# Power question, not necessarily "alternative" - sizing generator



## KC8QVO (Mar 22, 2011)

I know this isn't really an "alternative energy" question, being a fossil-fuel source, but power generation none-the-less. Maybe some here can offer some input. 

We had a storm blow through a week ago and some of my family has been out of power ever since. This got me thinking about back-up power sources a bit more. 

I am an alternative energy fan, I have a solar panel I use with my Ham radio when I am out and about. I would love to go off the grid totally on wind/solar. That is my dream some day.

Until I can get there - I think a generator is in the cards. 

Dad has a generator that is 5500 watts and I've been with him several times when it was in use. The last time was when the remnants of Hurricane Ike blew through Ohio a few years ago. This generator is enough to run the refrigerator, chest freezer, and all the lights/fans we can plug in to it. 

I did a little bit of searching and came up with some numbers for AC units - 3500-5500 watts. This would potentially put an AC unit in-range of dad's generator, but not a whole lot else. 

When I got word of my family's outage here in town I happened to be with my dad that day and down the street from my grandparents. They have a 2200 watt generator so I grabbed it, but dad warned me he couldn't get it started a couple days before. Long story short it took me over 10 hours to get it set up (cleaned out the whole fuel system, carb, etc then threw the whole tank in the trash). My family that was out of power is off city utilities - well and septic tank. So that means no electricity = no shower, no toilets, no sinks. 

So I did some looking around at well pumps. Long story short - it looks like a no-go for running a well pump on the 2200 watt generator. At least they have fans and lights, but still have to go find a tree in the middle of the night. 

For portable power I bought a Xantrex 1000w sine wave inverter several months ago. I run power tools and a service monitor off of it when I am on the road for work. This works out GREAT for temporary power. It has enough juice to run all the lights and fans we need in the house. But, that's the problem. #1 that is all it will run, plus tools if need-be, no microwave, no skillet, refrigerator, etc. #2 running any higher current devices that it WILL run (or combined current) drains batteries VERY quick. Even a light load (a light and a box fan, for example) will drain my diesel truck's 2 batteries in 4-5 hours. That is not enough run time, and I don't want to have to start the truck every hour for 5-10 minutes to charge. 

With the heat wave we have been having here in Ohio the last couple weeks I've really been giving consideration to air conditioning. I don't know how we would get by without it. I suppose we could all move in to the basement, that would be interesting. In any event, the AC unit here is a 3 ton unit. I checked the sticker and the min current requirement is 28 amps/208-230VAC. That is between 5824-6440 watts. 

Something else to consider in sizing a generator is fuel consumption. The smaller generators sip fuel compared to the bigger ones. A ~2000w generator will get about 11 hours on 3.5 gallons at half load, whereas a ~8000w generator will get 10 hours on 9 gallons at half load. Big difference, but also a big difference in power capacity too. 

So my questions. 

1. How much power should I really equate to being consumed by the 3-ton AC unit? The higher number (6440w)? 

2. How much more power should I factor in to allow for running a normal size refrigerator and a small refrigerator plus lights and fans? Maybe 500-700 watts lights/fans and 2000 for the two refrigerators? 

3. Diesel or gas? Or??? 

4. I could use a generator more often than in the dead heat of summer, and that means the heavy load of the AC is not going to be required. Would any of you think it would make sense to get a small generator (1800-2000w) to supplement the big one? Or would you just get a big one and settle for the higher fuel burn rate at the much lower current demand? 

Anything I get will have to be a wheeled portable unit (unless its small enough to carry around).


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## Newlife (May 27, 2012)

Not sure I can really answer your questions all that well; so I'll defer to someone with more expertise.

Here's a couple of thoughts. When the power goes out (like with a wide-spread storm), how is fuel availability? Most gas stations aren't able to pump gas without power. That means driving quite a ways to hopefully find some gas and hauling it back or storing enough at your house to get you through the burn rate of your genny.

Propane does have the advantage in that you can store it safely and easily and even if the power goes out, it isn't as hard to get as gas/diesel. You may want to consider a tri-fuel generator to cover all the bases.

