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What is the best emergency back-up generator for the power outage after a storm?

Tuesday, June 19, 2018

We are awaiting the arrival of hurricane Irma here in central Florida today, so it’s a good time to talk about the pros and cons of the different generator sizes and types. Any generator is better than none at all for the days or weeks it takes to restore power after a major storm. Although now is too late to buy one for the onslaught of monster Irma, having a generator ready-to-go will give you a little peace of mind about later storms during this frantic hurricane season, and the ones in years ahead. 

    The right choice depends on two factors: how comfortable you want to be and how much you want to spend. The smaller portable generators are comparatively inexpensive, but will only keep your refrigerator, a few lights, and a fan going. At the other extreme, a permanently installed standby-generator with an automatic switching mechanism can easily cost over $8,000 with installation by an electrician, but will power your whole house and turn itself on within few seconds after it senses a power outage.

Portable - 4,000 Watts and Less


  •  Low cost, $250 to $500.
  •  Comparatively light, easy to transport.
  •  Not as loud as larger portable generators.
  •  Small, easy to store.


  •  Limited capacity, but able to handle a refrigerator, several lights, and possibly a small window air conditioner at the upper end of the range.
  •  Some of the smaller portable generators only provide 120-volt power, will not operate a 240-volt appliance.

Transportable - 5,000 to 10,000 Watts


  •  Medium cost, $600 to $1,200.
  •  The larger units in this range will handle a small central air conditioner, along with lights and a refrigerator.
  •  Portable using wheels.


  •  Not easily lifted, even by two adults.
  •  Larger size takes more storage space.
  •  Noisy, unless you get one with an upgraded muffler system.

Stand-By - 8,000 to 20,000 Watts or More


  •  Will power your HVAC system, lighting, and most or all appliances in home.
  •  No set-up time, starts itself automatically when utility power fails.
  •  Powers the home through main electric panel. No extension cords.
  •  Often not as noisy as transportable generators, and can be located where operating noise is not bothersome in house.


  •  Expensive, from $8,00 to $20,000 installed.
  •  Continuous exterior weather exposure means that most last a decade or less unless scrupulously maintained. The one shown above, corroded and abandoned in place in the backyard, is an example.

Inverter - 800 to 3,000 Watts


  •  Extremely quiet compared to regular generator.
  •  Digital technology produces clean alternating current sine wave.
  •  Lightweight, easily portable.


  •  More expensive per watt than alternator generator.
  •  Most available are under 3,000 watts.

Other Considerations

  • Larger units have an electric start mechanism, necessary since a pull-start gets difficult as the horsepower goes up. Some small units also offer electric start. This also means there is a battery to maintain and occasionally replace.
  •  Stand-by generators run on LP or natural gas, which does not degrade and become unusable when stored like gasoline. Some portable generators are “duel fuel” and will run on either.
  •  The wattage shown in big numbers on the side of many portable generators is actually the “surge wattage,” which is the amount that it can produce briefly to provide the extra kick necessary to start appliances like a well pump or air conditioner. The continuous, running wattage is often much less. A typical “4000” generator will only produce about 3,300 watts of continuous power, for example. Any appliance with an electric motor will require one-and-a-half to twice the rated wattage briefly to overcome inertia and get it rotating. An average window air conditioner requires 1,200 watts to run, but 1,800 watts to start. If your home’s water is provided by a well, it is especially important to make sure you get a generator with enough surge wattage to turn on the well pump while still running other appliances. The typical 1 hp submersible pump requires 4,000 watts, for example. 
  •  It’s important to place a portable generator in an exterior location away from open windows when operating to avoid death by carbon monoxide poisoning. Running it inside a garage, even with the garage door open, is unsafe.
  •  Extension cords must be used to get power to the  lights and appliances from a portable generator. There are heavy-duty cords with multiple plugs at the end, designed to bring the power from a safe location outside the house to a distribution point inside, like the one shown below.
  •  An alternative is to “backfeed” the main electric panel so that the power can be delivered through the house wiring. But it must be done using a rated switching mechanism that makes it is impossible for electricity from the local utility and the generator to be flowing into panel at same time.  
  •  If you want to use a generator to for a small air conditioner, see our blog post “Can I run a window air conditioner on a portable generator?” There is also a short list of wattage ratings for common house appliances in the article.
  • Bigger is better, except that the large units require more maintenance and storage space. We had a 7500-watt transportable generator for years, but got tired of heaving it in and out of the truck and keeping the electric-start battery charged. Our 3300-watt generator is much quieter, along with being easier to move around and store. The extra wattage is necessary if you want to run a major appliance like a well, but we traded power for convenience. Small inverters are quiet as a sewing machine and easy for one person to carry around, while the stand-by generators are wonderful, of course, if you have the big bucks.

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Here’s links to a collection of our blog posts about HURRICANE RESISTANCE:

Should I buy a house that has hurricane flood damage?

Should I buy a house with hurricane flood damage that has been repaired?

• What can I do right now to prepare my house for a hurricane? 

Why did so many concrete block homes collapse in Mexico Beach during Hurricane Michael? 

How can I tell if the concrete block walls of my house have vertical steel and concrete reinforcement?

How much hurricane wind speed can a mobile home survive?  

Can I do my own wind mitigation inspection?  

• What is the wind mitigation inspection for homeowner's insurance? 

What are the pros and cons of concrete block versus wood frame construction? 

Is a metal roof for a mobile home approved for HUD Wind Zone 3? 

Why do so many more sinkholes open up after a hurricane?  

    Visit our ELECTRICAL and HURRICANE RESISTANCE pages for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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