How much generator do I need

[Pooh Bear]

I want to get a generator. But how big.
We have one room that uses most of the electric.
I figure a 20amp breaker feeds that one room,
so 20amps x 120 volts is 2400 watts. And we don't use all that.
For the TV and computer monitors and computers and all other
associated stuff that goes with that, and a dorm fridge, and in
the winter add a 1500 watt space heater, we still haven't
tripped the breaker, so I figure that one room is staying below
that 2400 watt limit. The rest of the house is mostly lights.
We do have a kitchen fridge/freezer, and a chest freezer, both
of these are in the kitchen; gas stove and gas furnace.
The electric water heater would be switched off at the breaker.
Our central air unit is a 3 ton unit. I would like to be able to run
it if the power goes off in the summer. Also the furnace blower
in the winter. No sump pumps or well to operate.
We use electricity as sparingly as possible.
I'm figuring a 3500 watt generator would work for almost all of
it. But then there's that air conditioning unit to add to the mix.
I need an estimate of what size portable generator to get.

Thanks.

Pooh Bear

 

[David G]

There is no way you can do all that on 3000 watt, my 3 ton AC makes my 20kW snort when it kicks on.

 

[W30 Lee]

Buy as much as you can afford, then regulate the load accordingly. I'm assuming that this is an emergency and temporary situation. LE

 

[Pooh Bear]

(quoted from post at 20:26:15 12/07/15) There is no way you can do all that on 3000 watt.

This would definitely only be for emergency power situations.
We are expecting a bad winter. I want to be prepared.

OK, forget the A/C. I see a lot of 3500/4000 watt generators.
And if I don't use the space heater in this room, I'm using
900 watts max just in this room; mini fridge included.
Add to that a chest freezer and a kitchen refrigerator/freezer,
and a light on the kitchen, and you have our total electrical load.

 

[MarkB_MI]

The main consideration is the starting current for the refrigerator, freezer and A/C. If you only run one of these at a time, you might be able to get by with a 3500 watt unit. But if you go on up to 6500 watts you'll be able to run all three at once no problem. I'd say 5000 watts minimum if you don't want to be unplugging stuff.

We currently use a 6500 watt Honda through a whole-house transfer switch to run two refrigerators, a freezer, air conditioner and 3/4 hp submersible pump, plus all the usual lighting and convenience loads. We don't use the electric ovens; stovetop, dryer and boiler are all gas.

 

[John B.]

Pooh Bear, I have a 4200 watt generator and it won't pull my AC unit with everything else turned off. It will run my lights, 2
refrigerators, small deep freeze, sump pump, ceiling fans, furnace.

I am considering converting my generator over to LP. I figure if there is a bad storm the gas stations will be closed, plus LP doesn't go
bad like gasoline does and you can exchange bottles out for a full one.

By all means get a generator with Electric start with pull rope start option...

Then put an "AUTOMATIC BATTERY CHARGER" on the battery. It won't over charge the battery but will keep it charged.

These are just some of my experiences and advice to pass along.

We're already talking about getting a stationary stand-by unit in the future one big enough to pull the A/C and appliances.

 

[Dean]

No way.

KWs are kind of like money and HP. Some's good and more's better.

Buy the largest generator that you can afford. You will soon learn that it is not big enough.

Dean

 

[David G]

I would want at least a 6500 watt unit even if not running AC.

 

[Pooh Bear]

(quoted from post at 20:49:14 12/07/15) Pooh Bear, I have a 4200 watt generator and it won't pull my AC unit with everything else turned off. It will run my lights, 2
refrigerators, small deep freeze, sump pump, ceiling fans, furnace.

I am considering converting my generator over to LP. I figure if there is a bad storm the gas stations will be closed, plus LP doesn't go
bad like gasoline does and you can exchange bottles out for a full one.

By all means get a generator with Electric start with pull rope start option...

Then put an "AUTOMATIC BATTERY CHARGER" on the battery. It won't over charge the battery but will keep it charged.

These are just some of my experiences and advice to pass along.

We're already talking about getting a stationary stand-by unit in the future one big enough to pull the A/C and appliances.

I think I'm looking for at least a 5000 watt model.
Definitely with electric start.
I have thought about converting to NG, but I want to keep it
portable so I can use it elsewhere on the property.

I got my eye on a nice Champion 7500/9500 from TSC.
Can't seem to convince 'she who holds the checkbook.'

Pooh Bear

 

[dr sportster]

I don't read any plans for a tranfer switch. Don't start killing linemen.

 

[Geo-TH,In]

Consider, most generators are over rated. A 3000w Honda only has one 20a 120v outlet. Do the
math that only makes it a 2400 watt, not 3000.

Many 3500w generators have 2 120v outs, each with a 14.5 or15a breaker.

Some 3500w RV generator have only one 120v out rated at 30a.

