RV Generators Guide

Generators are one of the most debated components in RV electrical conversations – and one of the most frequently misunderstood. Some RV owners buy a generator before they need one and run it constantly out of habit. Others dismiss generators entirely after investing in solar, then get caught short during three consecutive overcast days. Neither approach reflects how generators actually fit into a well-designed RV power system.

The most common mistakes with RV generators follow a predictable pattern: buying more wattage than the actual load requires, assuming solar makes a generator unnecessary, and treating a generator as a primary power source rather than a backup and supplement. Each of these errors costs money, creates unnecessary noise, and reflects a misunderstanding of what generators are actually for.

This guide explains how generators work, what types exist, when one is genuinely needed, how to size one correctly, and how to use one safely. If you’re already ready to shop, see our picks for the best RV generators. For context on how a generator fits into the full RV electrical system, see the Complete RV Electrical Guide.

How RV Generators Actually Work

A generator converts mechanical energy – from a combustion engine running on gasoline, propane, or diesel – into electrical energy. The output is 120-volt AC power, the same type that comes from a shore power pedestal at a campground. That AC power can be used in two ways in an RV context.

First, it can power AC appliances directly – running an air conditioner, microwave, or power tools while the generator is on. The generator acts as a temporary substitute for shore power.

Second, it can charge the battery bank through the RV’s converter or inverter/charger. This is the more strategically useful function for most off-grid setups. Rather than running the generator continuously, you run it for two to three hours to bring the battery bank from a low state of charge back up to a functional level, then shut it off and run on battery power again.

The key distinction between generator power and battery power is availability. A generator produces power only while it is running. A battery delivers power on demand, silently, at any hour. A well-designed off-grid system uses the generator to serve the battery, not to replace it.

Types of RV Generators

Portable Inverter Generators

Portable inverter generators are the most practical choice for the majority of RV owners who need a generator. They produce clean, stable AC power through an inverter circuit, which makes them safe to use with sensitive electronics including laptops, phones, and modern appliances. They are significantly quieter than conventional generators – typically 50-60 dB at full load, comparable to a normal conversation at a distance. Many run at 51-55 dB at quarter load, which is quiet enough to use at many campgrounds during daytime hours.

They are also fuel-efficient. Inverter generators adjust engine speed to match the actual load rather than running at a fixed RPM regardless of demand. At partial load – which is typical when charging batteries or running modest appliances – they consume significantly less fuel than a conventional generator of equivalent rated wattage.

The trade-offs: they cost more than conventional generators of similar rated wattage, and the most practical models for RV use top out at around 2,000-3,500 watts. Two inverter generators can be parallel-connected to double output for higher-demand situations, which provides flexibility without committing to a single large unit.

Built-In (Onboard) Generators

Many larger Class A and Class C motorhomes come with an onboard generator installed from the factory – typically an Onan unit fueled from the same tank as the vehicle’s engine. Built-in generators offer significant convenience: they start from a switch inside the cab, run quietly in an enclosed compartment, and do not require any setup or stowage.

The limitations are cost and flexibility. Factory onboard generators are expensive to repair or replace, run on a fixed fuel type, and cannot be transferred to a different rig. For owners of large motorhomes who camp frequently in locations without hookups, the convenience is worth the trade-off. For fifth wheel and travel trailer owners, a portable inverter generator is the practical alternative.

Conventional Generators

Conventional generators produce AC power at a fixed engine speed (typically 3,600 RPM) regardless of load. They are loud – typically 70-80 dB or more – less fuel-efficient at partial loads, and produce dirtier power that is not suitable for sensitive electronics without a surge protector or additional filtering. They are cheaper per watt of output than inverter generators, which makes them common in construction and industrial contexts.

For RV use, conventional generators are rarely the right choice. The noise level alone disqualifies them from most campsite use. The fuel inefficiency at partial loads – which is the typical use case for RV battery charging – adds operating cost that erodes the upfront savings. Unless the sole purpose is running a large air conditioner for extended periods in a remote location where noise is not a concern, an inverter generator is a better fit for RV applications.

