Not easy - EDF price list is here...
http://www2.savetodaysavetomorrow.com/documents/R77_02_09_v12_eco.pdf
Superficially it's anything from 5.968 pence up to 7.544 pence depending on where you live but I'm sure there will be other charges to take into consideration like a higher cost for the first several hundred units and a quarterly standing charge etc. etc.
Peccavi, October 2009
