Do you need a temperature-control kettle? A picker by what you brew

A kettle boils water. That is all most of us ask of it, and for a lot of drinks that is exactly right. But boiling is a single temperature, and plenty of drinks want something cooler. Green tea made with boiling water tastes harsh. Filter coffee made with it can taste flat and burnt. So the real question is not "which kettle?" but "does my kettle need a dial?"

Tick the drinks you make below. The chart shows the water temperature each one likes, and tells you whether a plain kettle is enough or a variable-temperature one earns its place.

Why the temperature matters

Hot water pulls flavour out of leaves and grounds. The hotter it is, the faster and the more it pulls, and the bitter, drying parts come out along with the sweet ones. Delicate green and white teas have lots of those bitter compounds, so they like water well below boiling, around 70 to 85°C. Black tea and herbal infusions are tougher and are usually brewed at 95 to 100°C.

Coffee sits in between. The Specialty Coffee Association's brewing standard names about 93°C, give or take 3, measured where the water meets the coffee. A kettle straight off the boil is a few degrees over that, which is why many people let it rest a moment before pouring.

A plain kettle is fine for black tea and herbal teas. A dial earns its place the moment green tea or filter coffee is on the list.

The no-dial workaround

You can do without a variable-temperature kettle. Boil the water, then let it stand with the lid off. Pouring it into the cup or a jug first and then back also cools it a little. The catch is that you are guessing: a thermometer is cheap, but the cooling speed depends on the vessel, the room and the amount of water. It works for an occasional cup of green tea. It is tiresome if you do it every morning.

What a dial gives you

A variable-temperature kettle lets you pick a number, say 80°C for green tea or 93°C for coffee, and stops there. Many also have a keep-warm setting that holds the temperature for a while, which is handy when you make several cups. None of this changes how the drink tastes by magic. It just takes the guessing out, so the same cup comes out the same way each time.

If you pour water by hand over coffee, a long thin spout gives you control of the flow. That is a separate feature, called a gooseneck, and it is mostly useful for pour-over. Not every temperature kettle has one.

When to skip it

If you only drink black tea, herbal tea, instant drinks or hot chocolate, a plain kettle does the job and costs far less. If you make filter coffee with a machine, the machine heats the water itself and the kettle does not matter. And if you mostly drink strong tea with milk, hotter is usually better, not cooler.

What to look for

• Adjustable temperature in clear steps. Look for settings at least every 5°C between about 70 and 100°C, or at least presets for green tea, oolong and coffee.
• Keep-warm. Useful if you make several cups or brew in two stages.
• Size and material. Around 1 litre is plenty for one or two people; larger kettles take longer to heat a small amount. Glass and stainless steel do not hold flavours the way some plastics can. Check where the water touches the inside.
• A spout you can pour from. A thin spout helps with pour-over; a wide one is fine for tea.

Whatever you choose, descale it as the manual says, because limescale changes the taste of the water and slows heating. Tea and coffee both contain caffeine, so go easy late in the day. The picks below are examples at three sizes and prices, not reviews.