Solar investigations

We bought a house recently, and one of the nice things about the house is that it already had solar panels installed.

Even before we had completed the purchase of the house, I was already thinking and speculating how many panels it might have (based on satellite images), and how much it could generate and potentially how much we could reduce our electricity bills. From pictures taken during the house inspection, I knew the inverter was Sungrow SGK-5D 5kW inverter. I had also noticed the inverter had a WiFi dongle, which got me all excited. But of course, since we were still in house-is-not-ours-yet mode (waiting for contract exchange), I put my solar ideas aside.

Soon enough, the contracts were exchanged which got me even more excited, but of course as the saying goes - it ain't over till the fat lady sings. Once we got the keys and moved in, I set up iSolarCloud, Sungrow's web and mobile app for monitoring solar power. Of course as with most shiny new things, the enthusiasm to check how much power is being generated goes away in a few days because you start learning patterns. You see how much the system is generating and then you get used to it, especially with the changing weather conditions. You get a good feel of how much power is being generated.

So what did I learn about my solar system? Well it's a Sungrow with a 5kW inverter. That means, it generates up to a maximum of 5kW of power. The inverter also supports MPPT . MPPT (maximum power point tracking) is a technique that is used to generate maximum power output from variable power sources. In my case, this means the inverter can generate maximum power from two solar strings - or two separate arrays of solar panels that the inverter is connected to. The panels are east-west facing, which means as the day goes by, and based on cloud cover/tree shades/other reasons, the inverter will try to get the maximum power output from both the arrays.

On really good sunny days, iSolarCloud reports generation of about 45 kWh of energy. The inverter, however, does limit the maximum power output because of the 5kW output. The clipping is especially obvious on bright sunny days.

Power generation output from the panels. You can see the clipping at 5kW

One of the bigger mysteries was trying to figure out how many solar panels I actually had, especially since I don't (yet) have a ladder to climb on to the roof and examine. From Google Maps' satellite view, I could see how many panels were installed. I initially thought we had twice the number of panels we actually had (36 instead of 18). A solar panel has two halves - I thought each half was an individual solar panel, whereas it's two cells on each half which make up one panel. So with 18 panels, and each capable of 370 W power output, my system could generate a maximum of 6.6 kW of power. When I saw the inverter was a 5 kW and, based on ChatGPT overwhelmingly trying to convince me that I had 36 panels, I thought the inverter would be a severe bottleneck for the entire system. Recently, I had been talking to a few solar & battery providers to get a battery setup done and from their report I got confirmation that indeed I had 18 panels generating 6.6 kW of power.

At the end of the day 6.6 kW of power isn't too bad. I have no plans to change the solar panels any time soon, let's see how the battery setup goes. I'll post about the batteries at a later time, once I have it ready.