# generator fuel consumption



## Szumi

Right now I'm looking at the Generac Model 5939 5500 Watt Portable Generator. It lists fuel consumption at 0.72 gallon per hour at 50% load.

What if you are only running 25% load? Does fuel consumption scale linearly?

I'm trying to buy big enough, but not too big, in case I have to run this for an extended period the next power outage.

Thanks,

Szumi


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## Jason

We have a 6000 watt portable generator that we usually just use around the farm for odds and ends type stuff- putting a battery charger on a tractor that's not parked near an outlet, etc. I'm not even sure how much fuel per hour it uses but I do know that the more power it's making the harder the engine works, so he more fuel it uses. I'd think at a lighter load you'd see significant fuel savings but I'm not sure if the fuel to power ratio would remain the same.


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## staceyj

Even at 25% load the engine will have to turn enough RPM's to keep your frequency at 60 hertz. With that being said I do not think it will burn leas fuel than what is stated.


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## Luke1

Why not spend money and get a solar powered portable generator?


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## Tirediron

Your fuel curve will not be linear,it probably uses less than 1.44 gallons at full load , it might get somewhat better at 25% load maybe .5 gallons per hour, depending on the efficiency of the design, you would probably get your best wattage per dollar from intermitant operation where it could run at closer to capacity.


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## Szumi

Tirediron said:


> Your fuel curve will not be linear,it probably uses less than 1.44 gallons at full load , it might get somewhat better at 25% load maybe .5 gallons per hour, depending on the efficiency of the design, you would probably get your best wattage per dollar from intermitant operation where it could run at closer to capacity.


I'm fairly sure it won't be linear either. I see that Generac uses the same engine across a few different wattages while quoting .72 gph at 50%.

Running it in spurts is likely the most fuel efficient method.

Looking at my daily usage via the smart meter, I use about .9 KWH per hour.

Sadly, the math doesn't work when the fridge, pump, and furnace kicks on. Running the washer and pump would also be a killer for a small generator.

They make these hybrid cars, I wish they would make a hybrid portable generator, a 2KW output electric start with inverter. The inverter would perform two tasks, covering short time instantaneous peaks so you can use a smaller engine and when loads are small, run off the battery, then start the generator if loads increase, or when the battery needs recharging. You would need two batteries so you wouldn't drop loads during a start.

Szumi


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## Szumi

Luke1 said:


> Why not spend money and get a solar powered portable generator?


Was that supposed to be helpful?


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## fondini

Szumi said:


> Was that supposed to be helpful?


I have been looking at the solar powered ones, pricey, but may be a solution to look at. I have noticed that other brands have better feed back than generac does for long term. One big plus when the fan gets funky, you won't have to worry about fuel. ( sorry add must've kicked in, the generac comment was referring to gas/diesel ones) best of luck


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## Luke1

If the shit really hits the fan the sooner or later the gas WILL run out, solar power is the way to go.


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## partdeux

Most gen sets are most efficient at nearly full load. There are a LOT of parasitic losses at low usage. I'm beginning to lean towards a smaller gen set for occassional light use, and saving my med size unit for when it's really needed.


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## GaryS

My 20KW whole-house generator burns nearly as much during periodic warm-ups as it does when powering the house. The governor keeps it at the same RPM whether loaded or not, and engine speed seems to be a bigger factor than load.


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## Tweto

I have a Miller Bobcat welder/generator. It does both great. The advantage is if you are not drawing power it idles down. If you start drawing power again it powers up in 1 second. At idle it is using considerably less fuel. If I run accross the operators manual I will post the fuel usage difference.

These welder generators can be purchased as a 6KW and up to 20KW.


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## Szumi

I spoke to my brother, the electrician, he told me most people buy too big a generator. I'm thinking seriously of buying a Generac XG4000

This is a Generac with an oil filter, something I hope will live longer if it has to be used in more than a couple outages.

Going down in power gets me into the .32 gal / hr at 50% range I won't be able to run everything at once but I can run enough and more importantly, run stuff a lot longer at a time.

Instinctively as a guy, I want to buy bigger and better, this seems like something where better is okay, but bigger isn't unless you really need it.

Szumi


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## mpguy18

Tweeto, what do these run? They would have a great benefit with fuel comsumtion prior, and great usefulness after a shtf.


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## Tweto

mpguy18 said:


> Tweeto, what do these run? They would have a great benefit with fuel comsumtion prior, and great usefulness after a shtf.


New, they run about $4,000, but I see them on E-bay used for half that. that is for a 10KW version. I bought mine about 15 years ago and paid $2100 new.


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## outsider

Check out the Honda line of inverter generators. They use a small fuel efficient motor. They are more money but very quiet. Nothing like drawing attention with a loud genset. They are also great for camping and boating since you can stand over it and have a conversation.


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