Now, for what I did. Given my abilities to store fuel (limited) and the fact that I wanted a generator I can use as a portable power source, I went with a smaller inverter generator. It sips gas and allows me 2K+ watts for a long time without making a lot of noise. I also got a small window AC unit, which is enough to keep one bedroom icy cold or keep some common rooms (living room/kitchen/dining area) comfortable enough. The little inverter generator is small enough that I can just pick up and carry anywhere and has "clean" power for running computers and other more sensitive equipment.

If you are looking at something just for backup with the least cost or logistical issue; then doing something similar to what I did may be a good option.
If you have some more funds, and the space for fuel and equipment, the a whole house generator (diesel or propane for better storage) would be a better option.

Here's a link Portable Generators @ Electric Generators Direct.com - Portable Generators For Home, Portable Power Generator, Portable Generators, Portable Generator For Home, Portable Power Generators, Portable Generator, Generator Portable, Generators Portable
They've got a lot of information and some very knowledgeable people who work there and can give you a better idea on sizing if your really still want to run the whole-house AC unit plus a few other things.


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## Ross (May 9, 2002)

Fridgs don't really need that much power nor need to run all the time. We ran ou freezer on an 800 watt camping gennie and the TV lights and computer (honda genny through a battery back up/filter) and it was fine. Pumping water needed the 5000 watt Honda but it was a 3/4 hp well pump too! If you need AC (esp a 3 ton unit) you're going to need a much bigger generator plus adding water and refrigeration.... think more like 20,000 watts and not the surge power rating either. Thing to do is the add up what you need to run (rating plates and get some local help from a good generator sales office. You probably do need a diesel or propane unit and its not going to come cheap. We make do with small generators and the expectation of needing to cycle our uses, and no AC or electric heat of any sort but we could run our small window units if we had to.


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## KC8QVO (Mar 22, 2011)

Anything I get will have to be a "portable" generator. If its on wheels I can get it in my truck, even if its a couple hundred lbs I could manage it with some ramps. 

I didn't really consider fuel availability. That hasn't been much of an issue, though. Even when the remnants of Hurricane Ike came through we could still get gas within a reasonable distance, and that is the most wide-spread power outage I remember. 

Ross - you make good points. I need to see what the power needs are of the fridges. You're right though, those don't need to run all the time. Its quite possible we can get by with a lot less power in that regard.

The AC unit, like times like now (a strong heat wave) would run constantly so that would be a large draw. I don't have a direct need for running a well pump, but that isn't to say I won't in the future. 

I have a room AC unit running right now in here as a supplement to the big one. Its 7.6 amps, so 912 watts or there about. Its a bigger one than what is at my cabin too. If I got a smaller generator, around 2000 watts, I could quite possibly be able to run the small AC units and fridges, plus lights and fans. That may be the way to go for now. If I could figure out how to add a bigger fuel tank that would be even better (get ~12 hours or so at load, not 3-4).


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## wy_white_wolf (Oct 14, 2004)

Deisel and propane will store longer than gasoline so you wouldn't have to go through the trouble you did with the grandparents little genny.

If the genny is oversized you can still run everything. Undersized and you'll have to play load controll by turning things on and off. Total up all your loads you want to run at the same time and add 25% minimum.

Adding a larger tank isn't hard but don't go too much taller. Most gennies are gravity feed and the extra hieght can make them run rich.

WWW

WWW


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## Jim-mi (May 15, 2002)

Life would / could be easier $$$$$$ if you could knock the big AC unit off your list.

I would think your gp-around with old gas would take gas off your list........
But then diesel can grow alge in time also......

I'm seeing more and more small diesel gen's "on wheels" available . . .don't know the quality of the no name stuff......
Should be much better quality if it is Yanmar or Kabota diesel powered.

Yes I have seen add on fuel tank kits on flea-bay........

I have to admit that a add on tank to a Honda 3000i (inverter) gen would make a very attractive gas powered unit.......


