They are! They also cost a bloody fortune for a crappy model when you do manage to find one. None of that lovely British high-tech, insta-boil, sleekly designed space age stuff here: it's all vintage 1980 two-cup Travelodge hotel room specials. For $150.
When we moved to the USA my wife was furious with me for refusing to buy her an electric kettle. It took me months to explain that I'm not spending over $100 (plus the electricity to run it) when I already have a nice old fashioned stovetop model and the landlord pays our gas bill. Water still boils at 100 degrees, and it's just as fast on the burner. (She claimed it 'tasted different' but I didn't have the heart to point out that that was more due to the different water than changing how we applied heat to it.)
Depends on how efficient the heat transfer from the gas burner to the bottom of the kettle is...
I suspect that in the domestic setting an induction stove and kettle with appropriate base would be the most efficient.
I have both gas and an electric kettle (being British in the US) and the electric kettle is significantly faster for me (with similar amounts of water) but loses out because it takes up counter space, whereas the kettle on the stove is only a nuisance when cooking large meals...
I doubt it. Even if you had perfectly efficient electrical kettle, you're starting out at about 50% overall efficiency since a lot of energy was wasted creating the electricity from heat in the first place. This is why I limited my statement to electricity generated from fossil fuels, which does cover a lot of electricity.
