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Old 05-08-2018, 09:42 PM   #1
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Generator Fuel Consumption Data

Below is fuel consumption data from generator manufacturers that may be of interest for RV applications. I rounded off to 2 significant digits since most of the information given is no more accurate than that — like size of fuel tank.

To make it easier to compare different sizes to each other, I’m expressing data in gallons of fuel per energy produced, or gallons per kilowatt-hour. And yes, I know a gallon of Diesel has more energy than a gallon of gasoline, but we buy both by the gallon, and store in fuel tanks and containers measured in gallons.

Note that Onan data are listed at 100% and 50% generator load, whereas inverter generators are typically listed at 100% and 25% of rated capacity.

Onan Generators:

2800 Watt RV Gasoline

.14 gallons / kWh at 100%

.21 gallons / kWh at 50%


4000 Watt RV Gasoline

.18 gallons / kWh at 100%

.25 gallons / kWh at 50%


3200 Watt RV Diesel

.12 gallons / kWh at 100%

.19 gallons / kWh at 50%


6000 Watt RV Inverter Diesel

.12 gallons / kWh at 100%

.13 gallons / kWh at 50%



Honda Inverter Generators:

900/1000 Watt Portable

.21 gallons / kWh at 100%

.38 gallons / kWh at 25%


1800/2200 Watt Portable (New)

.16 gallons / kWh at 100%

.26 gallons / kWh at 25%


2500/2800 Watt Portable

.16 gallons / kWh at 100%

.28 gallons / kWh at 25%


2800/3000 Watt Portable

.17 gallons / kWh at 100%

.24 gallons / kWh at 25%



Champion Inverter Generators:

2800/3100 Watt Portable

?? gallons / kWh at 100%

.29 gallons / kWh at 25%


3100/3400 Watt Portable

?? gallons / kWh at 100%

.28 gallons / kWh at 25%
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Old 05-08-2018, 09:56 PM   #2
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Greek. This makes no sense to me, but...at my age not much does anymore. My manual says .5 GPH at 50% load and .8-1.0 GPH at near 100% load. What's the difference here? Who goes by kWh?
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Old 05-08-2018, 10:31 PM   #3
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Originally Posted by The Gritz Carlton View Post
Greek. This makes no sense to me, but...at my age not much does anymore. My manual says .5 GPH at 50% load and .8-1.0 GPH at near 100% load. What's the difference here? Who goes by kWh?
Exactly the problem, right? The above information means nothing to anyone other than you because we don’t know what size generator you’re referring to.

Anyway, a kWh is nothing more than running 1,000 watts for an hour, or 500 watts for two hours, or 4,000 watts for 15 minutes. It’s all the same amount of electrical energy, and if generators were all equally efficient, they would use same amount of fuel (except for diesel vs gas difference).
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Old 05-08-2018, 10:34 PM   #4
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Interesting.

The inverter generators do not seem super efficient. I know they are quieter and power is cleaner but in my application, the open style works fine.

Before the RV, my old 5000 which still runs, was bolted to trailer for power at track. Then I was towing with Suburban. It would run 12-14 hours on 5 gallons. Though usually someone would bring me an extension cord and ask me to use in place of the old unit.

I do not know what Champion I use is rated at, but 3.5 gallons get me 12 to 16 hours. From inside RV, it sounds same as Onan 4000.

The Honda consumption shows is worth loading and matching loads.
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Old 05-08-2018, 10:53 PM   #5
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Quote:
Originally Posted by The Gritz Carlton View Post
Greek. This makes no sense to me, but...at my age not much does anymore. My manual says .5 GPH at 50% load and .8-1.0 GPH at near 100% load. What's the difference here? Who goes by kWh?
The idea is to convert them all to similar units so you can compare the different models against each other with meaningful values.

What I find interesting is how less efficient they are when running at less than 100% load (e.g. burn more fuel per kWh).
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Old 05-08-2018, 10:59 PM   #6
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At full load inverter generators are really no more efficient in general. Where inverter generators shine is as the load is reduced from 100% down to some load significantly lower.

Look at Onan diesel comparison:


3200 Watt RV Diesel (standard non-Inverter)

.12 gallons / kWh at 100% or 3200 watts

.19 gallons / kWh at 50% or 1600 watts


6000 Watt RV Inverter Diesel

.12 gallons / kWh at 100% or 6000 watts

.13 gallons / kWh at 50% or 3000 watts


Notice the efficiency of the standard diesel generator drops significantly at 50% power, whereas inverter generator efficiency remains almost as high.
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Old 05-08-2018, 11:02 PM   #7
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Originally Posted by JamieGeek View Post
The idea is to convert them all to similar units so you can compare the different models against each other with meaningful values.

What I find interesting is how less efficient they are when running at less than 100% load (e.g. burn more fuel per kWh).
Except when we combine “diesel” with “inverter”. I wish we had data at 25% load or even lower also, but expect its pretty good too.
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Old 05-08-2018, 11:29 PM   #8
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Quote:
Originally Posted by JamieGeek View Post
What I find interesting is how less efficient they are when running at less than 100% load (e.g. burn more fuel per kWh).
I was surprised by that little informational tidbit also...
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