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How Long Can You Run an Onan 5500 Generator?

How Long Can You Run an Onan 5500 Generator?

Whether your generator is portable or stationary, it requires fuel like gasoline, propane, natural gas, or diesel to operate and we all know; the initial cost is just the tip of the iceberg. That’s why the fuel efficiency matters so much, doesn’t it? As an avid hiker, I recently purchased the Onan 5500 Generator through word of mouth.

Now a common question I’ve observed by owners of Onan 5500 Generator over several groups and forums is regarding the durability and span of a generator: How long can my generator run? I did my research and tested out certain variables to find out the answer to ‘How Long Can You Run an Onan 5500 Generator?’.

The Basics of an Onan 5500 Generator

The Onan 5500 generator is in massive demand in recreational vehicles RVs, as well as for general use.  It is manufactured by Cummins Inc. and is part of the Onan QG series of generators. Onan 5500 generator offers a quiet operation with minimal vibration. The enclosed muffler makes it easily installable as it bears self-diagnosing functions.

The generator is powered by a Cummin’s Onan OHV engine, with an adjustable mechanical governor accessible from the service side. The generator is able to deliver an estimated 5500 watts and operates on gasoline, 10% ethanol or less —weighing 288 pounds and measuring 33.6 inches long, 22.2 inches wide, and 16.7 inches high (dry). The generator offers sound attenuated enclosure housing coupled with a quiet operating sound rating of 69 dBA at only 10 ft. The Onan 5500 generator is a reliable and effective power supply specifically designed for use in RVs and any other application requiring portable power.

The Fuel Consumption

The fuel consumption of an Onan 5500 generator depends on the load and fuel type. Here are some estimates for each fuel:

  • Gasoline: On average, the Onan 5500 generator uses 0.5 gallons of fuel per hour under moderate loads. However, high energy demands can drive that fuel usage up to a gallon per hour, while light usage can bring it down to approximately 0.2 gallons per hour.
  • Propane: Onan’s 5500 generator model uses 0.8 gallons of propane an hour under a moderate load (or ‘half-load’). However, placing the generator under a full load will burn up 1.1 gallons of propane an hour instead.
  • Diesel: The Onan 5500 generator doesn’t commonly use diesel so it’s difficult to calculate the accurate fuel consumption but as an estimate, the fuel capacity of an Onan 5500 generator is 6.6 gallons of diesel. The fuel consumption rate of the generator varies depending on the load level, and it ranges from 0.25 gallons per hour at no load to 0.66 gallons per hour at full load.

Regarding the load levels, their average usage was around 18-32 amps, depending on if both AC units were running, or if the microwave was being used so the generator would allow you to draw 45 amps.

Pros and Cons of Different Fuel Sources: Gasoline, Propane, and Diesel

As the owner of multiple generators I’ve observed some common advantages and disadvantages of using various fuel sources, so here are some of the fuel sources widely used and the ones mentioned above:


  • Pros: Widely available and often less expensive than other fuels, depending on location
  • Cons: Highly flammable and produces larger amounts of emissions compared to propane


  • Pros: Ideal for remote sites
  • Cons: Highly flammable


  • Pros: More fuel-efficient than gasoline
  • Cons: Produces more emissions than propane

If you want to calculate the estimated running time of the Onan 5500 generator based on the fuel consumption and capacity, you can use the given formula:

Estimated running time = Fuel capacity / Fuel consumption rate

Let’s say you have a full tank of gasoline with a capacity of 7 gallons and the generator uses 0.5 gallons of fuel per hour under moderate loads, the estimated running time would be:

-Estimated running time = 7 gallons / 0.5 gallons per hour = 14 hours

Similarly, if you have a full tank of propane with a capacity of 20 gallons and the generator uses 0.8 gallons of propane per hour under a moderate load, the estimated running time would be:

-Estimated running time = 20 gallons / 0.8 gallons per hour = 25 hours

The fuel consumption rate may change based on load level and other factors and may not be precise as per the running time.

Load and Power Demand

The power output of the Onan 5500 generator is about 5500 watts and draws at a maximum power of up to 45 amps. In normal conditions, this generator consumes approximately 20-36 amps. However, it depends upon the scenario if both AC units were running, or if the microwave was being used.

Fuel consumption depends upon loads and therefore a half-load generator consumes about 0.6 gallons of fuel per hour, whereas a full-load mode generator would consume around 0.9 gallons of fuel per hour.

This generator’s power output indicates it can handle appliances and devices up to a total of 5500 watts. When you’re connecting devices to your Onan 5500, check their product labels or literature for their rated power.

Remember, the rated power is usually about 90% of the maximum power a device can handle. For example, if a device has a rated power of 1000 watts, its maximum power might be around 1111 watts.

Your generator’s consumption of 20-36 amps under normal conditions aligns with this.  It’s higher when both AC units are running or when using high-power appliances like microwaves. Regarding fuel consumption, the Onan 5500’s efficiency is evident.

At half-load, it consumes about 0.6 gallons per hour, while at full-load, it’s around 0.9 gallons per hour.  This consumption rate is crucial for planning fuel needs based on your expected load.  Always ensure your total power requirement is within the 5500 watts capacity of your generator for optimal performance and safety.

