Water Heating Calculator

Heating Water — Energy, Power, and Time

Raising water temperature requires thermal energy. This calculator uses the sensible heat equation to find how much energy is needed, how long a heater takes, or what power rating is required.

Formulas

Thermal energy (sensible heat):

$$Q = m \cdot c \cdot \Delta T$$

Heating time from power:

$$t = \frac{Q}{P}$$

Required power from time:

$$P = \frac{Q}{t}$$

Where $m$ is mass in kg, $c = 4186$ J/(kg·K) is the specific heat of water, $\Delta T$ is the temperature rise in °C (or K), $Q$ is energy in joules, $P$ is power in watts, and $t$ is time in seconds.

Practical Notes

This calculation assumes liquid water with no phase change. Heating ice or boiling water requires additional latent heat. Real heaters are not 100% efficient — multiply time by an efficiency factor for practical estimates.

Frequently Asked Questions

What is the specific heat of water?

4186 J/(kg·K) at room temperature. This means it takes 4186 joules to raise 1 kg of water by 1 °C.

How much energy to boil 1 liter of water from 20 °C?

About 335 kJ (1 kg × 4186 × 80 °C). Boiling from 100 °C requires additional latent heat of vaporization (~2.26 MJ/kg).

How long does a 2000 W kettle take to heat 1 kg by 80 °C?

About 167 seconds (2.8 minutes), assuming 100% efficiency: 334,880 J ÷ 2000 W ≈ 167 s.

Does this include heating ice or steam?

No. This calculator covers sensible heat only (liquid water temperature change). Phase changes need separate latent heat terms.

Can I use liters instead of kilograms?

For water near room temperature, 1 liter ≈ 1 kg, so you can use mass in kg as an approximate volume in liters.

Report

Heating Water — Energy, Power, and Time

Formulas

Practical Notes

Frequently Asked Questions

Related Tools

Recent Visits