Generators are sized in watts or amps. We'll use watts here, since most appliances are conveniently sized in watts. Every generator has three wattage ratings: Maximum, Continuous, and Surge.
Continuous or Rated : The amount of power the generator can produce continuously, even for days at a time. If there's fuel in the tank, the generator will put out this much power. Only quality generators have a continuous power rating. This is sometimes referred to as a "rated" power output.
Maximum: The maximum power output of the generator for up to, say, 30 minutes. Most manufacturers list this as a half-hour rating. If you try to use the maximum for an extened period of time, you will overheat the generator and shorten the life of the machine significantly.
Surge: This term is often misunderstood. This rating is what the generator can handle for up to, say, a half-second. This is important because many appliances require a large but momentary jolt of electricity to get started. They then immediately fall back to their normal power requirements. Refrigerators, freezers, air conditioners, and any appliance with a motor will have a surge requirement. A generator with a high surge rating is desireable.
Running Watts: This term is an advertising trick that fools the customer into thinking the generator is more powerful than it is. This term appears on several discount generator brands, and refers to the maximum "steady" power output, but generally the machine can only handle this for about 5 minutes. Power output then falls off dramatically, usually about 30-50% after just 20 minutes.
Wattage Calculations
How large of a generator do I need? These handy tools will help you decide.
Or, call for free assistance.
Home
For a typical home backup situation, consider a generator with at least 2500 watts of continuous power output. This will give you enough for all the basics like a refrigerator, lights, television, microwave oven, etc. You will be able to run one major appliance at a time, plus several smaller ones.
If you have multiple refrigerators or freezers, a sump pump, or other large loads that you need to power during an outage, consider getting a generator with at least 3500 watts of continuous output. This will let you run several large appliances at once.
If you need to run extra-large appliances like central air conditioners, heat pumps, ovens, or water heaters you're going to need a home transfer switch and a 6500+ watt continuous output generator. Portable generators up to 15,000 watts are available.
RVs and Campers
For RVs, the most important consideration is usually noise. It has been our experience that most people try to buy too large of a generator for their RV. If you have a 30 AMP RV service, consider a 3,000 watt super-quiet generator like the Honda EU3000 or Yamaha EF3000iSEB. Either one will handle a big roof air conditioner, plus have power to spare for lights, power converter, battery charger, etc.
Remember, you can't use more than 30 amps because your trailer has a breaker on the main input.
The smaller Honda EU2000 is great if you don't have to run the air conditioner, and can power microwave ovens, hair dryers and more.
At Huntsville Generator, we have helped hundreds of people find the right generator for their needs, including RVs, horse and race trailers, and tent camping.