Calculator
What does a boiling tap really cost to run?
Idle power, heating energy, filter cartridges. The three real costs that compound over 10 years. Adjust the sliders to your kitchen, your tariff, your usage. The result is the number you should compare against any headline price.
Your kitchen
Quooker, Qettle and Fohen sit around 10 W. Zip HydroTap with sparkling can reach 35 W.
Family of 4 averages 4 to 6 L. Two-person household, 2 to 3 L.
UK average mid-2026 is £0.27/kWh. Check your latest bill for accuracy.
Most 4-in-1 taps need a £50 to £90 cartridge once a year.
Your running cost
Per year
£129
Per month
£10.75
Over 10 years
£1290
Heating energy uses physics: 4.186 kJ/kg/K times an 80°C delta (20°C to 100°C). Kettle comparison assumes 90% efficient electric kettle, no overfilling. Real-world kettle usage is closer to 1.5x because most people overfill. Your savings are likely greater than this calculator shows.
How we calculate it
Idle electricity is the dominant cost in any boiling water tap. The tank reheats roughly twice an hour, 24 hours a day, to keep the water at 100°C. Idle wattage times 8760 hours, divided by 1000, gives kWh per year.
Heating energy is the cost of turning cold mains water into 100°C boiling water at the spout. Physics: 4.186 kilojoules per kilogram per degree Kelvin, multiplied by 88°C delta (UK average mains 12°C to 100°C output), divided by 3600 to convert to kWh. That gives about 0.102 kWh per litre of boiling water dispensed.
Filter cartridges are an annual cost for any 4-in-1 tap with filtration. We use the average UK retail price for OEM-branded filters, not third-party cheap alternatives.
Kettle comparison assumes a 90% efficient electric kettle with no overfilling. Real-world kettle usage is typically 1.5x what households think, because everyone overfills. Your real savings against a kettle are likely greater than this calculator shows.