Little foot energy saving shower widget - any good?

[Scrump]

I picked up one of these water/energy saving packs at Sainsburys today:

has a "Water widget" which claims to "Save =A3100 on your utility bills". There is no justification for that figure of =A3100 the website. I've fitted it and there is no noticeable difference to the shower flow. Since I have a combi boiler I presume the water will heat up more quickly. Or will the cold sucked-in air make the water colder?

Has anyone fitted one?

Any comments?

It makes a really annoying whistling sound. The missus isn't going to like it.

[Tabby]

Useless site doesn't say what it does. If its a flow restrictor, bad idea, results in connections bursting. If its an aerator, those work.

NT

[YAPH]

^^^^^^^^^^^^^^^^^^^ ?? - explanation?

[Tabby]

Some shower outlets are designed for minimal pressure only. Add a flow restrictor and the pressure on the shower outlet goes right up, with predictable results sometimes.

NT