How do I choose the right size generator?

We have online sizing programs that can help you figure out what size generator to purchase. We also recommend you contact a local installer to go over transfer switch options, generator placement, fuel line installation, and any required permits or inspections.

Make a list of all the areas of your home you want to back up with the generator, this is going to help you decide if you want to back up your whole house or just a few individual circuits.  Number the items on your list by their importance.  Example #1 might be the air conditioner or heat, #2 might be sump pumps or well pump, #3 might be refrigerator/freezer...Use the manufactures sizing tools to figure out what size generator you need for both whole house and emergency circuits you have a size range to shop within...Next is choosing a transfer switch and selecting a fuel.

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Visitor Comments

  1. Comment #1 (Posted by Anonymous)
    right size - This would be a good place to start:
  2. Comment #2 (Posted by chip legein )
    hello ! What quiet gen would I need for: 1.well pump 220vts/2. boiler 220vts/3.fridge 110vts/4.stove 220vts/5.1light cir 2ndflr/6. 1light cir 1st flr thanks & who installs?
  3. Comment #3 (Posted by H B Heft )
    1,100 sq ft 2br 2bath all elec appliances 1 person Answer: Generac Sizing Calculator Briggs & Stratton Sizing Calculator Kohler Sizing Calculator
  4. Comment #4 (Posted by TOM )
    Need replacement for onan 7.5 hdkaj in Motor home do you have any suggestions. ANSWER: 7.5HDKAJ for more infromation about this generator you can call Del at 928-453-4494 x210
  5. Comment #5 (Posted by RUSS )
    I need a stand by gen to replace an old gas one. 12kw 208V 3 phase.
  6. Comment #6 (Posted by Dale Sibley )
    I have a home that is approximately 1200 sq. ft. with central air/heat, 2 refrigerators, one freezer, electric range, usual lighting, 2 TVs, an outside building, 700 sq. ft. with a window type ac, 2 computers, 3 printers and phones that go through my computer, misc. outside lighting(front and rear). what size generator would you recommend for this set-up. Thanks. Answer: Depending on the size of the A/C-heat system, I would estimate a 14-17 kW. What size breaker powers you’re A/C?

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Last Updated
6th of April, 2011

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