A 3 ton AC has an extremely large lock rotor amps. I think you will need one large generator to
handle that. If you research generators, most will say not to use with motors because of the
large starting currents.

I think my 2.5 ton AC is wired on a 30 amp breaker. It's going to take a large generator to
deliver 220v and 30 amps. If for health reason you must have AC, get a small window unit and a
large RV generator.

 

[David G]

An important point was brought up, use a transfer switch.

 

[Pooh Bear]

(quoted from post at 21:27:19 12/07/15) An important point was brought up, use a transfer switch.

A transfer switch is fodder for a different question I have in mind.
I will be starting a new posting soon for the wiring.

Pooh Bear

 

[D beatty]

You need to get a chart on what everything uses and go from there. You didn't say anything about micro wave oven, toaster, coffee maker and other small things that you will use. You also have to figure power surge when frig and other large items first turn on. I use about the same things in my house as you but have well and won't use AC and I run a 8,000 run 10,000 surge generator with transfer switch.

 

[David G]

The easiest thing is to set a transfer/breaker panel right next to your existing panel, relocate circuits to this panel, and put a large feed breaker in old panel.

 

[pete black]

Personally I think most buy too much generation. Buy what you can get by somewhat comfortable on, why; 1) how often is supplied power
off? 2) When off, what is typical length of time it is off? 3) Generating one's own power is extremely expensive in kw size and fuel
cost. 4) what is fuel storage capability, such as amount, location and freshness. 5) How stored and maintenance of generator when not
needed. Do not know percentages but would venture to say in a normal year generator would not exceed 4 hours run time.

 

[David G]

I bet mine does not get more than half a dozen hours of real run time a year, plus 20 minutes of exercise every week.

 

[alg]

I had an 8000 watt portable and it would not run my 3 ton a/c.

 

[Dean]

I installed a 20 KW Kohler propane fueled whole house back up generator last year. It will run anything that I might want to operate when the power is off and was a simpler and less expensive alternative than installing a 14 KW (or smaller) unit with load shedding system due to the cost of installing the load shedding system. I wired my new pole barn built this summer to the house side of the transfer switch so that the door openers will work when power is out. I also installed a second 500 gal propane tank (free with 2500 gal prebuy) so that I will never need to buy propane anytime but in the summer.

With propane fired hot water heat, the back up generator provides great peace of mind in cold weather, as I experienced a 4+ hour power outage a couple of years ago in January when the temperature was about -20 F. Without heat, it would not take long for my heating system to freeze at such temperatures if I was not home to drain it.

Dean

 

[Geo-TH,In]

Pete,
I totally agree with you on all 5 of your good points. That's why I have two 3500w RV generators, which I use more for powering tools in a remote location. I also made an energy management system that will give my well priority over everything else. When well comes on, my refrigerator and other appliances are turned off. When well is off, a timer waits 5 minutes before it turns refrigerator on. Other appliances come on as soon as well is off.

A transfer switch cost more than some want to spend on a generator. For me, running a power cord through basement window to well is no big deal. I have well on a 12g cord, just un plug it and plug in cord. I open kitchen window and run cord on counter top to refrig and electric cooking appliances. IMHO, the well and refrigerator are the two most important things to power up. The rest you can live without for a short time.

 

[Dusty MI]

The least expensive transfer switch, and approved, is a breaker inter-lock.
My service is on my house and the generator is in a shed 100 ft away.
I bought 2 padlocks that are keyed a like and are key retention.
Then made breaker locks for each panel.

Dusty

 

[Billy Shafer]

What ever you do DON'T use the dryer plug trick.Use a transfer switch or cords. The plug can cost you more than you want to know.

 

[Butch(OH)]

Sounds like what we just did at the new place. I had contacted the electric coop about legal options for the generator and they suggested the combination meter box/breaker box with an interlocked generator feed breaker. Makes for a very neat installation and 1/3 the cost of a double throw. Just finished the installation and the coop inspected and sealed it Saturday.

 

[buickanddeere]

I am always suspicious of people who are proud of how modest they are and how little they need.

 

[D beatty]

I thought of using cords but didn't like cords laying around the floors and walking around in house at night. I didn't like the generator setting outside when its raining or snow blowing. I put in transfer switch and no cords or cracked windows and generator setting in yard in nasty weather. Generator sets inside workshop out of weather with 100 foot generator cord to house. Generator stays dry and no snow or rain to have to refuel in. Transfer switches are not all that expensive .I bought a Reliance transfer switch kit prewired 10 circuits, Amps@ 125 VAC: 60A, Amps@ 250 VAC: 30A for a little over $350.00.

 

[Pooh Bear]

(quoted from post at 10:00:09 12/08/15)
I am always suspicious of people who are proud of how modest they are and how little they need.

I'll probably regret asking, but, Why??

Didn't say I was proud of it. Wife just likes to keep the
combined electric and gas bill to around $200/month.
That's not being proud. That's being miserly frugal.

