This 'solution' was posted on Yahoo! Answers. Read the warning at the very end. What more need be said?
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I have the same generator (Honda EU3000is) and had the same dilemma. Here's what I did.
You need a 30A breaker, a male extension cord terminal, a female extension cord terminal, and about 2 feet of 12/2 Romex. Don't expect to power your entire house. Find a couple of circuits that you need, and make sure they're on the same bus. All I needed was the fridge, microwave, tv, and a lighting circuit. Shut off the main breaker. Attach the 30A breaker to the bus with your desired circuits. Properly connect your romex to the male plug, then to the 30A breaker, ground and neutral buses. Use the unwired female plug to insulate the male plug when not in use. Now put clear instructions next to the panel and make sure they are followed to the letter!
1) Shut OFF main power supplyIf the generator is connected with the main supply on, you run the risk of electrocuting utility workers, and being charged with manslaughter.