Calculator
Does a boiling tap really save you money versus a kettle?
The honest answer: it depends on how much you overfill the kettle, what your tariff is, and how many cups you make per day. We do the math so you can see when the tap actually wins. Sometimes it does not.
Your habits
UK average household: 8 to 12 cups per day. We assume 250 ml per cup.
UK average mid-2026: £0.27/kWh.
1.0 = exactly what you need. 1.5 = the realistic average (most people boil enough for two cups when they want one). 2.0 = the chronic overfiller.
Quooker, Qettle, Fohen sit around 10 W. Zip with sparkling can hit 35 W.
Modern kettles: 0.9. Older ones with scale: 0.75.
Your savings
Kettle is cheaper by
£10/yr
At your usage and idle draw, the kettle is the cheaper choice. You would need to boil at least 4.2 L per day for the tap to break even.
Kettle per year
£34
124 kWh
Boiling tap per year
£44
162 kWh
Kettle cost = cups × 250 ml × overfill ÷ efficiency × 0.102 kWh/L × tariff. Boiling tap cost = exact litres × 0.102 kWh/L × tariff + 24/7 idle wattage. Filter costs are not included here because they apply only to 4-in-1 taps. Use the full running cost calculator to add those.
The honest answer most reviews skip
A boiling water tap only saves money against a kettle if you boil enough regularly. The tap has a real cost the kettle does not have: idle electricity, running 24 hours a day, every day of the year. That hidden draw is what makes low-use households (one or two cups a day) lose money against a basic kettle.
The flip side: most kettle households dramatically underestimate their usage. The 1.5x overfill factor is conservative. Most people who say they boil for two cups actually boil for four. The savings are real when you account for that.
We do not factor filter cartridges or installation in this calculator. Those live in the full running cost calculator. This page is the energy-only comparison.