Electric Storage Hot Water Units are generally only installed these days to replace existing units or where there is no available gas or there are other installation limitations.

Compared to gas their running cost are significantly higher.

There is a small resurgance back towards them by customers who have large solar panel banks and are looking to use there excess power production.

Rest assured if you're replacing an existing unit, these units run trouble free for their effective life and if your replace the sacraficial anode periodically that should be years beyond the warranty period.