While electric tanks get drained and refilled at night, heat pumps work all throughout the day. Once water reaches a certain level in the tank, the sensor will trigger and automatically start refilling the tank and heating the water at the same time. The tank will take 1-3 hours to refill and heat the water if it is completely drained. If people in your household currently take showers back-to-back, your tank will be required to refill and heat between showers. This is not how most people use their hot water system though. If you are concerned about the capacity, please talk to our team about the possibility of a dual-tank setup.