The review tested 10 kettles and shortlisted seven, assessing the visible film left on tea as well as boiling time, noise, pouring and ease of use. Its top pick was the Russell Hobbs Brita Purity Glass Kettle, whose MAXTRA PRO Limescale Expert cartridge filters water before it is heated. In the test, the tea cooled without a visible surface scum; a full kettle boiled in two minutes and 20 seconds and was quieter than several alternatives.

That performance comes with a recurring cost. Brita recommends replacing the cartridge about every four weeks, and a six-pack was priced at nearly £40 at full price in the review. The first setup also takes planning: the cartridge needs to be soaked and filtered water allowed to pass through before the kettle is used.

The comparison found that other features do not necessarily solve the same problem. Removable mesh filters can catch loose pieces of scale but may not remove dissolved minerals that contribute to the film. Glass bodies make deposits easier to see, but a clear kettle alone does not eliminate them. Models from Lakeland and KitchenAid were noted for design and usability, though the test still saw residue in tea brewed with tap water.

The review also highlighted trade-offs in specialist designs. The Graef Glass Kettle and Tea Maker offers temperature settings and a tea infuser, but tea brewing can leave stains that are difficult to clean from an electric kettle. Across the comparison, using filtered water remained the most dependable way to reduce visible scale in the cup and slow deposits inside the appliance.

For shoppers, the main distinction is between a screen that catches scale fragments and a cartridge that treats the water itself. A built-in cartridge may improve the brew, but its replacement price and schedule should be counted alongside the kettle’s purchase cost.