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Boil only the water you need

Heating less surplus water can reduce the electricity used for a boil.

I commit
Miniature scene: Heating more water than the drinks need.
Heating more water than the drinks need
Miniature scene: Measuring a suitable fill for the same drinks.
Measuring a suitable fill for the same drinks
01 / Why this can help

Your scenario, drawn

Enough water for the same drinks

Enough water for the same drinksBoiling surplus water: 44.53 kWh; Boiling the amount needed: 23.98 kWh; Annual difference: -20.55 kilowatt-hours of electricityIN ONE YEARBoiling surplus water44.53 kWhBoiling the amount needed23.98 kWh044.53 kWh

Same scale, starting at zero. Change the assumptions to compare the two annual totals.

Sources and scope →
Read the values
Boiling surplus water44.53 kWh
Boiling the amount needed23.98 kWh
Annual difference-20.55 kilowatt-hours of electricity
02 / One possible next step

Before the next boil, use your mugs to measure the water needed and check the kettle’s minimum fill.

03 / Sources and scope

Documented mechanism

What the evidence supports

Heating less surplus water can reduce the electricity used for a boil. Measure what your drinks need while respecting the kettle’s minimum fill.

Boundary of the claim

The measured example concerns one kettle and one starting temperature, not an average household. Water kept for later is not automatically wasted water; this calculation covers electricity only.

What this simulation calculates

Initial electricity values are measurements of one plastic kettle heating 1 L versus 0.5 L from 10°C to 100°C. One boil per day and 365 days are editable assumptions; replace the energy values for a different device or task.

Published coefficients and calculation references

  1. Research study · Alejandro Gallego-Schmid; Harish Kumar Jeswani; Joan Manuel F. Mendoza; Adisa Azapagic · 2018

    Life cycle environmental evaluation of kettles: Recommendations for the development of eco-design regulations in the European Union

    Consulted section (original language): Supporting information, Table S1, PDF page 24 of 26; plastic kettle, 100°C rows

    Consultation: accepted manuscript and supporting information · DOI: 10.1016/j.scitotenv.2017.12.262

  2. Institutional guidance · Northern Ireland government, nidirect

    Energy efficiency tips

    Consulted section (original language): In the kitchen; kettle fill guidance

    Consultation: Webpage / full text

Avoid counting the same change twice

Sources reviewed:

Report a data issue

Other possibilities in this area

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universalizable.At home / 01

Boil only the water you need

Miniature scene: Heating more water than the drinks need. Miniature scene: Measuring a suitable fill for the same drinks.
Heating more water than the drinks needMeasuring a suitable fill for the same drinks

Why this can help

Heating less surplus water can reduce the electricity used for a boil. Measure what your drinks need while respecting the kettle’s minimum fill.

One possible next step

Before the next boil, use your mugs to measure the water needed and check the kettle’s minimum fill.

What changes the outcome

The measured example concerns one kettle and one starting temperature, not an average household. Water kept for later is not automatically wasted water; this calculation covers electricity only.

universalizable.The action / 02

Your illustrative scenario

Over one year · with the assumptions below

You

20.55 kilowatt-hours of electricity less

You + 10 friends

226.04 kilowatt-hours of electricity less

1,000 participants

20,549.5 kilowatt-hours of electricity less

These are scenarios, not measured personal or collective savings. One separate household per participant. People sharing a home count it once, not once each.

Your inputs

Electricity per boil before
122 Wh
Electricity per boil after
65.7 Wh
Changed boils per day
1
Days per year
365

Calculation of the difference: (122 − 65.7) Wh × 1 × 365 / 1000 = 20.5495 kilowatt-hours of electricity

Calculation boundaries

Active electricity for repeated kettle boils only. Keep the same useful amount of hot water and respect appliance fill limits. No water-saving, standby or life-cycle claim.

Initial electricity values are measurements of one plastic kettle heating 1 L versus 0.5 L from 10°C to 100°C. One boil per day and 365 days are editable assumptions; replace the energy values for a different device or task.

Sources and calculation references

  1. Life cycle environmental evaluation of kettles: Recommendations for the development of eco-design regulations in the European UnionAlejandro Gallego-Schmid; Harish Kumar Jeswani; Joan Manuel F. Mendoza; Adisa Azapagic · 2018
  2. Energy efficiency tipsNorthern Ireland government, nidirect

Read the method: universalizable.com/en/method/ · One sheet · print double-sided, long-edge binding

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