We have had our first zero day on our energy production since the solar panels went in. It is most likely due to the 4 inches of snow on the roof  which is not very photolucent!! (radiolucent is the Xray equivalent word so I reckon that photolucent is the correct description)
However it has made me think about the year end figures so here they are:
2010 we used an average of 22 units per day electricity.
2011 we turned the very hungry computer off in April reducing our usage to approx 17 units per day saving 1200 kWh in the year.
2012 we put in our solar panels late March and reduced our average daily consumption of electricity to 12 units per day saving 1700 KWh in the year.
This at a cost of 12ish pence per KWh makes a saving of £200.00 on our bills
We have also had 2 payments from the feed in tariff of £441.43 and £85.43 = £527.00 for 9 months of generation. If we assume that the janmarch payment will be approx £80 then our FIT payment for the year will be £600 and a saving of £200 on energy means that total saving approx £800.
At £8000 for the cost of the panels it will take 10 years to get our money back (not that we are in it for the money).
Our 'middle of the night' power usage runs at somewhere around 200400watts depending on freezers and fridges doing their thing. so for 6 hours we use approx 1.8KWH. If our panels can generate at least 300 watts for 6 hours then our 'day when we are not in' power usage is covered by the panels. Even during the rainy weather in December we were getting about 200 watts generated, and averaged 2.5KWh per day although some days we generated between 0.5 and 0.8 KWH.
We have just bought a new power supply, case and UPS for our server as they lost all their magic smoke this week. The new system takes 30 watts more than the last one to run, but Mike is in the process of 'fixing' this.
While we are at it I would like to rant about the gas calculations.
If you look at our EON gas bill it says a number of items which you are then supposed to use to work out how much you need to pay. For example  a part gas bill went like this
previous

27637 estimated on 12/10/2012

Gas current

28273 read by you on 31/12/2012

Difference  636 units  with multiplier value 1.0, conversion value of 1.02264, calorific value 38.8


Converted into  7010 kWh (kilowatt / hour) used

Obviously you can all do the maths from this information can't you? It's so simple that a 12yr old with a calculator could do it!
NO it is not obvious! With the information in front of you there is no way of getting from 636 units to 7010 KWh. The essential "and then you divide by 3.6 for no apparent reason" is missing. It takes 3 levels of searching through the help file to find this missing figure. Presumably it is the conversion from wattseconds to kilowatthours but why can they not put that in each gas bill in an obvious place.