Home improvement - Generators - By Bob Cyr, Dirfy Generators

A reader sent me this e-mail:

“I had a company come out and tell me I would need minimum 14KW(14,000 watts) standby generator, which would still be a bit undersized, yet I run my whole house with my 6,500 watt portable. He told me a 10KW would be too small, so why does my 6,500 watt generator run more than a 10KW automatic?” 

Great question! I have an easy answer. It can’t. I guess I could end the article here, and would be my shortest article, but I should add a little explanation. 

The output of a generator is determined by the kilowatts it can produce. A 6,500 watt generator can only produce about 27 amps. A 10,000 watt generator can produce about 42 amps, and it doesn’t matter if it is a portable or an automatic. 

There is a simple formula that can be used; watts divided by volts will equal amps. The generator produces 240 volts. 6,500 divided by 240 equals 27. 

However, it sure seems like a 6,500 watt does more than a 10,000 watt, and there is good reason for that. When you use your portable and have it run the whole house, you can be selective without trying to be. For example, you may run a few burners on the stove, but not the whole stove and oven, your water pump, heat, refrigerator, freezer, and air conditioner may start at different times. As a result, you have the feeling that you are running your whole house, which in a way you are. 

However, if you would have a couple of those kick on at the same time and on the same phase, it would trip your generator off. 

The National Electrical Code treats portable generators and standby generators differently. Portable generators do not have to be sized by the load it will be served. What that means, is that you could have electric heat and use a portable, it would still meet code. Of course you will probably burn out your generator fairly quickly. 

Automatic generators, on the other hand, have to be sized to the load it will serve. If your entire house is gas, such as gas stove and gas dryer, you could probably get by with a 10KW. However, if you have an electric stove, the minimum you would need is a 13KW. 

There are many options to meet this need, one of which is what is called power management, and one is called load shedding. Some manufacturers use one, and others use the other. Many companies will say these are one and the same, but they are not, there are huge differences.

It is very important to know the difference before you invest in your generator. Please contact your local generator specialist to learn more.

This article was brought to you by Bob Cyr, owner of Dirfy Generators.