i kept coming back to the kitchen either too early or too late. every timer app i tried wanted me to type in a number, which was the one thing i didn't know. the physics is not hard, t = (m·c·ΔT) / (P·η). getting the inputs is the fiddly part. the wattage is printed on the bottom of the kettle and nobody ever reads it, so there are about 2700 models in the app and you can scan the barcode or point the camera at the label. starting temperature matters more than people expect: where i live tap water is around 7° in winter and 18° in summer, and that alone is half a minute on a full kettle. and a kettle bleeds heat into the room while it heats, so instead of one flat efficiency number there is a cooling term per kettle, which is why a half full kettle does not behave like a full one. stovetop is its own case. a burner gets something like 35 to 50 percent of its heat into the water, against roughly 85 for an electric kettle. the part i use every day is the cooling side. it boils, then tells you when the water has dropped to 80 for green tea or 93 for pour over, so you don't need a variable temperature kettle. before that i was pouring into a cold mug and guessing. boiling is free. the temperature presets, the steep timer and the history are paid. no account, nothing leaves the phone, the scanner is apple's vision framework. tell me where the numbers are off. the stovetop efficiencies are the ones i trust least.

Keetle

Know exactly when your kettle will boil

Know exactly when your kettle will boil