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Watts to amps, and what your hook-up can run

Watts are the honest currency of power: volts times amps. Below you can convert either way, see the total watts your campsite service can supply, and check your appliances against it. Every box says where its number comes from.

The answer updates as you type. Nothing is sent anywhere.

Convert either way

RV side of things: outlets and most shore power are 120 V, a 50-amp cord carries two 120 V legs, and the house batteries are 12 V.
How to get it: printed on the appliance label, the box, or the manual. A space heater is usually 1,500.
How to get it: printed beside the watts on the same label, or on the plug. A household outlet is 15 or 20 amps, and the breaker that feeds it says which.

Your campsite service

How to get it: read the plug on your cord. A 30-amp plug has three prongs in a round body, a 50-amp has four prongs in a larger body. The park's pedestal says the same thing. A 50-amp cord is really two 50-amp legs, which is why it carries 12,000 watts and not 6,000.

Check the appliances you expect to run at the same time. The meter shows whether they fit inside your service.

The one formula, and the two numbers people mix up

Watts equal volts times amps. That is the whole conversion: 1,500 watts at 120 volts is 12.5 amps, and 12.5 amps at 120 volts is 1,500 watts. The number people mix up is the 50-amp service, which is 12,000 watts rather than 6,000 because a 50-amp shore cord is rated at 240 volts across two separate 50-amp legs: each leg supplies 6,000 watts, and 6,000 plus 6,000 is 12,000. Cummins states both figures plainly, and so does our generator sizing guide, which uses the same numbers for the same reason.

The other trap is the dogbone adapter. Plugging a 50-amp cord into a 30-amp pedestal with an adapter does not give you more power: you still have 3,600 watts, and the pedestal breaker enforces it. The adapter only changes the plug shape.

Starting surge, the hidden number

Air conditioners and refrigerators draw two to three times their running watts for the seconds after the compressor starts. A 13,500 BTU air conditioner that runs at 1,250 watts can ask for 2,500 or more in that moment, which is why two air conditioners on one 30-amp service is a gamble even though the running watts appear to fit, and why the appliance rows below carry a starting figure where the source publishes one.

Where to go next

The generator sizing guide uses the same watts math to pick a generator that can start your air conditioner. The battery runtime calculator answers the off-hookup version of this question: how long the house batteries last.

Sources