🚿 Water Heating Calculator
Find out how much energy, time, and electricity cost it takes to heat a given amount of water from a starting temperature to a target temperature.
What This Calculator Does
Heating water — whether for a shower, a hot tub, or a kettle — takes a predictable amount of energy based on how much water there is and how much its temperature needs to rise. This calculator estimates that energy, the time it takes with a given heater, and the rough electricity cost.
The Formula
The heat energy needed is Q = m · c · ΔT, where m is the mass of water in kilograms (1 liter of water weighs about 1 kg), c is water’s specific heat capacity (4186 J/kg·°C), and ΔT is the temperature rise. That energy is converted to kilowatt-hours, then divided by the heater’s efficiency to get the actual electrical energy drawn, which is divided by heater power to estimate time and multiplied by your electricity rate to estimate cost.
Note: This is a simplified estimate for general educational and planning purposes. It assumes no heat loss to the surroundings during heating and a constant heater efficiency; real-world results vary with insulation, ambient temperature, and equipment condition.