Reduce Load and Power Demand of Onan 5500 Generator

  1. Avoid overloading the generator: If you overload the generator, you may be risking it to malfunction or even break down, so to avoid this, connect only the appliances that fall under the generator’s capacity. You can also change the start times of appliances to reduce the load on the generator.
  2. Exercise the generator regularly: By doing this, you can keep it in good working order and prevent fuel varnishing that may affect the performance if the generator is stored for an extended span. The best practice is to run your generator at least once a month, under load. So you won’t be just firing it up but turning on enough high-draw items to ramp up the power.
  3. Keep the generator clean and inspect it regularly for damage: Your generator will provide peak performance don’t forget to use Cummins oil as well as service/maintenance, so as to make sure your generator lasts longer.
  4. Adjust the governor and throttle stop: Adjusting the governor and throttle stop can help regulate the speed of the generator and prevent overloading. However, it is recommended to do this with a frequency and volt meter. If you are not familiar with this process, it is best to consult a professional.

Monitoring the Load and Power Demand

Here’s how you can monitor the load and power demand of the Onan 5500 generator using the control panel, gauges, and indicators:

  1. Control panel: Important information concerning the status of the generator, the fuels remaining on the generator, and the resulting voltage output is displayed in the control panel of the unit. By checking the voltage output and frequency, you will be able to see how the generator is performing using the control panel. It can be a sign of an overload or underload situation if the voltage output exceeds or falls beneath the normal limits.
  • Gauges: Some of the modern generators have gauges for output voltage, frequency, and ampere reading. The instruments allow you to measure load and power requirements for the generator. High amperage may signify an overload situation
  • Indicators: The generator may have some indicators like the “running” indicator or the “off” indicator. These indications will help you gauge the load and power generated by the generator. This might occur if a generator runs but does not supply any electrical energy. This could be because of the occurrence of an overload condition.

You can observe the load on the Onan 7500 generator and the amount of power it consumes with the help of the panel, gauges, and indicators, to ensure it operates under the limit in order not to cause its failure.

Maintenance and Service

I’ve always believed that maintenance is the most important part of making basically any electrical device last. Maintenance and service are a no-compromise zone for the Onan 5500 generator’s running time. Regular maintenance ensures the generator runs efficiently and lasts longer.

Skipping maintenance can lead to breakdowns and reduced lifespan and if you’re skeptical about how to really keep your generator durable, follow the manufacturer’s instructions, change oil and filters, clean spark plugs and air filters, and most importantly…check the battery and wiring.

Here’s a basic maintenance schedule:

– Pre-start: Check oil levels, inspect for leaks, and ensure clear exhaust and intake areas.

– Daily: Inspect for loose parts, and leaks, and check oil and coolant levels.

– Weekly: Clean air filter, check battery terminals, and inspect wiring.

– Monthly: Change oil and filter, inspect spark plugs, and test battery.

– Annually: Replace spark plugs, check fuel lines, and perform a thorough inspection.

Troubleshooting common problems:

– Low oil pressure: Check oil level and quality. Replace if necessary.

– High temperature: Ensure proper ventilation, and check coolant levels, and radiator.

– Low voltage: Inspect battery, wiring, and connections.

– High frequency: Adjust governor settings and check engine speed.

Environmental Conditions and Altitude Needed For Onan 5500 Generator

The Onan 5500 is highly dependent on environmental conditions as well as altitude. These include temperature, humidity, and air quality. High temperatures can also hamper efficiency and raise chances of overheating of the energy source, so you must keep track of the generator especially during the summer season, when there may be a need to adjust settings so as not to cause any damage. The generator shall be monitored and probably adjusted since severe breakdowns are possible when conditions aren’t optimal.

Condensation within a generator can happen when the generator is stored in a damp location or when there are temperature fluctuations. This fluctuation may cause a rise in humidity levels that can lead to short circuits and corrosion. Please ensure that the generator has no contact with water, and is kept in a well-ventilated place.

Let’s talk about the air quality now. If you live in dusty arid places, the generator filters may become inefficient and require regular cleaning or full changes for the most. Not only this, but the altitude can impact the generator’s health too.

The air thins as one moves into higher altitudes so less oxygen will be provided for burning, thus causing low energy generation and excessive use of fuel. I suggest using a high-altitude kit or derating factor as compensation so your generator can function like a boss in thin-air conditions.

You can understand by now that the Onan 5500 generator functions differently in versatile environments.

Protect the generator against direct sunlight, rain, coldness, snow, and dust. This includes harmful agents that might damage the generator’s constituents. Make sure that the place has enough air circulation to avoid overheating and ensure good exhaust removal. Keep a clear area around the generator for fire safety and optimal performance.

Frequently Asked Questions

How many hours is an Onan 5500 good for?

There’s no rule of thumb for the span it can last for as it depends on how well it is maintained and serviced. But from what I have observed, it can run up to 2000 hours if properly maintained and serviced.

How many hours can you put on an Onan generator?

The Onan 5500 generator, like most generators, doesn’t have a strict hourly limit for daily use but continuous operation can last up to 8-10 hours.

Can you run an RV generator 24/7?

No, it’s recommended to run an RV generator 24/7 as it can cause overheating and damage to the generator.

How long should I let my RV generator run?

2 hours under full load for maintenance. If you’re using it for power, run as needed but avoid continuous operation for over 12 hours. Regular breaks help prevent overheating and extend its life.