Grohe Red Duo L-Size

The Grohe Red is the boiling-water tap from a brand most people know for mixer taps and showers, and the Duo version is the one that makes sense for a single-tap kitchen. It puts 99°C filtered water on a pair of child-safe buttons and keeps a normal hot-and-cold mixer on the lever, so one tap replaces both the kettle and your existing tap. The L-size boiler is the headline: 5.5 litres of near-boiling water, 7 litres in total, which is more usable reserve than almost anything else here and genuinely useful for filling pans.

The thing to understand before you shop is the price. Grohe's list price for the chrome L-size Duo is £2,578, but it is never sold at that. UK tap specialists list it around £1,625, which is the figure we show, putting it in mid-premium Quooker territory rather than up with the Zip. Judge it on the real £1,625, not the list.

Two caveats are worth weighing. The boil is 99°C, not a true 100°C, even though Grohe's own marketing says "100°C", so for sterilising or a proper rolling boil it falls a hair short. And the standard guarantee is two years, extended to three only if you register within three months, which is shorter than InSinkErator or Franke. The BWT filter needs changing once a year or every 600 litres. Buy the Red Duo for the big boiler, the full mixer and the German build, at its real £1,625 price rather than the list.