Wednesday, April 25, 2012

Generator Sizing - How big of a Generator do I need?

Generator photo from GE Home Generators' website.
You are ready to protect your home from disaster and power loss - that's great! Your kids, significant other, pets, and food in the refrigerator thank you!

But what size generator do you need for your home? This is a very common question among any homeowner considering a home generator.
In deciding generator size, you basically need to consider two important things:

  1. What is the square footage of your home?
  2. What are the power requirements for your central air conditioning system?
Finding out these two things are a great start to determining how much power your home will need in the event of a power outage. 

In order to figure out the amount of power your air conditioner uses, all you need to do is find the nameplate on the unit. That nameplate should have the BTU rating. That BTU rating will help you determine the tonnage needed for the air conditioning unit. 12,000 BTU is equal to one ton of cooling power. Now just add up the BTUs to figure out the cooling tonnage.

Once you have these two pieces of information it would be helpful to find a generator sizing guide to help you find the best generator for your needs. There are several generator sizing guides out there, feel free to try any of these:

You can also contact a licensed electrician and he will be able to give you an accurate understanding of what you need.


  1. Thanks for posting the sizing guides. I've been looking at home generators but it's hard to tell how large of a generator you need. I really appreciate the post.

    1. Hi Tarah! Thanks for your reply and I'm glad you liked the post!

  2. Also, Tarah, if you liked this, you should check out my other generator review blog!

  3. Hi there! great stuff, Thanks for sharing a very interesting and informative content, it helps me a lot, keep it up!
    The system blends in beautifully with your home's exterior and landscaping, much like your central air conditioner does. Tucked in close to your home, it has a sleek profile and a footprint that is 15% smaller than our other whole house systems.

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  4. Thanks for sharing! I just got a generator rental and I am so happy I did! My friend and I are taking a trip up to his cabin next month and I wanted to have some power.

  5. Looking for a portable genset generator for residential purpose which can give a backup for 4 hours a day. Suggest me the best generators.


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  7. This is very good information.i think it's useful advice. really nice blog. keep it up!!!

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  8. these are a must have if you live in an area with a lot of power outages or you like to throw a lot of outdoor events, it can save such headaches! It can really help to know where the best Generator Rental place is

  9. Hi, nice post. Well what can I say is that these is an interesting and very informative topic. Thanks for sharing your ideas, its not just entertaining but also gives your reader knowledge. Good blogs style too, Cheers! generator rental massachusetts

  10. What a rubberhead!

    The tonnage of the a/c and the square footage of the house have nothing to do with power requirements.

    The "boilerplate" on your outside unit (condenser) tells you the power requirements for that. Condensers typically run on 220/240 volts at 30 amps.

    And don't forget you need to determine the voltage and amp draw of the blower fan unit in your furnace. That will get added to wattage requirement of your condenser.

    I'm no pro but I know that much!

    Stick to lawnmowers Romeo before you give advice that gets you into trouble!

  11. These generac home generators and they look like they should be just right for the job. Thanks for the post.

  12. I love reading articles like yours. I solved all my back up generator problems in thirty seconds reading about how to calculate BTU's. It is sometimes embarrassing that I don't understand these things so quickly. But at least I understand more about my back up generator needs.


  13. I've been talking with my wife about getting a home generator for emergencies. We're working on getting everything else ready as well, such as emergency food and water storage and having a generator will help with the preparedness. I'll have to talk with someone about what size I'll need for my house, though, because I have no idea what I need.

  14. It's exciting to go camping without having to worry about your gas supply! We are looking to get a gas generator for camping leisure, as well as an emergency backup. I think it's important to be prepared.

  15. Thanks so much for posting a lot of this awesome content! Looking forward to checking out more.

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  16. Really very good information.If looking for new generator.

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