I have a 19 year-old, roof mounted, 6.3 kW nominal system in two arrays (east/west facing), 40 deg. north. I've never washed the panels outside of rain and occasional hail storm "scrubbing". Replaced a failed inverter two years ago.
My peak summer output is basically the same as when installed, making 36-38 kWh on a cloudless day. I'm actually impressed my panels haven't really degraded in performance over those 19 years.
That's really impressive and well built solar system, for it to last thta long. It shows how durable quality panels are. I have a 6 month old ~3.7kW system (6 panels in total), planning on installing another 6 very soon. My house is surrounded by trees so it's been a bit of a struggle in the winter.
My latitude plus east/west arrays are a struggle anyway. On the best (presumably cloudless) December day, I got 13.98 kWh. My 12/1/2025 through 1/31/2026 average per day was 10.32 kWh.
Panels should do 30 years, easy. Inverters will usually fail after 15y, and with batteries it’s unknown what the current gen will do - 15y, maybe 20? Definitely get LFP.
I’m waiting to see what the sodium packs look like before we do Solar PV (it’s on the list but not near the top so no urgency yet).
Sodium batteries are more grid scale I believe. They require seriously high temps to operate and thats best shared in massive banks
Not just grid scale, already been used in EV’s, less temperature sensitive than Li-ion, way more charge cycles but not quite as energy dense as lithium per kg but that’s not a downside in a static installation.
What the panels' technology / manufacturer?
SolarWorld, 175 watt, polycrystalline. I don't recall any model number (paper work is filed away somewhere.) ISTR mine were made in Germany. I think at the time my system was installed, there where some 225 watt panels available, but the 175 ones were a better price point per watt.
[edit - added technology]
The SolarWorld company is no more :(
Which means your experience is irreplicable, other companies' solar panels may be crap.
Prices per watt of solar have fallen by so much over 20 years its absurd. You can probably buy the best and/or most costly residential panel on the market and still come well under whatever the median was 20 years ago. Probably well under a few standard deviations below the old median I'm guessing.