Always asked about them through my job - Well first of all they will at most pump out 4 litres a minute - to my mind thats about adequate. Imagine the amount of power going through the shower to warm up 4 litres instantly - Wear and tear on the unit, switches and fuses. To get more than 4 litres per minute will require stupidly larger electric cable & switches/ fuses. It is no wonder they fail usually around two years ! Best solution that's always been around is a bar shower connected to your combi boiler or if you have a hot water cylinder then a quality pump and bar shower definitely the way to go. Big difference between 3 or 4 litres per minute to around a stonking 10 litres from a bar shower ! These alternatives are more expensive however they pay for themselves over time because you are not swapping them every 2 years. Search Bogs & Taps for more information and pricing structures.