Same systems are used in New Zealand with ripple or pilot control to switch on or off, fixed wired appliances like storage heaters and hotwater cylinders on a cheaper rate via a contactor in the meter box.
The kWh meter has two dials which are controlled via a timeclock or ripple control.
The difference between the tarifs used to be great, (half price for nite rate ). Unfortunately with the greed of POCO's it is hardly worth while anymore and the difference between day and night rate is less than a cent difference.
Most domestic supplies are rated at 63 or 80 Ampères, single phase at 230 Volts, for an average of 1200 to 1500 sq ft houses.
