# What size wire for generator?



## dcemery (Sep 23, 2007)

I am having a feed for a 30 amp/8000Watt portable generator installed including a 30 amp outdoor power inlet, a run from power inlet to two 200 amp panels in my home's basement of approximately 95 feet, with interlocks being placed on both panels. I would like to "future-proof" with awg large enough to handle a 50 amp generator in the future, if I decide I need it. Generator would be used only during power outages.

My question is:

What is the appropriate size wire to use in this situation which would also support 50 amps if I upgraded my generator in the future? I have quotes from 2 electricians, both of whom seem knowledgable, but one says he will use 6/3 Romex while the other recommends and has quoted 8/3 which he says will be enough for 50 amp if I need it in the future. 

I also asked the electrician who said 8/3 is adequate about voltage drop along this run. He says that it is not an issue with this wire until you get to 200 ft. I researched this on some various websites with calculators and I'm not sure that 8/3 awg is adequate, but what do I know? Maybe I'm not looking at this correctly. I would like to know any thoughts any of you might have. Is there a right and wrong answer here or is either one adequate?

I'd appreciate any input. Thank you.


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## Missouri Bound (Apr 9, 2011)

At 95' I would use the #6 wire.


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## adntech (Oct 25, 2011)

I too would use #6AWG.


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## J. V. (Jun 1, 2007)

Actually the voltage drop would be negligible. But the NEC has the last word. NM (Romex) cables reside in the 60 degree column of article 310.16. This chart shows #8 NM to be good for 40 amp and #6 NM to be good for 55 amp. So, legally you must use #6 NM for a 50 amp circuit breaker. Good Luck.


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## 47_47 (Sep 11, 2007)

Not an electrical answer, but if you currently have (2) 200 amp panels installed, what are your power demands and what do you want to do with a 30 amp generator?


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## jimmy21 (Jul 2, 2008)

47_47 said:


> Not an electrical answer, but if you currently have (2) 200 amp panels installed, what are your power demands and what do you want to do with a 30 amp generator?


As long as your not planning to run any major loads like water heater, heat, AC, kitchen stove, dryer, etc. You should be able to run damn near a whole house


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## 47_47 (Sep 11, 2007)

My point should have been, that if you are going through the expense of having a generator wired, make sure it is sized properly. If I lost power, I could heat, have hot water, cook and dry clothes in my house with 30 amp generator, because the appliances are all natural gas. 
Do not know the op's location, specific conditions, how often they lose power, but with 2) 200 amp panels, I would assume their house is all electric. I would consider having a generator installed that can power the HVAC to keep the house habital.


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## jimmy21 (Jul 2, 2008)

47_47 said:


> My point should have been, that if you are going through the expense of having a generator wired, make sure it is sized properly. If I lost power, I could heat, have hot water, cook and dry clothes in my house with 30 amp generator, because the appliances are all natural gas.
> Do not know the op's location, specific conditions, how often they lose power, but with 2) 200 amp panels, I would assume their house is all electric. I would consider having a generator installed that can power the HVAC to keep the house habital.



not that im arguing with you. Just discussing the topic at hand........... I've thought about adding provisions for a generator and even though my house is all electic, i could do fine with 30 amps of 220v. That would be enough to keep the stuf in my fridge and freezers cold. Be able watch tv, play on the computer, run the microwave, run a small heater, have lights. Basically be able to go about my normal day.
Wouldn't be able to cook a thanksgiving meal, take a shower more than once, or do the laundry. Those are sacrifices id be willing to make to save a lot of money.


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## dcemery (Sep 23, 2007)

Thank you for the input to everyone.

The portable generator would only be for emergency power outages, which fortunately occur rarely, like hurricane Irene- first outage in several years for us. As a result, I do not want to invest in getting a humongous portable- as long as I can get water (well pump) and have a few other things, that's all I need. However, if power outages become more frequent, would consider a larger 50 amp genny down the road.

So it seems that the general opinion is 6 awg is preferable over 8awg?


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## Missouri Bound (Apr 9, 2011)

In my opinion and using wiring and voltage drop calculations, #6 is the appropriate wire to use. And as the other posters eluded to, just choose carefully which circuits you want to use in the event of a power failure. The less the load on the generator, the better the fuel economy. I installed an 8kw standby generator a few years ago with a dedicated transfer panel. It controls 12 circuits only which I chose in the event of a power failure.


