As @Tinuvarecently pointed out, the cheapest part of a solar system is the PV panels.

Now, my system currently has 12 * 325 W panels. I see adverts for panels rated in excess of 400 watts. The best claimed figure, available locally, that I saw in about 5 minutes googling this morning was 450 W. At less than 3 grand a panel.

So now I start wondering: What if I upgrade my panels. On a sunny day, if the panels perform as I expect, there would not be much benefit to me. My batteries are usually fully charged by 11:30, and then the system just draws enough PV to keep everything ticking over.

But on overcast days... is the maths of PV panels such that I can say that in any conditions I will get 450 (claimed output)/325 (current panels) times as much PV power?

If so, and if I can off load my current panels at a helpful price, then that might be a worthwhile upgrade.

I have though about this as well. What bothers me is that if one waits too long (years), the future panels will be more efficient and of higher capacity. 

Adding these new panels to my current, "old", panels/strings will provide no more power because as I understand it, in series, the panel that is producing the lowest current is the max current that the string can provide.  Is this correct?

One would then have to sell the "old" panels and buy all new to gain some benefit, an expensive exercise considering panels have a claimed 20yr lifespan.

Mmmmmm..I might have to get a few more now!

Yes, I'm thinking (not too hard) of replacing all 12 panels. 

Or I'd like a 3rd string, West facing. It's been suggested that I could use a timer to switch betwee the current East facing and the new West facing strings. But I'd have to find the DC components (because there's more danger of arcing) and somebody willing to do it. 

Edited December 16, 20213 yr by Bobster

i upgraded my old 355 watt panels to 540 watt panels, took a knock of nearly 25% on the price