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## wy_white_wolf (Oct 14, 2004)

Jim-mi said:


> ...I have to admit that a add on tank to a Honda 3000i (inverter) gen would make a very attractive gas powered unit.......


Not sure about the 3000i but I know they made one for the 2000i. It was simple a replacement cap for the tank that had a hose hooked to it that ran from another tank. I think it added a gallon or so to the capacity.


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## KC8QVO (Mar 22, 2011)

Jim, 

I've had/have all kinds of gas powered equipment so grandpas generator doesn't scare me too much, though my riding mower has sat for a few years. If I had to pay someone to fix the generator they'd say throw it out and get a new one I'm sure, but I can fix stuff like that (with time and effort). That isn't to say I like to do that, but I can if I have to. When I am at the cabin I'm the only one that can do a lot of that therefore I am the only one that does it  Vacations are supposed to be vacations, mine go the other way.

In any event, I think I have things nailed down. The Generac iX2000 is on top of my list and a XG8000 is down the line. I have one more item I need to check on in regards to the iX2000. I thought about everything we need at the cabin and the highest draw device is the water pump. It is a 110v unit, I was working on that system a few weeks ago but I never paid attention to what it is. I got a model # so let me see what I can come up with on specs. If it is within the 2000 watt limit I'll have my choice. If not, I'll have to do some more digging. I'd like to get a generator to keep up there, but I can't do that because it will grow legs (or, ski's) over the winter months. 

The 2000w class will run everything I need minus the big AC, and questionably the pump at the cabin. It will run both the portable AC unit I have here, at the cabin, and all the refrigerators.


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## Jim-mi (May 15, 2002)

Careful of the inrush (surge) of that well pump.

A 2000 isn't likely able to handle it . . . without damage ......

Far better to have a unit with some 'reserve' power than pushing a small unit right to the edge.


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## artificer (Feb 26, 2007)

wy_white_wolf said:


> Not sure about the 3000i but I know they made one for the 2000i. It was simple a replacement cap for the tank that had a hose hooked to it that ran from another tank. I think it added a gallon or so to the capacity.


The honda inverter generators have a vacuum pump for the fuel. The axillary tank uses a cap with a hose in it. You run the hose to the second/auxiliary tank, and have as much fuel as you want, since the vacuum draws the fuel from the auxilary tank, and feeds it into the main tank. I'm using a 6gal boat tank, so I have just under 7 gallons of fuel to use. My tank uses a quick detach for boat tanks to disconnect the tank from the generator. You can buy the second cap, or modify the one that comes with the generator. If you modify the one that came with it, you need to make sure it can breath if you don't have the auxiliary tank on it.

They make soft start kits for pumps, so you can tame some of the inrush current when the pump starts. RV AC units have them, in many cases.

Michael


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## KC8QVO (Mar 22, 2011)

artificer said:


> They make soft start kits for pumps, so you can tame some of the inrush current when the pump starts. RV AC units have them, in many cases.


Great info Michael. I was not aware that there was such a thing. That could make or break the set up.


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## motdaugrnds (Jul 3, 2002)

Great information in this thread. Thanks KC8QVO for starting it.

Ross, when you say you "...could run our small window units..." on small generators, are you talking about "refrigerated air" window units or simply fans placed in windows? (Just pm me please as I don't want to hijack this thread.)


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## artificer (Feb 26, 2007)

motdaugrnds,

Our EU2000i starts the 5,000btu window unit with no problem, even on eco mode. RV people talk about starting 13,500btu units. Some need hard start kits, some don't.

One nice thing about the Honda, and probably most inverter generators, is that you can "stack" them. Get a power cord, and you can connect two or more generators together to get the power you need. Then again, you can get several high power screamers for the price of one Honda inverter generator.

Michael


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## Jim-mi (May 15, 2002)

Thats a VERY good point that I haven't seen on here.

The cheapos are VERY noisy . . . ."screamers" . . .for sure.

Yes if one wants to go with "gasoline" a stacked pair of Honda EU2000i 's would be sweet . . tho pricy...........


