# efficient sizing for emergency gen



## chris124 (Oct 21, 2014)

Hi,
I'm about to purchase a portable generator so I can keep the heat on and periodically run the well and fridge.

I'm in northern NJ. I've had 3 major outages over the last 3 years, totaling 20 days w/o power. We also usually are unable to get out for 3 or 4 days - so I have to have gas for several days. Plus after Sandy, even once we could get out, gas was hard to get (few operating stations w/ power). 

I have a question about gas consumption. For example, if I'm using 2000 watts and have a choice between a 3000 watt and 7000 watt generator, will the per hour gas consumption be the same, or will one of these two generators be more efficient? Are these generators able to throttle back when not at full load??

Thanks for any insight -- Chris


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## aandpdan (Oct 8, 2012)

The bigger the generator the more fuel required, even at the same load. It's bigger, has more friction, mass, etc.

Yes you can get generators with an auto-throttle. 

Check your well pump however. What is the starting load? You may not be able to start the well pump in auto-throttle. The generator needs to be able to respond quick enough to the load.

Inverter generators are usually more efficient but are often only able to run 120 volt loads.


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## arubalou (Feb 9, 2013)

get about 6 5-6 gallon gas cans, hold onto them, as soon as they start talking about a storm get them all filled. if you dont end up using the gas you can just fill your cars tank with it.


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## chris124 (Oct 21, 2014)

@aandpdan,

I'll pay attention to auto-throttles. The well pump label says 4.8 and 5.9 amps -- I assumed that the higher number might be the start-up. If so, at 230 volts that would be 1104 running and 1357 start-up.

@arubalou, 

gas cans - a friend has a couple cans he fills if a storm is coming. Anything left over gets put into the cars.

Thanks for the feedback -- Chris


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## Waypoint (Jan 28, 2014)

It's tough to balance efficiency and capacity in a scenario involving an intermittent-use appliance that needs a lot of wattage...like a well pump.

You'll only need the big 2-phase gen for water pumping, the rest of the time a small inverter will do the job with minimal gas consumption and noise.

Maybe make a deal with a neighbor to split a used big generator?


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