... Option Tempo ...
There are three colours, blue (jours bleus), white (jours blancs) and red (jours rouges) which represent low rate, medium rate and high rate ... The rules for tempo are
* The tempo year starts on 1st September.
* The tempo day starts at 6am.
* There are 300 blue days, 43 white days and 22 red days per tempo year.
* The number of days of each colour is fixed each tempo year.
* Sunday is always a blue day.
* Red days can not fall on a holiday, weekend or more than 5 weekdays in a row.
... despite the increased standing charge, electricity on blue days is by far the cheapest that you can get it, and during the cheap rate on a blue day the rate is extremely low.
On white days the rate is higher than either option HC or Base, but not by much. The bad news is that on red days the cost is ... prohibitively expensive ... Of course these days are usually the coldest of the winter.
The main draw back is that you don’t know what colour the next day is until 8pm the night before.
You have a display unit that plugs into any socket in your home that picks up a signal from the supply and so the unit displays the colour with a light, both for today and the next (from 8pm) ...
http://www.thisfrenchlife.com/thisfrenchlife/2004/11/electricity_tar.html