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## biggles (Jan 1, 2008)

i did a 3-#6 underground 75' for a 3500 watt always good to over size the wire and keep in mind your not max'g out the generator during a storm power outage ........tops 10A-15A on each leg


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## mblydude (Jan 4, 2014)

*Planning ahead*

I just came across this forum, as i am in the process of getting a generator setup for power outages. I realize that it is a couple of years old by now, but thought someone down the road might come across it as I had. 

Im not a licensed electrician but have worked a fair amount with some significant remodel projects with people who were. In most things home improvement, I tend to think ahead for potential upgrades down the road. (Im 32, and believe this to be our families home for good.) 

In a case, if I ever wanted to grow or add on later, and the cost difference is negligible now, might as well go with the #6. If you go with #8 then want to switch later, you are out the $ you spent on the #8, but then have to get the #6 still (which will only be more expensive down the road). 

Just my $0.02


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## mblydude (Jan 4, 2014)

UPDATE: I ran the 6G wire from the inlet receptacle box I installed on the outside of the house to the panel, for a 25' run. Hooked it up to the breaker panel and installed the interlock kit. The whole thing was pretty straight forward, and just took a bit of removing segments of drywall to have access to work the 6G cable into place. I was doing this all as we were getting a pretty good snow. After getting this all hooked up, I went to throw the main breaker back on to check that things were reconnected correctly...nothing happened.  

I thought I REALLY messed up, but stood there freaking out, looking at the panel going, "I KNOW it is hooked up right!". Then I thought I should call the electric company, and got a recording that there was a line down in our area and we were without power. :laughing:

Time to test the generator hook up then, right? Flipped the main back off, fired up the generator, flipped the breaker from the generator in the panel, and then moment of truth, flipped the breaker to the furnace and it kicked right on. 

Power was out for 36 hours and it was the coldest day in over 20 years. Could NOT have had a better timing to do this project. Thank you to the folks on this forum for helping me work out the details to do the thing right. :thumbup:


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## dmxtothemax (Oct 26, 2010)

Npkr01 said:


> What is the appropriate size wire to use in this situation which would also support 50 amps if I upgraded my generator in the future?


 
Generally in terms of less voltage drop, BIGGER is always better !
But the down side is more cost.

So if you don't mind paying a bit more get the 6 !

Then you can easily upgrade later on !


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## Toller (Jan 2, 2013)

Npkr01 said:


> Thank you for the input to everyone.
> 
> The portable generator would only be for emergency power outages, which fortunately occur rarely, like hurricane Irene- first outage in several years for us. As a result, I do not want to invest in getting a humongous portable- as long as I can get water (well pump) and have a few other things, that's all I need. However, if power outages become more frequent, would consider a larger 50 amp genny down the road.
> 
> So it seems that the general opinion is 6 awg is preferable over 8awg?


I strongly agree with getting the smallest generator you can get through a crisis with. Buying gasoline in an emergency can be impossible and big ones really suck it down. With that in mind, consider a propane generator. They are not much more expensive, but you can store as much fuel as you want indefinitely. Plus, propane might be more available in an emergency as most people would have no use for it.

But on your subject... I had a 2000w generator and put in 8/3 for it; about 4 times what I needed. The labor is the same, so why do it twice. So, yes definitely 6/3.


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## Sparks1784 (May 27, 2021)

So...I am considering doing the same thing as what is being suggested, but the replies are incomplete IMHO. The 7.5kw generator I am installing will NOT accept 6-3 AND an 8 wire control cable in the 3/4” hole (for 3/4” conduit) that the generator provides. What I am doing is running 6-3 to a junction box (3R enclosure) and running 8-3 from there to the generator. I think I could actually use 10-3 for the 3 ft run from the junction box to the generator but I will see how snug 10-3 is first.
This will allow me to leave the main 6-3 wiring in place if I ever upgrade to a bigger generator.


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## SW Dweller (Jan 6, 2021)

If you are considering future proofing for an electric car then the puny 50 amp circuit will disappoint. There are charger in developement that will require 100 amps 240v and that is before you get to DC-DC charging.


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