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Posts: 1
Reply with quote  #1 

I have a SolarEdge system that was designed for 7.32 kWp, which was installed at the end of 2015. I never go up on my roof, as I have a very tall house, but I can see my panels from a distant and they appear a little dusty. It got me thinking on whether I needed to clean them or not. I decided to look at numbers before doing anything. I was trying to figure out the best way to compare apples-to-apples over the past several years, so I decided to download daily power generation for every day in July of 2016, 2017, 2018 and 2019. I then found a site that calculated the number of minutes of daylight there was for every day involved, per my latitude/longitude. I then divided the power generated per day and divided it by the minutes of daylight, giving me the average Watt-hours per minute for the day. I then took the best five days of July from each of the years to compare. I figure, July is usually clear and hot, but there is very little variation between the top five days. Here is my results:

  • 2016: Average of 48.51 Wh/minute of daylight
  • 2017: Average of 47.37 Wh/minute of daylight
  • 2018: Average of 45.52 Wh/minute of daylight
  • 2019: Average of 44.25 Wh/minute of daylight
Another way to look at this is the average Wh/minute of daylight dropped 2.34% between 2017 and 2016, 3.91% between 2018 and 2017, and 2.79% between 2019 and 2018. I find it odd that there was a larger drop between 2017 and 2016 than in other years. The overall drop from 2019 and 2016 is 8.78%

My question is, is this within the normal drop in efficiency per year or could it be due to the panels being cleaned? My wife doesn't want me to climb up there to clean the panels, so I'd have to hire someone to do so. I've looked around to see what it would cost to have the 24 panels cleaned and have been quoted $150. Based on a cost of $0.1435/KWh, I'd need to generate an additional megawatt to pay for the cleaning. Below is my MegaWatt production per year for the first three full years:

  • 2016: 12.132 MWh
  • 2017: 11.910 MWh
  • 2018: 11.710 MWh

The drop is far less than a megawatt/hour of difference, therefore, I'm thinking that paying someone to clean my panels would not be a valuable expenditure. I know I could clean it for much less, but my wife doesn't want me to go up there (it's a bit over 20 feet from the eaves to the ground).

Any advice?


Posts: 28
Reply with quote  #2 
Have you considered counseling? Divorce seems a bit of a drastic step to resolve your problem.[wink]

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Posts: 3,063
Reply with quote  #3 
Pray for a storm...

Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay

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Posts: 52
Reply with quote  #4 
Have your trees grown 2.34 % in that same amount of time?

I just did some solar trimming on my yard. I have a ground based system and I clean them monthly maybe.

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