Power Move- What is the point?

Could not agree more with TonyC there is a big clue in the name. The purpose of the scheme is to encourage people not to turn on devices all at the same time as everyone else thus reducing the maximum demand on the grid which will mainly occur between 4 and 7 pm. In order to give an incentive they will give you a financial reward that reflects how much you are helping.

In my case we have an all electric house which has a heat pump and a high level of insulation. All I have to do is raise the temperature by 1 degree by 4 pm and then shut down the heating, the house will only lose about 2 degrees in 12 hours as it is so well insulated. 
we are heavy users as not only do we have all electric heating but also an electric car which we do not charge in the  the 4 to 7 window. Typically our consumption in the window is in the order of 5% as a result.

i would also fully endorse the use of monitoring plug sockets, you can move them from location to location and you may be surprised at the results. For example, we use more electrical energy on the TV ( a flat screen modern OLED type) in a week than we do using our washing machine and tumble drier a week and they are run about every other day. The TV uses very little per hour but it is on for many more hours than the Washing machine and tumble drier.

every household will be different, but by using these monitoring devices you can at least know what is worth worrying about and/or justify replacing things with more energy efficient items.

one other thing I have used these for is setting a schedule that turns off things late at night, in case you forget. Especially things like a light in the loft or in the garage which are all too easy to forget about as they are not usually visible when the loft hatch or garage door is closed.

Being a S.O.G. (Sad old git) as my offspring refer to me I have measured all our devices and pulled together a lot of data to identify phantom loads etc.

A man needs a hobby! I can bore for hours on the subject.