I would take issue with the economics of the Buckingham Palace 'tongue in cheek' wind turbine (news last week). The indication is that it can pay for itself in 15 to 20 years by lowering energy costs.
My calculations indicate that to completely pay for the device in 20 years - assuming a £30,000 cost including foundations, planning consent, electrical connections and controls, but not standby power - at a competitive 6% interest rate would require a monthly payment in the order of £215.
Assuming a generous 30% efciency, monthly generation would be 1,320KWh, giving a cost of over 16p per KWh. Not much of a lowering of cost!
Derek Limbert (F), 16 Hutchinngs Road, Knotty Green, Beaconseld, Bucks, HP9 2BB