Pooh Bear

 

[jeffcat]

People will have all kinds of opinions on this one. Neighbor on one side has a 15k standby unit on the gas line. The other neighbor just got I think a 20k unit on the gas line. My back yard neighbor bought a 4500 watt that he back feeds through his 240v garage lines. I have two 3200 watt units that can just be plugged into and also have a beast of a Homelite 8000k construction site unit that will run the house. Harbor freight has a 8500K that works great. Know a couple of people that have them. They came out last year with a 13,500k monster. All of these portable units are about $100.oo per 1000 watts. My local Shop Rite has 10K units for around $600.oo My choice for a home is the 8500 unit. If you want to lift a 3 ton air compressor then just bite the bullit and go for the 13,500 unit. It should be able to pull anything you can throw at it. As I said there are all kind of opinions on this subject but you very quickly find out you can always use something bigger. By the way,,,,if you have one of the high efficiency gas heaters you do not want to scrimp on the watts. You can blow circuit boards and blower motors to the tune of $200.oo to over $1000.oo worth of damage. They must have rock solid power supplies.

 

[pete black]

When i built a new home in 2012 i installed a totally separate electrical box with circuits to particular rooms for critical loads. Generator connected via twist lock plugs. Cheaper than transfer switch and does not involve power company.

 

[D beatty]

What do you use to disconnect the power from utility company when using generator? If I would have bought another box to run everything that I do it would have cost about as much as transfer switch and I don't know if it would meet code here.

 

[buickanddeere]

Some people always pursue the quick cheap easy fix and don't realize a proper fix costs less.
I have also met some people who are proud of how humble they are.

 

[Geo-TH,In]

I like to be able to move my generator. The last thing I want is for the wind to blow exhaust towards the house. Every time I've needed the generator, I've had it in a different location. I have a piece of metal to put over my generator so when it raining or snowing, no biggie.

I don't trip over my cords, running them through the windows and putting them up on counter tops, easy solution. Works for me. Doesn't cost either. I have about 500 ft of 12 g extension cords in my truck.

 

[pete black]

It is small four circuit box with the input wired to a twist lock receptacle matched to generator. It is totally independent of main panel and in no w a y can be tied to the main panel. Four circuits to selected rooms and load. No throw over needed.

 

[John T]

Some good answers below, goes to prove my point ANYTIME AN ELECTRICAL OR LEGAL QUESTION IS ASKED YOU GET MORE ANSWERS COMMENTS AND OPINIONS THEN ANY OTHER TOPICS LOL It draws them (including Billy Bob and Bubba) out of the woodwork fer sure. Good folks here all tryin to help

John T

 

[D beatty]

So are you saying that you have double circuit the rooms and items that you want to run on the Generator ( one for generator and one for utility company).

 

[D beatty]

I have no problems with fumes with generator in workshop setting a 100ft. from house. Being as it is inside shop it is dry to refuel and I don't get soaked fueling it in rain or out in a blizzard. When electric goes out we are out for about 3 days and we have been out for a week. We are out several times a year. We are on very western edge of electric companies grid and are the last ones to get service after outing.

 

[pete black]

Yes, cost minimum, no utility involvement, no maintenance.

 

[Geo-TH,In]

Pete, that's a smart idea having a separate load center and a cord running power to it. I would have to wire things so building inspector will pass it, then make your modifications later.

 

[D beatty]

Sound good and is something to do when building a new home( easier to do at that time). For me to wire everything in my house the way you did it would cost more than transfer switch. The only things that I don't run during power outage is baseboard heat ( covered by Lp gas & wood heat), water heater, AC, and power in workshop.

 

[IA Roy]

I would not get one that would be large enough for the air conditioning. Most likely your power won't ever be off for more than a few hours, unless you live in Hurricane country. If you really need air conditioning, a motel room will be a lot more affordable for a night or 2. I have I believe, a 5000 running watt capacity unit. It is a 1999 unit with a flathead Briggs and Stratton engine. The only thing that makes it grunt is when I need to turn the water heater on for a while. Most everything else will work fine.

 

[paul]

I'm sure there is a bunch of advice below, positive and negative.

Running computers and electronics, you want a -good- generator, not a cheap one. Those electronics like to pop and sizzle and then not work
nearly as well....

Motors draw a lot of extra amps for a few milliseconds as they start up, if your generator can't supply that they will not start, so you need more
capacity that what the breaker says. Most breakers allow that heave very short motor draw.

As someone said, I would not plan to run a air conditioner on a little home cheap generator. That just won't match up well. If you want the air
conditioner, then you need to be thinking differently, think a whole house installed type of generator not a cheapie.

3500 watt will barely run what is on a 15 amp breaker, so it can work for you for emergency use, if you are careful to choose what you plug in
and turn one, one thing at a time.

Most folks get a 6000 or so and it works well for a more robust, easy to use setup.

Paul