What Size Generator Do You Need

Generators are a complex subject. With wattages ranging from a few hundred to over 10,000 it can be overwhelming to figure out which one is right for you. Sure, you could dish out a few thousand dollars and get that massive stationary generator with enough power to supply the whole neighborhood. But why spend that much money if you’re only going to use it for some lights and a refrigerator? On the other hand you may buy a 3500 watt generator and realize it’s not enough to keep all your items running. I’m going to simplify the process for you and break down how many watts common household items need to run and help you figure out which generator is perfect for you.

To keep it short, I’m only going to cover some essential items in this list. There may be many more that you would like to power with a generator. Make sure to find out how many watts they use and from there it is simple math, just add all the items up to get your total required wattage. A good rule of thumb is to get a generator that is a little larger than your needs, just in case later on you want to add items. Plus, a generator really should not be ran at full load constantly. It is an engine, imagine running your car full throttle the entire way to the grocery store.

One last thing to keep in mind is starting watts vs running watts. Most items will take a little extra juice to get running and from there will balance out to a lower wattage. It’s why your generator will come with a running watts and starting watts rating. Basically the generator can handle up to the starting watts rating for a small amount of time but can not sustain that amount of power constantly. I will be including both starting and running watts in this list. That being said, lets take a look at some common household items:

  • Refrigerator – 700 running watts – 1500-2200 starting watts
  • Deep Freezer – 500 running watts – 1500 starting watts
  • Sump Pump – depending on size 800-1000 running watts – 1300-1500 starting watts
  • Well Pump 1/2 hp – 1000 running watts – 2100 starting watts
  • Electric Water Heater – 4000 running watts
  • Space Heater – 1800 running watts
  • Electric Stove with 8″ Heating Element – 2100 running watts
  • Window AC – Depending on size 1200-3300 running watts – 3600-9800 starting watts
  • Central AC – Depending on size 1500-3800 running watts – 4500-11500 starting watts
  • Box Fan – Depending on speed setting 100-400 watts

Then of course there are the basics; lightbulbs, microwaves, TV’s, etc. Most of these items will have a wattage listed on the packaging, making it very easy to figure out how much they will pull. So as an example, let’s say you want to power a space heater, electric stove, 3 60 watt lightbulbs, and a deep freezer. According to my list you’ve got:

  • 1800 + 2100 + 60 + 60 + 60 + 500 = A total of 4,520 running watts

Now the deep freezer is the only item here that has a higher starting wattage. So let’s take that 4,520 and add the 1,000 watt difference in running vs starting watts for the deep freezer. That puts us at 5,520 watts. So you’re going to need a generator with at least a 4,520 running watt rating and a 5,520 starting watt rating. And again, I’d go with a little bit extra to help the generator both last longer, and give you some cushion room in case you need to add an item or two down the road.

One last thing, and I can’t emphasize this enough. NEVER RUN A GENERATOR IN ANY ROOM IN YOUR HOUSE INCLUDING THE GARAGE! Generators run on gasoline and put off toxic fumes. Generators need to be outside, away from the house and any open windows/doors. They can and will kill you if you run them inside. No, hooking up an exhaust hose and running it under the cracked open garage door is not an acceptable option.

I hope this has helped some of you out, and again, give me a follow on Instagram/Twitter @sccoastdisasterprep to stay up to date on any reviews, articles, and tips that I write. Thanks again!

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