Generator vs. Solar: Understanding the Real Relationship

Solar and generators are often framed as competing solutions. They are not. They serve different functions in an off-grid power system, and understanding those functions prevents both over-reliance on one and dismissal of the other.

Solar is continuous and passive. On a clear day, panels produce power from sunrise to sunset without any intervention, fuel cost, or noise. That production charges the battery during the day so it is available at night. Solar is well-suited to handling routine daily power needs in favorable conditions.

A generator is on-demand and reliable regardless of weather. It produces power whenever it is running, independent of sunlight, clouds, or season. It is well-suited to two specific situations: recovering a depleted battery bank quickly, and powering high-draw appliances that solar and battery alone cannot support.

Solar handles daily energy needs under normal conditions. A generator handles recovery after extended low-production periods and powers loads that exceed what the battery and solar system can realistically supply.

The practical implication: a solar system designed for typical sunny conditions will fall short during extended cloudy weather. A generator bridges that gap – run for two to three hours to recharge the battery bank, then shut off. This is far more efficient and less disruptive than running a generator continuously as a primary power source.

For a detailed explanation of how solar and battery systems interact, see the RV Solar Guide.

When You Actually Need a Generator

Not every RV owner needs a generator. The decision depends on how and where you camp, what appliances you use, and how your existing system is configured.

Conversely, a generator is probably unnecessary if you camp primarily at sites with electrical hookups, rarely go more than one night without shore power access, or have a battery bank large enough to comfortably handle one or two low-production days before your next hookup.

Generator Sizing

Starting Watts vs. Running Watts

Every generator is rated for two wattage figures: running (or continuous) watts and peak (or starting) watts. Running watts is the sustained output the generator can maintain. Peak watts is a brief surge capacity available for a few seconds when a motor-driven appliance starts – air conditioners, refrigerators, and pumps all draw 2-3 times their running wattage on startup.

Size a generator based on the running watts of the largest load you plan to run, plus a margin for any simultaneous loads. Then verify that the peak wattage is sufficient to start the highest-draw motor in the system. A generator that can sustain a load but cannot start it is not adequately sized.

Typical RV Appliance Loads

Practical Sizing by RV Type

Small RV, van, or trailer without AC: A 2,000W inverter generator is typically sufficient. It handles battery charging, microwave use, and most small appliances without excess capacity.

Mid-size trailer or Class C with one AC unit: A 3,000-3,500W inverter generator handles a single AC unit plus simultaneous battery charging or other modest loads. This is the most versatile size for most RV owners who occasionally need to run cooling.

Large Class A or fifth wheel with dual AC: 4,000W or more is required to run two air conditioners simultaneously. Many owners in this category rely on onboard generators sized for this purpose from the factory.

Fuel Types

Gasoline

Gasoline is the most common fuel for portable RV generators. It is widely available, produces the highest power output per unit of fuel, and most inverter generator models run on gasoline. The limitations: gasoline degrades over time in storage (fuel stabilizer is required for long storage periods), and it must be carried in approved containers with the associated safety and space requirements.

Propane

Propane burns cleaner than gasoline, stores indefinitely without degrading, and can draw from the same propane system that feeds an RV’s stove and furnace. The trade-offs: propane produces roughly 10-15% less power output than gasoline in the same generator, propane-only generators are less common and limit equipment options, and at high altitude propane performance drops more noticeably than gasoline.

Dual-Fuel

Dual-fuel generators run on either gasoline or propane, switchable via a valve. They offer flexibility – gasoline for maximum output when needed, propane when fuel storage or shelf life is a priority. For RV owners who camp in varied conditions and want operational flexibility, dual-fuel is worth the modest premium over single-fuel models. Most dual-fuel generators produce slightly less power on propane than on gasoline, consistent with the chemistry difference.

Noise and Real-World Use

Generator noise is measured in decibels (dB) at a specified distance – typically 23 feet (7 meters). A 50-dB rating at 23 feet is approximately as loud as a normal conversation. A 65-dB rating is closer to heavy traffic. The difference between 50 dB and 65 dB is not just 15 units – decibels are logarithmic, meaning 65 dB is roughly 30 times louder than 50 dB in perceived intensity.

