Cordless jug kettle, c. 1980s onward
A steel jug with a hot plate for a floor and a clever little switch that feels for steam. Lift it off its base and there are no wires to it at all: power comes up through a round plug in the middle that fits any way round. The heater is sealed under the floor, out of the water's way.
Closes the filling hole and keeps the steam heading down the right path. A spring hinge flips it open when you press the button on the handle.
Made of Stainless-steel dome in a polypropylene rim, a silicone seal, a steel hinge pin and spring.
A lid that seals well matters to the switch: if steam leaked out round the edge, less of it would reach the steam sensor, and the kettle could keep boiling longer before it clicks off.
Est. cost to the maker $0.5–1.5
A clip-in mesh across the spout. It lets water through and holds back the flakes of scale that build up in hard-water areas.
Made of Polypropylene frame with a fine nylon or stainless-steel mesh.
Limescale is mostly calcium carbonate. Heating hard water drives out dissolved carbon dioxide, and the carbonate that the water can no longer hold settles on hot surfaces.
Est. cost to the maker $0.1–0.3
One plastic moulding that makes the rim, the spout and the handle. Inside the handle runs the steam channel down to the switch, and on top is the button that opens the lid.
Made of Polypropylene, a chromed plastic button and spring, stainless screws into brackets on the body.
Polypropylene carries heat roughly eighty times less well than stainless steel, which is a large part of why the handle stays comfortable while the jug is at boiling point.
Est. cost to the maker $1–3
The jug itself: a stainless-steel tube rolled from sheet and welded up the back, behind the handle. A window beside the handle shows the water level, and a cluster of small holes leads into the spout.
Made of Type 304 stainless steel, a laser-welded seam, a polycarbonate or copolyester window with silicone gasket, welded handle brackets.
Grade 304 stainless, often stamped 18/8, is about 18 per cent chromium and 8 per cent nickel. The chromium forms an invisible oxide film that heals itself when scratched, which is what keeps it from rusting.
Est. cost to the maker $2–5
The floor of the jug and the heater in one. A stainless plate is bonded to an aluminium spreader with a tubular element pressed into it, so the hot part never touches the water. The cut-away shows what lies underneath.
Made of Stainless-steel plate, an aluminium heat-spreader casting, a sheathed element (nichrome coil packed in magnesium-oxide powder inside a metal tube), brass cold-tail terminals, a silicone seal.
A hidden element lets a kettle boil as little as one cup: the old exposed coil had to stay covered by water. The faint horseshoe of heat tint and scale on the floor traces the element's shape underneath.
Est. cost to the maker $2–5
The brains, with no electronics in it. Steam from the boiling water runs down a tube in the handle onto a bimetal disc, which snaps over and flips the switch off. Two more discs press on the plate and cut the power if the kettle is switched on empty. In the middle is the jug's half of the round connector.
Made of Phenolic and nylon mouldings, three snap-action bimetal discs, silver contacts, steel springs, brass terminals, a silicone steam tube, an indicator light.
A bimetal disc is two metals bonded together that expand at different rates. Warmed past its set point, a domed disc snaps inside out in a fraction of a second, a jump big enough to throw a switch with a click.
Est. cost to the maker $1–3
The plastic underside of the jug, seen here from the inside. It shields the wiring and the control, and holds the jug's half of the round connector in its centre hole.
Made of Polypropylene moulding with ribs and screw bosses; the rating plate is printed or moulded on its outside.
The rating on the bottom tells you the current: 2,200 watts at 230 volts is about 9.6 amps, one of the biggest loads you can put on an ordinary socket.
Est. cost to the maker $0.5–1.5
The part that stays plugged in. It holds the other half of the round connector: a centre pin with metal rings around it, so the jug can be set down facing any way. The cord winds into a channel round the rim, and rubber feet stop it sliding.
Made of Polypropylene housing, brass and nickel-plated contacts, a three-core flexible cord with plug, rubber feet.
In Britain, when a popular TV programme ends, so many kettles go on at once that the national grid prepares extra power in advance. The effect is called TV pickup.
Est. cost to the maker $1.5–4
Prices are rough ranges of what the manufacturer pays for each part, pieced together from published teardown and bill-of-materials estimates. They vary a lot between models, years and order sizes, and they leave out assembly, software, research, shipping and profit. The drawing shows a generic device, not any particular model.