I highly doubt that. A fuel-powered generator works by combustion, by making air oxygen and carbon in the fuel react to produce CO₂, harvesting the (heat) energy released by that exothermic reaction.
That's why it produces the toxic CO₂ as well as using up oxygen, both of which is very dangerous in enclosed areas.
That's a basic operating principle unrelated to efficiency, as the CO₂ is not a byproduct.
if the game you purchase can't be played without an internet connection, either always online or a once-in-a-while check in, but the game you pirate can always be played regardless of the status of your internet connection . . . one of those is clearly the better service
for example, if my internet connection is up, I'll play an MMO. when it goes out, I'd like to play Skyrim, but oops, I haven't loaded the game in the last 30 days and now it wants to check in with the Steam server . . . but it can't because the internet is out. so i never get to play the game i bought - what good did it do me to purchase a legit version of Skyrim?