KettleSpeed & energyBest forDownside
Electric kettleFastest for a mug; auto-offMost kitchens — the defaultCounter space; a plug; can fail
Stovetop (gas / induction)Fast on a strong hobNo gadget, the whistle, the lookYou must watch it; can boil dry
Stovetop (electric coil)Slowest to boilIf it's the only optionSlow; wastes heat
Variable-temp electricSet temperaturesGreen tea, pour-overA separate, pricier decision