Wednesday 4 October 2006 2.45pm
switch on both the peak and off peak water imersion heaters, sit and watch the switches, note down the time when the peak swith light goes off, and the off peak switch light comes on.
easy (if you have on and off peak imersion heater switches with lights, and lots of spare time between 10pm and about 2am).
The TfL website has links which lead eventually to environmental energy saving sites...
have you tried the Energy Saving Trust
? this website is very useful!
and they do a home energy efficiency test here