The month seemed to be continually cloudy either with snow which lost a couple of days to zero output or with rain which just reduced the generation down to under 1kWh for the day. The stats below don't tell the full story as the number of days below 5kWh was virtually identical between Jan 2012 and Jan 2013. Maybe days below 2kWh would show more of a difference.
Fortunately from our experience last year poor output over the winter makes very little difference to annual solar panel generation. 25% lower in January isn't the end of the world - 25% lower in the summer would be a disaster and be equivalent to losing the whole of January's output!
Edit - just seen the stats released by the Met Office. The South East had only 72% of the long term average sun for the month of Jan 2013 which ties in with our solar generation being 25% below last year.
|Jan 2013 - Our Worst Month for Solar Panel Output|