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Back up generator size needs

I would like to get a whole house back up generator for my entire home we just went through a hurricane and live on a property that has a water well so when there is no power there is also no water. I am having a hard time determining how big of a gerenerator we need.

Our home is 3300 sq feet  in addition to normal appliances we have a our own water well and pump as well as two separate central AC's a solar water pool heater, pool pump and a hybrid in home hot water heater.
How big of a back up generator do we need? What about transfer switches? 

Also what brand of generators is the best to have flexibility to run the different AC's at different times of the day? 

Thank you
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Posted 2017-09-16T23:55:59+0000  by Teresab Teresab
Since you probably not going to install the generator yourself, your local dealer can run through the calculations to find generator that will meet your needs.  Essentially you are only limited by your budget but obviously you don't want to spend more money than you need to.

If you just want a rough idea, Kohler has a sizing guide here.  Generac would be the other big name in whole house generators.
Posted 2017-09-17T01:45:00+0000  by Adam444

Hello Teresab.  Welcome to the Community!  We are glad to have you join the forum.

A few years ago I wrote a couple of posts on generators that are still just as timely today.  The first is a basic buying guide discussion of generators, and the second is specific to the standby generators that you are interested in.  You can find them here:

Generators I: Buying Guide

Generators II: Automatic Standby Generators


In deciding how big a generator you should purchase, the first thing to do is to consider what items if any that you normally use you can do without during a power outage.  Some items may only need intermittent power, and others may be omitted entirely until the mains come back on.  Generator sizing, and thus cost, comes down to 3 distinct choices.

First would be to spend enough money to replace your utility power entirely during a shutdown.

Second would be to choose specific circuits that you require, omit the rest and size the generator based on only those circuits.  This choice would use a simple transfer switch tied into specific circuits.

Third would be to prioritize high demand items so that if your power usage at any given time exceeds the generators safe output level, certain loads would be dropped until the total home demand drops enough to allow them back on.  An example would be if normally you can run the A/C units, but want to use your electric stove and clothes dryer.  While these are on the load sensors might temporarily drop out the A/C until the meals are done and the clothes are dried.  This allows full home function during a blackout while using a smaller generator than the first choice above.

These are the choices that an installer will give you when they visit your home and discuss the type and sizing of generator that will work best for you.  Home Depot offers standby home generator installation.  You can find more information by calling the number below.


Please check out the 2 posts I have listed above and let us know if you have any more questions.

Thanks, Chris


Posted 2017-09-19T14:22:09+0000  by Chris_HD_CHI
You say that these standby generators are not normal for a homeowner to install.  What kind of skills are needed to safely put one of these in my home.  What am I looking for in a handyman who may say they can do this?

Also, with the recent hurricanes in Texas and Florida, are these still available now?

Posted 2017-09-20T20:29:07+0000  by BettyAnn

Howdy BettyAnn,


I wouldn't recommend a generator install for anyone that isn't a licensed electrician. If you ask the electrician to do the main connections you could ask for some savings if you do some of the grunt work.

Depending on where you live, you are going to have to get specific gas and electrical permits to do the install to meet your local building code. This is advanced electrical work. I would recommend getting an electrician who is experienced with the installation of generators and of course get electrical and other permits needed.

You can do a few things necessary for the installation such as leveling the site or pouring the slab. If so inclined you can rent the equipment.

Perhaps speak to a tradesman first,and find out how much you can do,
he can then advise you, how to do it properly. Some of this stuff is mind boggling even to experienced electricians.

In regards to the availability, this most likely will depend on your location. This is because backup generators are usually installed before a disaster and not after until the area is safe to do so.


Happy generating,

Coach Dave

Posted 2017-09-21T17:27:54+0000  by Dave_HD_OC
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