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Understanding energy when heating liquids

Tea, anyone? Think twice!

When you make tea, you fill your kettle with almost 1 liter of water and let it boil till it automatically switches off. Right? To heat 1 liter of water from 25°C to 100°C, you need 87 Watt-hour (Wh) of energy. You pour 150-200 ml into your cup, add the tea bag, and sip your brew. The remaining 800-850 ml of boiling water simply sits in the kettle and cools off accounting for the one largest energy losses in your kitchen.

With that 87 Wh of energy; you could have fully charged your phone from 0 to 100% seven times and used it for two weeks. Think about that the next time you take a break and scroll through your mobile phone while drinking tea. Also, take a moment to assess, does a cup of tea really need an entire litre of water? And does all that water necessarily need to be heated to 100°C ? Depending on the tea type, the best brewing temperatures range from 70°C to 90°C. Can you fathom the cumulative carbon footprint caused by tea drinking?

Take another perspective, focusing both on the volume of water and the wastage of energy: the adult resident population in Switzerland drinks 748 million liters of tea each year, i.e., almost an entire lake of tea! (Zurich's Katzensee has an average volume of 842 million liters) Let’s assume that an energy-conscious tea drinker boils close to double the amount of water needed (say 400ml instead of an entire liter). This conscious or conservative heating would also translate to losing 262 GWh of energy for nothing!  

The facts above indicate two problems signaling energy wastage:

  1. We use too much water. By heating excessive amounts of water, we waste almost four times the amount of energy we actually need.

  2. We overheat water each time to 100°C instead of heating it to the optimal brewing temperatures of between 70°C and 90°C (covering the entire range of white to black teas).

Change your approach and save energy

A slight conscious effort goes a long way to impact sustainable energy.

1.      Limit filling your kettle to the amount of water that you would consume. If you need 200ml of water, heat just that much. We would then need just 17.4 for 200ml of tea, instead of 87Wh.

2.      Heat the water precisely to the temperature required, i.e. 70-75°C for white and green tea, 80°C for yellow and oolong tea, and 90-95°C for black tea instead of 100°C each time.

According to Watson News, Nachhaltigkeit: Mit diesem Trick kannst du Energie beim Teekochen sparen (, by heating the correct amount of water, we can decrease our carbon footprint and save energy that equals:

  • the annual energy consumption of 7,200 households

  • energy used by 17,000 Tesla Model 3 cars that drive 30 kilometres a day

  • the annual production of the Wynau hydropower plant in Oberwynau (35 GWh).

Towards a better future

Ohmic heating enables instant heating to the exact temperature for the required amount of liquid. No energy waste. No waste of resources. No waste of time.

Know more about our revolutionary technology.

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