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Let’s Talk SHTF Backup Generators (NG)


JohnC
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So for the coming blackouts as more EV’s are sold, plus natural disasters, I want to get a “Whole House” Natural Gas powered backup electric generator. 

I know it will need the switch panel and I would like Wi-Fi to be able to control it remotely via cellphone or internet access.

My electric bill from July had me at 53kw average a day.

The low average was 36kw and the peak was 76kw.

House is 3,200 sq ft with 711sq ft garage that I plan to get heated and cooled. Lots of appliances and stuff as my usage suggests (and I’m not home much).

I’m thinking if I go all out, a 80 or 90 kw would be perfect. I seen Cummins makes some real nice units that are decently compact and claim to be quiet. Most have  a 4cyl 3.9. 

So have any of you or someone you know installed a backup power supply? How much did it cost to install? How long did it take them to install it? Is it loud or quiet? What bran did you go with and why?

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Friend of mine has a whole home ginny. Runs on natural gas. It seems like he starts it occasionally, and it is very very quiet. I've not been around to see how well it works, but I does have all the automatic switching so if power goes, it fires and switches to it's control and when power is restored it switches back and shuts down. His house is about 4000sqft and 3 AC units. I think his ginny is like 20kW? Something like that. Not huge

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The online size calculator for Generac per home size and appliances puts me at about 30kw.

The Cummins site calculator put me higher.

But my electric bill tells another story!

My daily average use is 53kw.

My peak use 76kw.

If I go by my billed usage, I would shop for a 80 to 90 kw.

If I go by their calculator onCummins or  Generac, I’d shop for less.

Where is Mike Edwards! Halp! 

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I've helped.  You missed it.  Back to your words....  peak 76 kw per DAY.....80-90 kw per HOUR.  You've swapped units and it's messing you up.

 Want proof your house does NOT need  a generator as big as you think?  Simply  go to your main breaker.   What is your main breaker amperage?   A 200a main breaker at 220 volts is "only" 44,000 Watts.  44kw.  Total.  For the entire house.  Any more and POP goes the breaker.  You'll probably never use every electric device at one time to load it 100%.

A Watt is a unit of power, just like HP.    Volts times Amps = Watts.  Some of your stuff is 220v, some is 110v.

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Hmm… let me check my bill again to be sure… I think it was per day. If not, that could be the current draw peak (the 76kw) at any given moment. 

Can you compare my billed consumption to yours?

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I can compare your main breaker and input voltage to my main breaker and input voltage.

I'm 200a breaker at 256 volts.   Watts equals Volts times Amps.   In theory my breaker would trip if I put a load of more than 51,200 Watts.     I'm not scared to run my HVAC, a well pump, anything else in the house, and throw in a welder.

What is your main breaker?

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Last month I used 10 kWh.  At .115 cents per kWh, I was billed $1.25 for electricity.  I get a monthly $20.35 "facility fee" and 3% school tax, so the total bill is about $25.

Ready for SHTF lessons?  😄    (That's for my "under construction" house.   Two LEDs on continuously, running the well a few times, charging a few drill batteries.)

 

Where we live, a January bill I have handy...(family of 8, super insulated 2400 ft, geothermal HVAC, well pump, electric water heater/stove/clothes dryer)  1,700 kWh.

 

 

And go to your main electrical panel, open the cover, tell me what amp is printed on the main (big, top) breaker.  That will tell your max capacity, or is that ampacity?

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My cousin is an engineer at the East TN TVA Nuclear plant.

I set him a message and this was his math:

Quote

For how big of generator you should buy. The math would be total energy over month divided by total hours in month. So 1650/720=2.23 kW. Most residential load has about 20% load factor. So 2.23/.2= 11.45 kW peak power demand. This is pretty close to what I’d expect. You would be adding a few more kW. So anywhere from a 12-15 kW generator. If want to be safe get the 15 kW. But. All that said, not sure how many hours you without power but here I’m out less than an hour a year. So not very economic to put in generator. Maybe different there.

Disclaimer. He is not a backup whole house generator installer or engineer. There may be some sizing calculations he doesn't know to factor in. 

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I just got a bill.  My max was 90 kW.   Some math:  Amps(Volts) =  Watts.   My main breaker is a 200A(230V) = 46,000 Watts when the breaker trips.   Since that's WAY less than my peak, the numbers prove that:  A) "peak" is not instantaneous load, B) my breaker box can't handle any more than about 46kW of generator, C)  a family of 8 with "all electric" appliances doesn't need anywhere near 50kW of generator to run comfortable house.

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I settled for the 24kW Generac. They show they make 21Kw on NG.

It’ll be delivered today. Lee company will be here the 09/01/22 with their “project engineer” to quote the install.

In a outage, I can reduce my electric consumption and live with the 24kW generator comfortably. 

Heck, my cooktop is NG, my water heater is NG, my HVAC heat is NG, so I think I’ll be fine.

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In reality, that was probably double or more what you actually needed. 100% way to know is take an amp meter and put it on each phase coming in to your panel. Turn on everything you'll want running and see what the amps are. size a little higher than that to account for compressor start ups and such. 

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33 minutes ago, Ashley P said:

If my house were NG water heat and stove, our current 7500 watt generator  would be fine for all other stuff.

I have a 7500w that I use for our whole house. I installed an outlet (inlet?) on the outside wall next to the panel and when needed I just roll the ginny out and plug it in. I've not tried to run EVERYTHING, since I have two AC units, but it's fine to run all the important stuff. I have NG heat, water heater, and stove. 

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We're forgetting one very important thing.. This is all for normal people. we know JohnC is FAR from normal.

He said SHTF. That happens, NG will stop flowing. He needs to be looking at all solar.. and portable... He NEEDS an RV

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11 hours ago, mstrpth said:

We're forgetting one very important thing.. This is all for normal people. we know JohnC is FAR from normal.

He said SHTF. That happens, NG will stop flowing. He needs to be looking at all solar.. and portable... He NEEDS an RV

Not that kind of SHTF.

Ice storm, tornado’s etc…

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9 hours ago, Ashley P said:

IMHO, "WiFi equipped" will likely be the CAUSE of SHTF.  

Nope!

WiFi doesn't have anything to do with it being a reliable backup. The WiFi is just a way to monitor the units health, etc.

Quote

Mobile Link™ Wi-Fi Connectivity FREE with every Guardian Series Home Standby Generator

allows you to monitor the status of your generator from anywhere in the world using a smartphone, tablet, or PC. Easily access information, such as the current operating status and the generator’s maintenance schedule. Connect your account to your authorized service dealer for fast, friendly and convenient assistance. With Mobile Link you are taken care of before the new power outage.

 

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