The amount of electricity you generate from solar panels is dependent on how many panels you install and the efficiency of these panels. You will need to do a little math to calculate the number of panels you will need. Higher-efficiency panels are often your best bet cost-wise.
Episode .1 Solar power in the UK. An in depth look at the truth and science that lies behind the madness of solar power in the United Kingdom. Sources below.
Always use non abrasive cleansers on your solar panels. An abrasive cleaner can scratch the surface of the panel and cause permanent damage and affect how well the solar panel works. There are commercial cleaning solutions to use or you can use a pool skimmer with a very soft cloth on it.