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## motdaugrnds (Jul 3, 2002)

Thanks, I know I don't want the "screamers" and pricy is ok as long as I know it will do the job for us. I just found the information about the air conditioner I want a generator (propone) to run for us.

It is Kenmore model #580.75281500
Serial #512KAZK02197
Watts 3,230/3,290
Amps 15,8/14.6
60 Hz
Cooling capacity 27,500/28,000 btu
design pressure: H.S.350 psig and L.S.150 psg

If I can run this during summer months on a quiet propane generator (maybe a stackable one if the need arises to need one), I can cut near a thousand dollars of my bills during the heat of the summer.

Any suggestions as to which generator I need to get and why would be appreciated. (Even a private message would be ok so as not to hijack this thread.)


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## Darren (May 10, 2002)

Before you buy a Generac, do a google search using Generac and problems. Here's one result. Be aware that Generac uses Chinese engines in some models. Also look at the Generac warranty. It has a clause that potentially invalidates the warranty if you run the unit in a long power outage.

Generac Air Cooled Generators - Ziller Electric Inc | Interactive Generac Generator Forum


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## nadja (May 22, 2011)

You may want to look at an older rv gennie also. I have had two 4k onans, which after many years , sold them to my neighbor, when I bought a 25 year old Kohler twin 7k. The Kohler had only about 200 hours on it as most are not used much in rv's. It cost me 200.00 plus another 180.00 for parts and labor to "re condition" it. Works like a champ. I have lived off the grid on solar/wind now for over 16 years, and when like now, the monsoons roll in, not much sun, but lots of clouds. So have to run the gennie to charge up my battery bank. The rv twins actually run very quiet and do ususally require a gas tank, as they normally run off the rv's tank. You can get them in propane if the unit is propane or diesel etc. Propane would be the best as the fuel never goes bad. They are made to run hour after hour, while the chinese screamers are not. 

One of the reasons for the small inverter gennies have such small gas tanks, is weight of course, but even more important, is to let them cool off for awhile , while adding more gas. The little guys are not made to run indefinately.


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## Ross (May 9, 2002)

motdaugrnds said:


> If I can run this during summer months on a quiet propane generator (maybe a stackable one if the need arises to need one), I can cut near a thousand dollars of my bills during the heat of the summer.


 How is running a generator going to save you thousands? Grid power is cheaper by quite a bit. Wow your AC is not a small one, at least it wouldn't be here. 12,000 but is a big unit here 5-7000 would be small. 
I wouldn't say you're hijacking the thread mearly broadening its paramitors!


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## KC8QVO (Mar 22, 2011)

You guys aren't hijacking the thread much, good discussion. 

I was running some numbers on cost of running a generator. Of course, the fuel burn rate is the most important factor to nailing down the cost to run. I figured all my numbers on running for a week straight. That is 168 hours. 

Small generators can have a burn rate around .3 gal/hr (between 1200 and 1800w draw, not the actual running rating of the unit). So if you figure .3gal/hr average use for 168 hours (a week of no power) you're looking at over 50 gallons of fuel burned (50.4 to be exact). 

Bigger generators, with say 3-4000w draw or 6-8000w rated, have around a .8gal/hr burn rate. Using the same numbers that comes out to ~134 gallons of fuel. Big difference. 

Even more, 5-6000w draw from a 10-12,000w rated unit you're looking at ~1.3gal/hr, or 218 gallons burned. 

Now factor in fuel. Gasoline at 3.60 a gallon (just an off the wall number, about what regular is here right now) would put the small generators at a cost of running at $181.44, middle size at ~$483, larger at ~$785. 

Then how do you supply that fuel? 130 gallons is a lot of fuel to stack up, let alone over 200 gallons.


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## KC8QVO (Mar 22, 2011)

Darren, can you get me a direct link to the thread you are referencing? The link you provided goes to the parent forum, not the thread.


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## Newlife (May 27, 2012)

Just something else to consider when comparing costs on the generators is maintenance. Oil changes, spark plugs, filters, etc... all that needs to be added. Oh, don't forget the cost of obtaining fuel (storage containers, trips to town, etc...)

