The interlock may be a viable option but IMO it has flaws.
1- you have to be at the house in order to activate it.
2- how do you know when the street power has been restored.
Personally, I would spend the extra money and set the system up through a suitable Automatic Transfer Switch. Why !
1- you don't have to be at the house in order for it to work
2- when the ATS senses that street power has been restored it will shut the generator down and swap the load back to the street power.
3- I certainly don't want to have to climb out of bed at 1:00 AM on some cold winter night in the middle of a northeaster, pull my generator out into the driveway, start it up, go throw a bunch of breakers off , go plug the generator in, and then go turn the breakers back on, go crawl back into bed, lay there for the next few hours and wonder if the street power has been restored yet so that I can go back out into the stormy weather to reverse the procedure and put it away.
Nope not me !! When I feel flush enough to spend the money on installing a standby generator for our house it will be a suitable unit, large enough to power ALL the necessities, required luxury's, with room to spare for future growth, LP fired and fully automatic. In the long run, the added expense( and it's not like your going to have to re mortgage the house) will be well worth the comfort, peace of mind, ease of use.
Do it Once, Do it Right. That's my 2 cents worth
