A geyser is actually a devise that coverts electrical energy
into heat energy for heating up water. The heating element that is inside the
geyser actually gets heated up and then in turn it heats the water in contact
with it within the geyser. There is also a thermostat device within the geyser
that cuts off the heating when the water temperature reaches the desired level.
This helps in stopping of electrical energy loss. One inlet brings in cold
water while another outlet gets rid of the hot water. When the temperature of
the water falls below the desired level the heating is again started by the
thermostat.