That said, does anyone know of any websites that might discuss recharging an off grid system with a generator? Just trying to get an idea of what size might be needed, how long it would have to run, any special controllers needed, etc...

Now back to your regularly scheduled thread


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## KC8QVO (Mar 22, 2011)

Newlife said:


> That said, does anyone know of any websites that might discuss recharging an off grid system with a generator? Just trying to get an idea of what size might be needed, how long it would have to run, any special controllers needed, etc...


That's funny. I was thinking about that this morning also. Someone posted a link to Sun Electronics for deals on solar panels. I got to looking around at the emergency power and off-grid systems. It would be pretty slick to do that, but if you have a period with very little solar charging conditions and need power a generator would have to be used there too. Since everything would already (hopefully) be run on the solar system the only use the generator would serve is to crank juice in to the battery bank. 

Or you could supplement the solar with wind turbines. 

You're right on the other costs too, I was just looking at fuel being a sole parameter. If I was out in the boonies trips to town might be an issue, but everywhere I am isn't too out in the boonies. Even my cabin is only a couple minutes from a gas station (then the question of if power goes out can I get gas comes in to play).


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## Darren (May 10, 2002)

If you're in an area that produces natural gas consider using that to fuel the generator. Natural gas is really cheap right now. The fact you won't have to have fuel delivered or get it yourself is the icing on the cake.


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## Jim-mi (May 15, 2002)

Looking at the "Generac" gennys I saw that a very good $3800 6KW propane unit under heavy load (80 to 90 %) -----Big AC and lots of refrigeration---- will use 1.25 gallons per hour. . . . .Far less than that when the load is light. 

Big AC's are huge hogs . . . .
Big hogs seem to have bottomless pits when it is "feeding" time . . . .which is all the time


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## KC8QVO (Mar 22, 2011)

I'd like to find what the no-load fuel consumption is of some of the small conventional units, like the XG4000 Generac. If the fuel consumption is really light that might be the route to go for me. 

In another thread someone brought up people running more than 2 Honda units in parallel, though Honda says you can only do 2. I would think 2 of those could run the water pump at my cabin, but I can't be certain.


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## nadja (May 22, 2011)

Newlife said:


> Just something else to consider when comparing costs on the generators is maintenance. Oil changes, spark plugs, filters, etc... all that needs to be added. Oh, don't forget the cost of obtaining fuel (storage containers, trips to town, etc...)
> 
> That said, does anyone know of any websites that might discuss recharging an off grid system with a generator? Just trying to get an idea of what size might be needed, how long it would have to run, any special controllers needed, etc...
> 
> Now back to your regularly scheduled thread


I am doing almost that right now. I live off the grid, and my solar system is not putting out much due to the high clouds from the monsoons. So, almost every night I have to run my gennie for about an hour or so to bring my battery bank up to snuff for the evenings. There is nothing wrong with that, although it does cost money for fuel and lots of it for the next few weeks. Also, you really need to factor in the cost of the generator and maintenance for that time

As far as how long does it have to run, it depends on several things, such as the size of your battery bank and the charge of existing batteries when you start the charging. Are you planning on living on batteries without solar just using a gennie to do the charging ? If so, you will wear out at least one generator a year


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## Jim-mi (May 15, 2002)

I just dug out my professional K.I.S.S. kall-que-later...
K.I.S.S. --- keep it simple stupid.

Lets say--only-- 12 hours a day for big AC
round it off to--! gallon an hour
And bargin priced propane at $2 per gallon

Wee . . . $24 bucks a day

Times a week=

holy toledo . . . . . . . . .$168 a week .. . . . just for fuel




guess the grid price (currently) isn't so bad afterall.


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## artificer (Feb 26, 2007)

That said, does anyone know of any websites that might discuss recharging an off grid system with a generator?

If you go to Microcogen.info/***/SOMRAD Forums - Index, you'll find a lot of information about engine powered DC chargers.

Now, back to AC and generators...
You have to be careful when you compare fuel useage rates.

