Depending on the ambient temperature the heat pump saves an average of 75% of the hot water bill. The conventional 150 liter geyser uses 3000 Watt to heat the water and the 250 liter geyser uses 4000 Watt.  The heat pump situated outside the house uses 530 Watt to heat 300 liters of water. Indoor heat pumps use 440Watt. Note: The heat pump automatically regulates the temperature. When the heat pump has heated the water to temperature to the desired temperature, the heat pump will switch itself off.