how much fuel does a diesel generator consume?
If you’re talking about running a generator set 25% of the time, on 365 x 24 operation schedule, and sometimes for extended periods, fuel economy takes a back seat to reliability and serviceability. That’s a 2190 hour a year run time average, which is a lot for small capacity generator sets, which are often air cooled diesels. Larger sets are typically water-cooled, and have much better long term life and service requirements, as a result. Another thing to be aware of is that small diesels with few cylinders have terriffic torsional crankshaft resonances, particularly at high load, due to the nature of diesel operation. So a single cylinder 5Kw unit, while meeting the electrical load spec, is going to be beating its shaft coupling to death, doing it. A 2 cylinder 10Kw air cooled unit will last a lot longer, driving the same load, but it is still going to pound its motor mounts and shaft couplings to powder a lot faster than you’d see on a gasoline unit of similar capacity. A 20Kw 4 cyl
” The power budget for the whole system fits within 3/4 load factor on a 5kW generator. However we may end up with a larger unit such as 10kW to provide future expansion capability.” You’ve answered your question almost. If you are looking for overcapacity, that spec trumps the optimization selection of the smaller unit. Parallelling is also possible with generators, if they are phase synchronized. You could take that approach and add another 5 KW later, if you absolutely had to go with the smallest now. My guess is that the larger unit does not require “substantially” more fuel because the load is what is going to determine most of the fuel consumption. The difference between 5KW and 10 KW is roughly 12 HP, assuming 50% generator efficiency… so that’s about the engine size difference I’d expect…(just a guess). Generac and Kohler have a fair amount of on-line info regarding sizing. I’d contact them directly and pose the question. They are in business to answer such questions.
