Generator Fuel Consumption

[hmason]

Under the guise of "no question is stupid," I would like to know if a generator which should run at a constant RPM, uses more fuel under a heavy load than it would use under a smaller load. Is it like a car going uphill and using more fuel to maintain RPM? Thanks, Howard

 

[bayview]

yes, it uses an amount of fuel necessary to produce the amount of power generated. More watts equals more fuel.

 

[hmason]

Thanks. I thought so but wasn't sure.

 

[Ski in NC]

Just going from foggy memory, a typical 8kW burns something like this:

0% output: 0.25gph
50% ouput: 0.5gph
100% output: 1.0gph

So yes, burns more under load. About 0.25gph is needed to just run the unit and that amount is always being burned whether you use the power or not. Don't quote me on the numbers, just for example.

 

[Alaskan Sea-Duction]

That sounds about right. My owners manual states at full load it burns 0.9gph for my 8KW.

 

[Richard W]

FWIW, from my notes ...

GENSET FUEL USAGE
Kohler Generator 5ECD
Fuel Consumption at 120V AC 60 Hz
LOAD LPH (GPH)
100% 2.84 (0.75)
75% 2.61 (0.69)
50% 2.31 (0.61)
25% 2.04 (0.54)

 

[hmason]

Thanks all. Howard

 

[eyschulman]

Another way of looking at it is for every 20 Hp put out by almost all diesel engines one gal. of fuel is burnt per hour. The reason for this relationship is based on how much energy can be extracted from diesel fuel. And as mentioned above in prev. posts its not the RPM its the load or work that counts. You can rev your motor in neutral to WOT and burn little fuel. So if you know the HP ratting of a motor and have a good idea of how much it is loaded you can estimate fuel burn. This is what newer motors with electronic inst. due by converting % load to fuel burn info. usually but not always accurate.