled off, the fridge needed to keep cooling and was switching from propane, and the batteries needed charging.  After a few minutes of being plugged in, the Smith’s were sitting without AC, hot water, and ice cold beer because the breaker tripped. Perhaps it was the main breaker in the RV, or perhaps the breaker at the electrical pedestal.

They only had 3,600 watts available to use, at most!  And when an air condition first kicks on, it requires approximately another 500 watts.

 How could this have been avoided?

 Some RV Electrical No No’s!

  • The lesson from the example above is don’t unplug your RV without allowing your appliances to cycle off before shutting off the main power. Be sure to turn off your major amp drawing items and you will avoid tripping breakers when you get to your next destination.  Turn them back on when you need them, and not all at once, especially on a 30 amp RV!
  • Don’t plug your RV into a 15 amp outlet, using an adapter, and then try and run your Air conditioner unit.  You will ruin the ac and burn up your wiring. That may be okay to just run the converter to keep batteries charged, but that’s about it!
  • Don’t plug into an RV park electrical pedestal without checking the power source.  If you don’t know how to use a volt meter, either learn, or get an electrical management device.  These are designed to plug into the RV park’s electrical pedestal and detect any electrical issues before you plug in.
  • Don’t run all electrical appliances in your RV unless you know for sure what the power requirements are, based on a 30 or 50 amp RV electrical system.  That is 3,600 watts or 12,000 watts of total available power.

The rule of thumb is that you can run 1 heating or cooling device at a time on 30amp, so if your site doesn't have 50amp, switch your hot water heater and refrigerator to propane before you turn on your AC.