In 2005 I was lucky enough to be able to instal fourteen photovoltaic panels in the roof of my house. I say ‘in,’ because they replaced the existing 1960’s (concrete) roof tiles rather than sitting on top of them (so as to avoid the need for planning permission in a conservation area).
The panels generate direct current (DC), which is converted to alternating current (AC) using an inverter, and then fed into my electricity supply. The electricity used in this way is subtracted from my electricity bill; and the surplus is exported to the grid. The exported electricity earns me money at about the same rate as the units I pay for. Since 2007 there has also been a Government system for paying for units of electricity generated, called ROC’s (and a new system has just been introduced called FIT, for feed-in tariff).
The panels may not pay off their cost for twenty years; but they will go on generating electricity from the sun for as long as they last, and the cost of installation for future generations is likely to decrease, while the efficiency of the units is likely to increase dramatically. Already in Israel panels are being developed ten times more efficient than the present ones!
Today’s figures (October 1st) show:-
Units exported 5632 }
Units generated 11372 } both since January 2006
Each panel is rated at 200 watts, so the maximum they can possibly generate is 2.8 kilowatt hours (kwh). They have never reached quite that level – perhaps 2.3 kwh on occasion when the sun shines brightly overhead – but they work even when the day is cloudy, albeit at a reduced rate.
See current developments.