We had to have these fitted, (apparently it was a condition of our contract, (in the small print!), both here, at home & at our caravan/holiday home).
We are lucky that we are still in a "fix" rate until the summer at home, The caravan is on the very high variable rate.
I remember when the fitter installed ours, he said that he & his wife had their biggest argument after their own meters were installed, so his solution was to throw the monitor in a drawer!!
When ours are on display & looked at it, is saying that we are over budget, that's scary, I turn our heating down, DH keeps turning it UP...!
The actual meters are useful in that they transmit usage to supplier, (handy when we are away from the coast).