If you get annoyed by vague 'area the size of Wales' statistics then 'Without hot air' is well worth a read. Professor David Mackay has done the calculations and provides detailed models for how Britain could become sustainable in terms of energy production and consumption. 
There is lots of useful information in the book, all of it with a practical and pragmatic perspective.
Don't kid yourself that you can stop at switching your phone charger off and think you are doing your bit for the environment, for instance:
"All the energy saved in switching off your charger for one day
is used up in one second of car-driving.
The energy saved in switching off the charger for one year is
equal to the energy in a single hot bath."
Read it online here
