When Do Hot Water Cylinders Heat Up?

Hot water cylinders heat up based on the type of system and your chosen settings. For many homes in New Zealand, especially those with electric systems, cylinders are set to heat water during off-peak electricity hours—usually overnight—to take advantage of cheaper rates. This is managed through the electricity meter or a built-in timer.

Gas systems and continuous flow models typically heat water on demand, but storage cylinders powered by gas can have heating cycles that occur more frequently throughout the day. Some systems have thermostats and programmable timers, allowing you to control precisely when heating occurs.

Heat pump water heaters and solar-assisted cylinders operate differently. Heat pumps generally run during the day when ambient air temperatures are higher and more efficient, while solar systems heat when sunlight is available, typically storing hot water for evening use.

Understanding when your cylinder heats up can help you manage energy use and ensure hot water availability. If you frequently run out of hot water, your heating schedule or thermostat setting may need adjustment. Most systems aim to keep the water at 60–65°C to prevent bacterial growth while maintaining efficiency. If unsure, it’s worth checking your control panel or having a licensed technician review your system to optimise its performance.