Most campgrounds that permit generators restrict use to daytime hours – typically 8am to 8pm or 9am to 9pm – and some prohibit them entirely. National Park campgrounds frequently ban generators. State park policies vary by site. Check the specific campground rules before assuming generator use is permitted.

Placement matters. Pointing the exhaust away from neighboring campsites reduces perceived noise at the source. Running a generator at the end of the rig furthest from the campsite of nearest neighbors also helps. Some RV owners build simple sound-deflecting barriers from plywood for particularly sensitive situations, though this requires care to maintain adequate ventilation for the generator.

Load affects noise. Inverter generators are notably quieter at partial load than at full rated output. Running a 2,000W generator to charge batteries (a 400-700W load) keeps the engine at low throttle and meaningfully reduces noise compared to running it hard with the AC on.

Common RV Generator Mistakes

Oversizing the generator. A generator rated far above the actual load runs inefficiently and costs more upfront. A 2,000W inverter generator handles battery charging and typical small appliance use effectively. Buying 4,000W for those tasks wastes money and produces unnecessary noise.

Running the generator unnecessarily. Some RV owners run generators for comfort rather than need – keeping the AC on through the afternoon at a site where a shaded spot and a 12V fan would suffice, or running it overnight out of habit rather than battery necessity. Fuel cost and campsite etiquette both argue for using the generator purposefully rather than continuously.

Ignoring campsite restrictions. Arriving at a campground and discovering generator use is prohibited – or restricted to hours that do not fit the planned schedule – is a common and avoidable problem. Check policies in advance, particularly for National Forest, BLM, and National Park sites.

Poor fuel management. Gasoline left in a generator’s carburetor for extended periods gums up the fuel system. Running the generator dry before storage, or using fuel stabilizer in stored fuel, prevents the most common maintenance problem with portable generators. Ethanol-blended gasoline degrades faster than ethanol-free fuel – where available, ethanol-free gasoline extends both fuel shelf life and carburetor longevity.

Treating a generator as a substitute for system planning. A generator does not compensate for an undersized battery bank or a solar array that cannot meet daily consumption. It supplements a system that is otherwise functional. Buying a generator to paper over a fundamental sizing problem leads to running it more often and more continuously than necessary.

Generator Safety

Carbon monoxide is the primary risk. A running generator produces carbon monoxide – an odorless, colorless gas that is lethal at sufficient concentration. Every year, people are killed by generator carbon monoxide in camping contexts, typically from running a generator too close to a vent, window, or door, or inside an enclosed space.

Never run a generator inside the RV, in an attached or closed compartment, in a garage, or in any partially enclosed space. Run it outdoors with the exhaust directed away from the RV’s windows, vents, and doors. Keep a minimum of 10-20 feet between the generator exhaust and any opening in the RV. A battery-powered carbon monoxide detector inside the RV is a basic safety measure that should be treated as mandatory, not optional.

Cord management. Extension cords between a portable generator and the RV must be rated for outdoor use and for the amperage of the load. An undersized extension cord creates resistance heat and is a fire risk. Use a cord rated for at least 30 amps for any connection to the RV’s shore power inlet, and keep cord runs as short as practical.

Wet conditions. Generators should not be operated in rain or standing water without a proper canopy or cover that allows adequate airflow. Running a generator in wet conditions without protection creates both electrical safety risks and accelerated corrosion of components.

Fuel storage. Store gasoline in approved containers away from the living space of the RV and away from heat sources. Never refuel a generator while it is running or immediately after shutting it off – the engine and exhaust remain hot and can ignite fuel vapors.

Decision Summary

For a complete picture of how a generator fits into your RV electrical system alongside batteries and solar, see the Complete RV Electrical Guide. For guidance on the battery bank that a generator will charge, see the RV Batteries Guide. For how solar and generators work together in an off-grid setup, see the RV Solar Guide. Ready to choose a unit? See our tested recommendations in the best RV generators guide.