Generator	EU2000i	EU2000i	EU3000is	Eu3000is	EM4000s	EM4000s	EU6500is	EU6500is	EM6500s	EM6500s
Fuel tank cap	1.1	1.1	3.4	3.4	6.2	6.2	4.5	4.5	6.2	6.2
% of Load	100	25	100	25	100	50	100	25	100	50
Rated watts	1600	1600	2800	2800	3500	3500	5500	5500	5500	5500
Run Time	4	9.6	7.2	20	10.1	16	4.7	14	6.9	10.4
Fuel usage	5.82	3.49	5.93	4.12	5.7	4.52	5.74	4.28	6.12	4.61
GAL/KW-HR	0.17	0.29	0.17	0.24	0.18	0.22	0.17	0.23	0.16	0.22

Its a bad looking chart, but look at the bottom line. For a fully/highly loaded generator, the screamers actually get better fuel numbers than the inverter one. Its reversed for light loads, since the inverter generators will idle down, and run slower to save fuel.

Now, for the power useage. 3,300 watts of power draw
cost @$3.6/gal/hr	2.04	3.4	2	2.89	2.08	2.63	2.07	2.78	1.94	2.58
Cost @ $.20/Kwhr/hr	0.66	0.66	0.66	0.66	0.66	0.66	0.66	0.66	0.66	0.66

If you calculate cost for the same energy useage, you'll see that a generator can't compete with the grid for power. If you run a smaller AC unit on a smaller generator, it will use less power and cost less, but it will cost even less if just left connected to the grid. It gets even worse if the compressor in the AC unit kicks off for awhile. Now the generator is running lightly loaded, while the power company only charges for what you use.

Short answer (too late!!!) is to get a properly sized backup generator that can handle the load while the grid is down, but you'll never save money running it if grid power is available.

Michael


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## KC8QVO (Mar 22, 2011)

I just got the numbers for my water pump at the cabin. Can someone help me out with them?

Here's what I got:
Dual voltage
1/2hp
9.6/4.8A
11.8/5.9A

I am guessing that the amperage ratings are for 110vAC vs. 220vAC. Is the 9.6/4.8A for 220 and the 11.8/5.9A for 110? 

If I take the high number (11.8A) at 115vAC that is 1357 watts. That seems quite lite. Is that right? What about starting current? Multiply that by 1.5-2? 

This is going to be the single highest load I will have to run on my "portable" generator(s). The refrigerators are all much less. I measured our secondary here at the house at 600w starting/530w running, for example. The cabin fridge is bigger and our main fridge here at home is bigger still. 

I am thinking the Generac XG4000 is still a good route to go. This looks like a good choice for the cabin. Then a pair of Honda EU3000is's paralleled would be a good choice for at home. I can split off one of them for portable power camping/ham radio events and run the two at the house when needed. Then for the big generator a Generac XG10000 as a plug-in unit with a transfer switch. This will start and run our AC and lighter loads through the house when needed. When the AC is not needed, if just running light loads a single EU3000is would do, or 2 paralleled if I needed a bit more. Thats 4 generators, but in terms of fuel consumption it is the most flexible scenario.


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## motdaugrnds (Jul 3, 2002)

So you are all saying that if I get a generator (propane) to run my 28,000 btu air conditioner 3 months during heat of summer, it wouldn't save me any money? [Those 3 months during the heat of summer is when I would be spending $200-300 monthly for electric bill. When the air conditioner is not used, this electric bill (even during cold winter months) is less than $100 each month. So I need to find a way to save money during these heated summer months]


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## KC8QVO (Mar 22, 2011)

The cost per kwH of electricity with the generator is going to be exponentially higher (fuel cost). Add in the cost of the generator too. 

You won't be able to compete with the grid on cost per kwH with any kind of fuel-burning generator. Alternative energy (wind, solar) maybe - but it will take a while to see any kind of return on your investment. 

The other side of the AC equation is can you put in some kind of alternative system? Geothermal, circulate cold ground water through a heat exchanger, etc?


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## Newlife (May 27, 2012)

KC8QVO said:


> I just got the numbers for my water pump at the cabin. Can someone help me out with them?
> 
> Here's what I got:
> Dual voltage
> ...


