"Andy Burns" wrote in message
...
Chris Green wrote:

Andy Burns wrote:

http://www.reuk.co.uk/wordpress/solar/solar-insolation/

What I *actually* want to know is the 'average over the year' *watts*
from a panel. I could work it out backwards from the above

well it's not difficult e.g assume you live in cambridge, a 1kW panel
would give you 863kWh/year, so a 250W panel a quarter of that is
215kWh/year or 0.6kWh/day, an average 25W

But what matters to him is what happens on the worst days in winter and how
many of those you get in a row so that he doesnt get enough water moved.