Re: Zero point energy. That's the answer.
"Unfortunately this means that Stargate-SG1, and the various spin offs, contain a number of episodes that are clearly nonsense, but we will just have to live with this and pretend not to notice :-)"
To be fair, there's a lot of SF which was based on stuff we now know to be incorrect or "cutting edge" for the time and since debunked. Just look through some old physics text books :-) Not to mention these are usually not actual scientists writing the books and even scientists get it wrong frequently when extrapolating what we think we know into the future.
Now, where's my personal jetpack, flying car, hoverboard and nuclear generated electrickery too cheap to be worth metering -)