If it is dual voltage, I'm guessing you are correct. Normally pumps/motors have a higher surge (draw/need for electricity) when starting.
The first number is likely the surge rating on the amps and the second is the amount used after the initial start up.
What I've done for my little backup AC unit is hooked it up to my little Yamaha inverter, started it on the lowest settings and allowed the compressor to kick on. Once the compressor is running, then I crank it up and let it run throughout the day at full blast to prevent it from cycling on and off. This gives me plenty of extra power to run the fridge and a couple of other devices. 
Granted, I only did this for a few days, just to see how it would work in the event of an actual emergency, but everything worked just fine without any issues (as long as I kept the on/off cycle of the compressor always on.)


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## Newlife (May 27, 2012)

nadja said:


> I am doing almost that right now. I live off the grid, and my solar system is not putting out much due to the high clouds from the monsoons. So, almost every night I have to run my gennie for about an hour or so to bring my battery bank up to snuff for the evenings. There is nothing wrong with that, although it does cost money for fuel and lots of it for the next few weeks. Also, you really need to factor in the cost of the generator and maintenance for that time
> 
> As far as how long does it have to run, it depends on several things, such as the size of your battery bank and the charge of existing batteries when you start the charging. Are you planning on living on batteries without solar just using a gennie to do the charging ? If so, you will wear out at least one generator a year


Ahh, thanks for the info. 
No, I'm not on the homestead yet, I should be moving out there in less than a year and am doing as much research as I can to minimize the pain from the hands-on learning 

My thought was to design the house for minimum power consumption and then use solar/wind to charge the batteries; but I wanted a generator backup. Actually, I'm thinking about doing something similar to what you have done.


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## Newlife (May 27, 2012)

motdaugrnds said:


> So you are all saying that if I get a generator (propane) to run my 28,000 btu air conditioner 3 months during heat of summer, it wouldn't save me any money? [Those 3 months during the heat of summer is when I would be spending $200-300 monthly for electric bill. When the air conditioner is not used, this electric bill (even during cold winter months) is less than $100 each month. So I need to find a way to save money during these heated summer months]


Sorry, my friend, but alternative types of energy aren't cheaper than the grid (normally). I'll just run some rough numbers; but feel free to add your own adjustments to make the numbers more accurate for your particular circumstances.

Hours of AC needed per day = 10 (assuming it cools enough to open windows at night.

Number of months AC is needed = 3

If you go with a gas-powered generator and get a cheap one that has enough juice to power your unit, it "might" last one season, even with the regular oil change and maintenance.
(I'm going with the cheap version rather than one that costs several thousand dollars because you mentioned costs are a factor.)

Anyway. 10 hrs a day times 7 day = 70 hrs a week. Multiply that by 4 weeks and you get 280 hrs (give or take) for the month.

If your burn rate is .25 gallons/hr (probably a low estimate) then you are looking at 70 gallons of gas a month at $3.50/gallon = $245/month just for gasoline. 
Generators need their oil changed and other maintenance done every so many hours, and with by running the generator this much, you are looking at probably once every five days for new oil.

The cheaper generators might get 200 hrs on the engine before they give up the ghost, but maybe you could get one to last all summer and only have to buy a new genny once a year (not likely with the cheapies.)

Anyway, you mentioned that your utility bill can be as much as $300/mo with the AC and drops down to around $100 without it. So, if just using AC three months a year, your additional costs are $600/year just to run your AC. (About an extra $200/month.)

Just in the cost of gasoline ($245/month), you are already spending more than the grid electricity, and you haven't even included the costs of the generator or the maintenance. If we include that cost, you will be double that easily.

I don't know what the numbers work out to for propane if you have a large tank and have it delivered, but I don't believe it is cheaper than gasoline.

So, long story short, solar, wind, generators, etc... are ways for you to generate power when/if the grid goes down, but as a way to save money, it's just not there.
If you do have medical issues and need to ensure you can survive without the grid for a short period of time, I'd get a small window AC (maybe 5,000 BTUs which is enough to cool one room) and then add a smaller, quality generator and keep them set aside for emergencies.

