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  1. #1
    Join Date
    Mar 2010
    Posts
    1

    Default Prep for backup generator

    How do I estimate the electrical load for my house and what size generator I'll need to support it all, or to support 10 - 12 circuits?
    DRD

  2. #2
    Join Date
    Dec 2009
    Location
    Alpharetta, Ga
    Posts
    55

    Default Re: Prep for backup generator

    Do a load calculation. That means you add up the total load (wattage) of all the things you want on the generator. That will tell you what size generator to use.

  3. #3
    Join Date
    Aug 2007
    Posts
    612

    Default Re: Prep for backup generator

    Remember to consider the extra power required by some motors as they start up when calculating the size generator to get.

  4. #4
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Prep for backup generator

    Are you sure you want to size it for the whole house consumption?
    You might flip once you see how much that will cost.

    Generally you want to cover the necessary items like the fridge , stove, heat , some lights and plugs ---maybe 4 circuits or so.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  5. #5
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,557

    Default Re: Prep for backup generator

    I agree with Canuk. I have a 5kw that provides the necessary circuits needed during a power outage.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  6. #6
    Join Date
    Mar 2010
    Posts
    12

    Default Re: Prep for backup generator

    Check out this link to Generac sold at HD as Guardian. Open the first brochure, and the 2nd page has a great sizing sheet. That' s what we use to size them.

    http://www.generac.com/Residential/Brochures/

  7. #7
    Join Date
    Oct 2008
    Posts
    116

    Default Re: Prep for backup generator

    We have a 5000W portable generator (Generac) with a manual transfer switch setup to the house for emergencies. Basically we are running only 3 circuits on it. First is the well pump (20A x 120V x 2 pole = 4800 W when starting), second is a general kitchen circuit (electric for the stove controls, lights, outlets, etc.) and the third is for the refrigerator and a couple of outlets on the same circuit). I may add a fifth circuit of lighting in the house since we have added on. These four circuits can max out the generator even at its surge rating if the well pump kicks on at the time other things are running (especially the refrigerator).

    The other consideration is fuel source. If you have a portable gasoline powered unit, you have to take into account all the fuel you need to store. The only real exception to this is if you have a unit piped into public gas supplies or a very large LP tank.

    I know for us, when we have had substantial outages we can get by with about 1.5 gallons of gas/day running the generator 2 hours AM and 2 hours PM to keep the refrigerator cold, etc.

    Good luck.

  8. #8
    Join Date
    Aug 2007
    Posts
    6,480

    Default Re: Prep for backup generator

    Quote Originally Posted by canuk View Post
    Are you sure you want to size it for the whole house consumption?
    You might flip once you see how much that will cost.

    Generally you want to cover the necessary items like the fridge , stove, heat , some lights and plugs ---maybe 4 circuits or so.
    I second this motion (actually third, after Jack).

    You do not need your entire home powered during an outage, only necessities. You'll want heat which could be a minor as running the fan (gas furnace ) or as major as an electric furnace, depending on what you've got. Key lighting points, you won't need the entire house, patio, landscape lighting, or most exterior lighting. Stick to major traffic areas. Water is important if you're on a well. Municipal water sources don't usually suffer from outages - USUALLY, not always, just depends on your municipality and your area. Cooking - you'll want to be able to heat water and do some minor cooking, even if it's only heating canned soup. With a cooking source you can heat water for bathing and clean ups.

    Keep in mind, it's a pretty expensive endeavor to install a back up generator system to your house, both in terms of the generator capable of such a thing, as well as tapping a genny into your house systems. For less than $1000 you can get a good portable generator and run quite a number of items to keep yourself comfortable in times of extended power outage.
    Last edited by A. Spruce; 03-10-2010 at 12:45 AM.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

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