When prepping for generator power, be aware that they de-rate the posted power output!
When you buy a 5700 watt generator, you should be able to load it to 5700 watts right? WRONG!
Here is a yellow 5700 watt generator:
As you can see it is a good brand, and it helps with our homeless meals every month. It has a sticker rating of 5700 watts, but it's output fusing is set at 4800 watts!
See that here:
We have 120 volts fused to 20 amps on 2 plugs.
The way to calculate power is as easy as as pie...P=I( amps) x E(volts). This leaves us with: 120 volts*20 amps=2400 watts per plug. With 2 plugs it totals 4800 watts, added together! The 240 volt side has the same power levels, if you select that output instead.
A good rule of thumb is that the continuous power rating on all generators is about 25% less than the sticker rating. This will vary some, but it is always close! If it's a lot less than this, go elsewhere; because a big rating liar usually makes a poor product!!!!!
So de-rate these advertised values, when selecting a generator for homestead or emergency power use!
The other trade off is the higher the rating, the more gasoline it consumes when used. The larger units are harder to start, due to engine size! That's why large generators usually have a large tank, and an electric starter.
It is usually best to get a larger unit, because it is better to run the generator under a lighter load. Loads to the maximum will reduce life expectancy. Use good quality cords, and shorter is better!
One last consideration, fluids...use synthetic oil, and change it on schedule. Always use non alcohol gasoline, and run stabilized gas in every generator. They Will be stored...and this ensures safe level of gasoline quality!
Good information thanks.
I got bit myself when I took a 4000 watt generator out to the homestead to run my mig welder. Since it runs off of a normal outlet, it draws less than 2400 watts. I knew that the output would be about 3000 watts, so I was 'fine'. But I forgot there are 2 outlets that share that wattage! And the 1500 watts wouldn't carry the welder....🤬😭🤮👎
I was mad at ME, because I know better!!!!😭👎
So this may be a little reminder for me too. 🤕😁
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A bit tangential, but always check whether the ratings on any power tool, engine, electronic device, or appliance are peak rating or continuous rating, too.
Nope that's spot on. In electrical power there is a term called RMS (root mean squared) best expressed of as continuous or average power. This is the value to focus upon. RMS power is .707 times peak power, which is where the power deration comes from; generators are rated in peak power. It is accurate, but deliberately misleading! Most appliances are RMS power rated, except for amplifiers; they are usually rated in peak power, and suffer the same power deration.
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Good info. We just got a home generator not long ago. Still waiting to be hooked up. Be interesting to see if it's the same peak vs. continuous rating.
It will be. Take care if you power your house directly. If you do, disconnect from the main to avoid back feeding the lines. It is a safety issue for the linemen, but will also reduce your generator output by trying to run your neighbor's freezer etc.
Hollar if you have problems. If you plug it in where the dryer connects, and turn off your main breaker; that dryer breaker will act as a temporary main.
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