A 10% loss per year on that site equates to over £20,000.
You don't need to get into complicated maths, to realize its worth while to get them cleaned every 26 weeks.
Hi Alex. You are right. For what the array produces, cleaning is awesome value. 
That's true, but who says it's losing 10%? How is it known? How long does it stay clean? How can it be measured?
Hi Dave. I'll try to answer your questions one at a time.
1. 10% at this point is an estimate. Based on experience from other jobs, I know certain parts of the array would have been losing more.
2. The panels under the tree line, will not be clean as the panels in full open sun. As the article states, this is the very first clean on this site, so as yet, we are unsure how long it will stay clean.
3. It can be measured by the monitoring dept at Toyota and British Gas. Both have expensive equipment to measure the performance of the array. This is not, with all due respect, a cheap residential install of a few panels. This cost millions to install. The panels would have been relatively cheap. The monitoring equipment is not. It has been monitored from day 1 until today. I will be sitting down at some point with British Gas and discussing the figures. Believe me, if they are favourable, which I believe they will be, I will be writing another article explaining the real benefits of solar panel cleaning on this specific site.
Do not underestimate these clients. They are no mugs. They are huge, huge companies who do not throw money away. They have whole departments devoted to monitoring. I cannot fool them. Their tech gives them the info, not me.
