Portable power generator ballpark fuel consumption
tl;dr What is a likely value for fuel consumption for a small portable 4-stroke gasoline-powered inverter power generator in, say, litre / ( kilowatt * hour )?
At times I attend music festivals where you camp outside for a few days and go see bands perform in the afternoon and evenings. Some of them permit the use of power generators, and I got myself one as described above rated for max. 1000 watts continuous power draw. My group won't use that much, but that's what I got when I aimed for the smallest 4-stroke inverter model.
Among my questions is now how to estimate the amount of fuel to bring with me to a given event, and unfortunately the spec sheet and other resources shipped with the unit do not feature any fuel consumption figures/curves/tables.
I do have a rough estimate of the power draw and duration.
Typically the power generator will be run from the morning into the afternoon, let's say 08:00..14:00, which is when people hang out at the camp site killing time until the bands start. From afternoon on it's seeing the bands until late into the night, after which people come back exhausted and in various stages of inebriation and usually just drop into their tents – running a generator at that kind of time is a jerk move that is guaranteed to bring the rightful wrath of your camp neighbors upon you.
While the generator is being used you will run a fridge for the drinks, some music setup for nice tunes, and a bunch of small power supplies charging various devices such as smartphones and power banks. If you're fancy you might have a table fan for when it's really hot. So let's add these up:
- 80 W - (small) fridge
- 50 W - music
- 5 * 10 W - smartphones etc. being charged
- 40 W - table fan
That's 220 W of continuous power draw (the fridge will be running its compressor continuously because it starts out warm and is made extensive use of). Multiply that with the 6 hours of daily use and we get about 1300 Wh, and if the festival lasts for 4 days we're at about 5300 Wh, or 5.3 kWh, drawn at roughly a quarter of the generator's rated output.
So … how much gas does that roughly equate to? I have been searching around for some ballpark figures, but I only seem to find various tables that are too specific and not readily applicable to my problem.
This post was sourced from https://outdoors.stackexchange.com/q/21691. It is licensed under CC BY-SA 4.0.
1 answer
Generator run time per gallon varies greatly by manufacture. Just like gas mileage varies per vehicle. Not all small 4 seat cars, driving the speed limit get the same gas mileage, even though they are doing the same work.
Most manufactures include run time per tank or gallon in their literature. Searching online for your make and model of generator should get you answers for your generator.
The are two primary markets for portable generators.
Construction workers
Campers and Survivalists
Both have minimum run time requirements, Construction works want the generator to run while the are working, at a minimum 4 hours. Campers want their generator to run all day, at a minimum 8 hours. As a result most generators run between 5 and 10 hours on one tank of fuel at 50% of rated output.
Personally I run my generators at home, at least twice a year (Spring and Fall), to ensure they are ready for the coming season.
When test running your generator put about a 1/4 tank of fuel in it. Plug in some things and and let it run until it runs out of fuel. This should be between 1 and 3 hours, multiple by 4 and that is how many hours it runs on one tank of fuel.
Fuel stabilizer is important. I always add fuel stabilizer to the fuel I run in my generators. I never know when I will run it again, but I know it could be 6 months, so stabilizer prevents gas break down. At the end of the season I put left over generator fuel in my car/truck and get new fuel (adding stabilizer) for the seasonal test run and reserve fuel.
Edit
No load requires about the same fuel as 50% or less load.
More load requires more fuel, there are multiple ways for manufacturers to balance fuel supply for increased load. Some of these solutions are less efficient then others. If it is important that you have good estimates on fuel consumption per hour, testing (per above) is your best choice.
For really ballpark estimates, figure 4 hours per tank, and in most scenarios you should be fine, with a little extra just in case.
For more info on why inexpensive generators don't scale kWh to fuel consumption see This answer at 'What to look for in a portable generator?'
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