You must only use descaler suitable for use in plastic products. If you use a descaling agent, follow the instructions on the bottle or package to descale your kettle.
Regular descaling prolongs the life of the kettle. Kettles should be descaled regularly - at least monthly.
Contact your local or regional water board for information on the hardness of your tap water. If you use the kettle more than 5 times a day, you may have to descale it more often.
Regularly descaling your kettle will help to pro long the life of your kettle, keep the inside of the kettle clean and reduce boiling times which will then reduce energy consumption.