Honestly, the best thing you could do is find a way to reduce your electrical/power needs for cooling (extra insulation, shade, etc...)
That will give you immediate payback that lasts for years and doesn't rely on any type of fuel


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## Jim-mi (May 15, 2002)

That duo voltage refers to running the unit on 110 or 220.

The first amperage is for running on 110 . . . . surge current is way more than that.

You will note that the 220 figures are 1/2 of the 110 figures..............


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## KC8QVO (Mar 22, 2011)

Jim-mi said:


> That duo voltage refers to running the unit on 110 or 220.
> 
> The first amperage is for running on 110 . . . . surge current is way more than that.
> 
> You will note that the 220 figures are 1/2 of the 110 figures..............


So, looking at the numbers again:

9.6/4.8A
11.8/5.9A

The first line would be 9.6 amps at 110v and 4.8 amps at 220v. The second line is 11.8 amps at 110v and 5.9 amps at 220v. Does that equate to the top line being the running current and bottom line being the starting, or surge, current?


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## TnAndy (Sep 15, 2005)

KC8QVO said:


> Does that equate to the top line being the running current and bottom line being the starting, or surge, current?


Most likely.

Never seen a motor data plate with two sets of amp ratings for 120/240.

The difference in the sets is about 25%, which would be enough for a surge depending on the design. Some motors are "soft start", meaning they've done tricks with capacitors to cut the amount of surge current needed to get the ball rolling.


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## TnAndy (Sep 15, 2005)

motdaugrnds said:


> Thanks, I know I don't want the "screamers" and pricy is ok as long as I know it will do the job for us. I just found the information about the air conditioner I want a generator (propone) to run for us.
> 
> It is Kenmore model #580.75281500
> Serial #512KAZK02197
> ...


Get out your power bill. Figure out the rate you are paying NOW ( divide the Kw/Hrs into the total dollar amount ).......you'll find it's likely somewhere around 10 to 12 cents per Kw/hr.

To generate your own power with ANY KIND of generator, it will cost you 50 cents, or more, per Kw/hr.

*THERE SIMPLY IS NOTHING THAT BEAT GRID POWER FOR PRICE.*

To generate your own power will cost 5 times MORE than buying it from a power company. I know you don't believe that, yet, but it's true. You simply can't set up ANY kind of small power system and beat them because of the economy of scale....the same way you can't build a single car from scratch as cheap as Ford can crank them off an assembly line at one a minute.

There are reasons to generator your own power, such as no grid power available, or the cost of getting it to a remote site is REALLY high, or things along that line.....but if you have grid power now, you simply can not beat the price....no way.....no how.

IF you want to cut your power bill, start figuring out how to cut your use.......things like more insulation, and such. I think you said in another thread you have a mobile home. Unfortunately, those are the least energy efficient forms of housing on the planet, and you can't do much to change it.


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## Jim-mi (May 15, 2002)

In no way did I try to miss lead you in thinking a generator would substantively cut your electric bill.

I guess I was thinking, or hoping, you were more concerned with back-up for storms and such.

Many folks would benifit from having a back-up generator . . . .

You pretty much say that having that big AC is a must . . . .
OK so be it . . .
And I was trying to lead you toward getting a quality generator that can handle your very heavy electrical load.......for when the grid gets knocked down . . .for what ever reason...

There is no too ways about it . . If you want the comfort of AC . .YOU must pay for it. 
And the "grid" is currently still a *reasonable* price.....

I'll say again . . .I or others could install a system so as to have the Sun do all the work.......
But you might have a heart-attack when you see what it would cost..............



Opps . . this post is primarily intended for mortdaugrnds


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## Newlife (May 27, 2012)

Mort,
Someone did mention hydro (either this thread or another one) and that "might" be a good option if you have moving water on your property (lots of flow or lots of drop). If you do, then you "might" be able to get power cheaper. Lot's of variables on that.

However, if not, then you will save more money by reducing use rather than alternative power.


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