Back-feeding refers to the controversial practice of shutting off the main breaker in an electrical panel to isolate the panel from the utility grid, followed by feeding the output of a generator into a secondary circuit (for example, the clothes dryer circuit). Note that I do not recommend this practice, and specifically disavow any responsibility should you decide to do so. In fact, it very well may be illegal in your area to backfeed the service entrance panel. I received an email from a man in the UK noting that it is a felony in his country to tamper with the electrical system. My purpose here is to offer some safety tips that are applicable to any usage of a backup generator, regardless of how the user goes about connecting it. If you decide that you are going to use a generator during power outages, whether you use extension cords, a transfer switch or any other method, here is what I recommend:
Make a plan on paper detailing a safe way to use your generator. Do this when everything is normal, not during a power outage. Make a list of exactly what equipment or circuits you will need to power, equipment (such as a larger gauge extension cord, for example) you will need to do so safely, and which circuits will need to be switched off before you do anything else. Buy any equipment you will need to do the job safely, and store it in a permanent location where you can always find it when you need it. Right beside the generator would probably be a good place. Add a flashlight with fresh batteries, gloves, any tools you may need, etc. so you are not having to cobble something up or chase down needed supplies during a power outage.
Now for a very important part: make a checklist. Think about it, do the math pertaining to loads, load balancing and wire sizes, and decide upon the safest order of the steps that need to be done. Make a second checklist for returning to normal after the public power is restored.
Now, keep that checklist where you can access it every time you need to run the generator. No matter how well you know what you are doing, follow the checklist and check the steps off as you complete them. Also add notes to the checklist about anything noteworthy: problems, ideas on how to do it more safely and efficiently, etc. You should be referring to the checklist every single time you ever run the generator, making notes and revising the checklist after the event is over.
That is the safe way to do any complex task. And it is a lot easier than stumbling around, trying to decide what to do in the midst of a power outage.
Related post: How I Connect My Generator To The House