AlanHarmon.net

I have solar panels from SUNPOWER, which has a very cool App that lets me have granular data on both my electricity usage and generation. I am an Electrical Engineer, and I love this information. Looking Back, it looks like the number of panels that I decided to but was just about perfect.

Solar Consumption and Production by Year

2020 - 14,659 kWh Produced, 17,289 kWh Used (2,629 Imported from Grid)
2021 - 14,991 kWh Produced, 15,095 kWh Used (103 kWh Imported from Grid)
2022 - 15,176 kWh Produced, 14,586 kWh Used (590 kWh exported to Grid)
2023 - 13,677 kWh Produced, 12,839 kWh Used (837 kWh exported to Grid)

Yearly Solar Panel Efficiency Loss

Theoretically, solar panel efficiency is supposted to go down over time. The efficiency loss of solar panels each year is typically measured as the degradation rate. On average, most solar panels experience an annual efficiency loss of about 0.5% to 1%. This means that each year, the panels produce slightly less electricity compared to the previous year.

High-Quality Panels: High-quality solar panels might have a lower degradation rate, around 0.3% to 0.5% per year.
Standard Panels: Standard panels generally have a degradation rate of about 0.5% to 0.8% per year.
Lower-Quality Panels: Lower-quality panels might degrade faster, at rates closer to 1% per year or slightly higher.

This gradual decline means that after 25-30 years, a solar panel might still produce around 80-90% of its original output. The exact rate can vary based on the manufacturer, materials used, and environmental conditions where the panels are installed.

My Panel Analysis

It is inconclusive how much my panels have degraded. The top years in order of pruduction were:
- 2021
14,991 - 2022
15,176 - 2020
14,659 - 2023
13,677

2023 Production and Net Grid Usage

As you can see by the below graph, July and August are by far the highest producing months. This is true because the days are close to the longest of the year, and the skies tend to be very clear (cloudless) most of the time. Even though June has the longest day (daylight) of the year, the whole month is usually cloudy - that is where the name "June Gloom" comes from. Even though June produces less electricity, it is also much cooler than July and August, so the air conditioning doesn't get used as much.

Each Year Varies Quite a Bit!

As you will see in the four complete years that I have had my SUNPOWER Solar Panel System, each year varies quite a bit in both production and consumption, due to the changing weather, and our personal habits changing.

2022 Production and Net Grid Usage

2021 Production and Net Grid Usage

2020 Production and Net Grid Usage

June 2024

I the month of June 2024 my solar panels produced 125% of my houshold usage, pumping this back into the grid and giving me an energy credit on my Southern California Edison bill.

Daily Production and Consumption June 2, 2024

The highest production for my panels is between the hour of 1:00pm and 2:00pm. Production starts before 8:00am and continues to before 8:00pm.

Current Power

The system will show you the Current Power at any given any time with my current system not producing 5.1 kW at 4:00pm.

Specific Panel Production

This is the current production data for each of my twenty-four solar panels. The panel in second from the left on the top row has the lowest production at 1.61 kWh. The bottom left hand corner is producing 1.72 kWh. The lowest is only 6.3% lower than the largest, with the average somewhere around 1.67.

If there is a significant issue with a panel, this is where I would see it, and then talk to my installer about getting the issue resolved.

Time to Clean My Solar Panels

I know that it is time to clean my panels. Last year, on July 29, 2023 I was able to get a 12% increase in production on my system. I will do this tonight, and also check it in a few weeks to see if the production decreases.

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My Solar Panel Production For the Last 4.5 Years