Power to the people

I caught an interesting program on Radio4 the other day about the people who balance the load on the National Grid (electricity supply). There's information on how they adjust the System frequency (about 50Hz) in real time to balance the system demand and total generation. If demand is greater than generation, the frequency falls while if generation is greater than demand, the frequency rises. But of course the demand for electricity varies a great deal throughout the day and night so there's a policy of Firm Frequency response (FFR) which includes Dynamic and Non-Dynamic Responses ... like turning up the output from some power stations or bringing up standby ones .... all facinating stuff!
But a very interesting idea of dealing with fluctuations in electricity demand is through dynamic demand. As we can measure the grid frequency through an ordinary electric socket we can start to switch off appliances (notably fridges & freezers which can be off for a while anyway) when the frequency dips below 50Hz and thus save bringing in expensive 'responses' such as buying some megaWatts from France. Apparently it would only cost a fiver to include this in the manufacture of a fridge and would be cost effective, according to dynamicDemand .
The best bit is that you can sit and watch the grid frequency in real time and see how good these National Grid jugglers are doing!