Introduction

Choosing the appropriate generator size for powering your camper or trailer is key to making sure you have adequate electrical capacity for running all your necessary devices and appliances. Generator output should match closely with the total power draw expected from the items you need to operate. Understanding your camper's electrical system amperage, along with your intended use, will dictate what generator size you require.

Evaluate Your Camper's Power Infrastructure

The electrical systems built into most campers and RVs will have specific power limits that must be considered when sizing an appropriate generator. Many smaller to mid-sized campers will come equipped with a 30 amp electrical hookup inlet, the standard receptacle that allows connecting to an external 30 amp, 120 volt AC power source. However, larger motorhomes may have 50 amp hookups, capable of drawing increased wattages for powering more substantial loads.

Inside the camper, regardless of 30 or 50 amp capacity, appliances and devices run on standard 120 volt current, like houses and buildings use. Two key dedicated circuits are pre-wired internally for the high-draw air conditioning unit and the microwave oven. So when determining generator needs, you must know your inlet plug configuration, what devices need simultaneous operation, and basic voltage requirements. This collective information will directly dictate the rated wattage of the power generator selected to safely power the complete electrical inventory inside your RV or trailer.

Calculate Total Electrical Power Demand

Making a comprehensive list of all the appliances, electronics, lighting, motors, and other items you aim to run while camped off-grid is crucial. This provides the basis for adding up the maximum rated wattage of each component to estimate the total anticipated power draw. Nameplates on devices list operating voltages and rated load, typically in watts or amps.

While individual small items may draw limited watts, simultaneously operating multiple systems can add up quickly. For example, concurrently running a 1500 watt air conditioner, 1200 watt microwave, and 1000 watt coffee maker would require at least a 3700 watt generator. Scaling upwards, motorhomes have the capacity for much higher loads like multiple ACs, large refrigerators, plus an array of outlets powering numerous gadgets. Carefully determining the realistically expected peak demand prevents issues like tripping breakers, damaging equipment, or inadequate runtimes from an undersized generator.

Consider Startup Power Spikes

When initially energized, certain devices briefly need double or more of their listed running wattage ratings to start internal motors and compressors. Microwaves, fridges, and pumps may have these momentary peak power draws. Most impactful are large AC units requiring potent jolts of electricity to ignite, demanding as much as 15,000 watts at onset. After starting, operational loads fall back down significantly. But if the generator can't provide these temporary highs, failure to start equipment is likely. Having a generator with some buffer capacity well over the maximum expected running watt total allows for most surge demands. So while a 5000-watt unit could maintain a 1500-watt AC alone, 7500+ watts enables successful turn-on of that AC along with concurrently running other devices.

Sizing Suggestions for Common Camper Setups

• For basic small trailers under 20 feet, a 2000-3000 watt portable inverter generator sufficiently powers essential items like lighting, water pumping, and battery charging.
• Older 30 amp Class C motorhomes around 25 feet predominantly utilize one roof AC unit. A 4000-5000 watt conventional generator operates this adequately while also allowing a microwave, some lights, and appliance charging.
• Larger fifth wheel and travel trailers between 30-40 feet with 50 amp service can run dual ACs, large washer/dryers, multiple televisions, and other amenities demanding 5000+ continuous watts, suggesting a 7500-10000 watt generator size including surge capacity.
• Bigger custom motorcoaches over 40 feet may have 15,000 watts or more potential total load. These luxury homes on wheels require 10,000+ watt diesel generators regularly put under high demand.

Make sure to account for everything needing simultaneous power, including potential future additions. Safely meet demands without overloading either the generator or motorhome. An electrician can always measure precise energy use, too, if uncertain. Investing in adequate wattage upfront saves money and protects appliances while providing enough power.

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