It happens that tim... formulated :

"Harry Bloomfield" wrote in message
news
Tim+ expressed precisely :
http://www.bbc.co.uk/news/uk-39169313

"A system error in smart meters has led to customers being quoted
thousands
of pounds for a day's usage of gas and electricity.
Confused customers posted the strange readings from their SSE smart meters
on social media, with one display showing almost £20,000 for a single
day."

Tim

The meters don't calculate the cost, the in home display does that, using
consumption and costs fed to it from the meter(s).

and even that calculated number isn't the one used by the company when
billing you

they start again from the raw figures

tim

Understood. The IHD in fact is fairly useless except as a rough guide.
They do seem fairly accurate though, as a means of assessing
instantaneous demand. The one glaringly obvious bit of data absent from
our IHD is the actual meter reading value. Were I designing them, that
would be top of my list to include..