After serious thinking Roger Mills wrote :
However, it will cost considerably more to run - since it is using
electricity at peak price rather than off-peak price.

Er, well no.

The entire system switches over to off-peak, or rather just the meter
does. Two dials in the meter which record off-peak and peak consumption
the times of which are defined by a time clock, therefore any
consumption during off-peak periods will be charged at off-peak rates.

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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk