7 years later my solar panels still achieve maximum efficiency...

why don't you up grade your inverter? If you have 3300 watts of panel, you are potentially giving away some harvest potential! A generic design derate for DC would be ~ .77 or 77% of nameplate, which would give you an average harvest of 2,541 watts. But cool days, and edge of cloud events could shoot that up considerably. Over the course of a year, that could be a significant increase in your harvest.

My off grid system of 400 watt quite often in he winter with cool PV temps and reflection off the snow, I often see 400+ watts.

Icarus

 

Congrats burritos, I hope my panels/inverter/system will be running strong at 7 years and beyond. We're coming up on our 4 year anniversary this summer.

 

I'm still making full rated power after eight years as well. yay!

And I agree - get yourself a new inverter (maybe trade?) to take full potential of your panels!

 

you might be able to keep your old inverter and just add another small one. Perhaps run 1 string on each inverter. No way to max out that way. What brand modules and inverter do you have?

 

The inverter is likely to crap out way before the panels do, so put up a 3.3+ inverter now but keep the 2.5 inverter on the shelf. It's size will match later.

-- Goldilocks.

 

Don't know where you are buying inverters, but about $1 per watt is closer: SMA Sunnyboy Grid Tie Inverters

I think ~ 15 years is the average life expectancy of a grid tie inverter. While there are no moving parts, there are electronic parts that are subject to heat (and repeated heating and cooling) which is what really does them in. It is not a matter of if it will crap out,, but when.

Icarus

 

The failed part on any power supply due to age fatigue is almost always a capacitor. Depending on what type, could be a few cents, a dollar, or a couple tens of dollars. But it will spring back to life after replacement. Now if you melt the transformer, that's another issue.

 

SMA has an optional 15 yr warranty, Kaco has a max repair cost of 500 after their 10 yr warranty expires, I think Schneider has a 15 yrs option. Enphase is 15yrs, but that's a another story. Point is that these things are proving to be reliable, enough to get 15yrs on the warranty means 20 years of life. imho.

KACO makes 1.5 kW inverter, reasonably cost. If you don't have a combiner box and the installers ran 2 wires to the existing inverter, one string could be moved to a new inverter. May be the most cost effective way, unless you could find a buyer for the old inverter. No real big problem keeping the system as is either.

 

Burritos,
Have you seen graphs of daily output ? They follow a sine pattern when the inverter is not a limiting factor and clouds do not mess up the picture. If the top of the curve is flat it is pretty easy to eyeball how much has been cut off. It is also easy to calculate with a little calculus if that is your cup of tea. All you need is a Cos table or calculator, and to remember that the integrand of Sin(x) is Cos(x). Translate the time scale into 0 - 2*pi, find the area under the curve with its top missing, and subtract the area of that rectangle.* Representative plots from every 2 or 3 months around the year averaged would give you a pretty good idea how much production a larger inverter would supply.

* My math skills are pretty dormant. If I made any errors, anybody, please correct.

Cheers!

 

Actually there may be a more cost effective solution. Put 2 of the modules on micro inverters. That would put your kWp at 2.97 which should run on your present inverter more efficiently. Two enphase micro inverters I guess would run around $500-600 installed. Perhaps wire them before the solar meter to keep track of the total performance. Never heard of it being done, but I can't see why not. This might be a good solution for someone that wants to add a few modules to an existing system with a maxed out string inverter. The devil might be in the details, but it would be interesting to explore.

 

I'd vote for the micro-inverter. You can add them on without affecting the rest of the system. Mine work great. If one would die, the rest will still keep working.

 

Correct me if I am wrong, but how are you getting power out of a 2500 watt PV array, with a 700 watt inverter? What am I missing?

Icarus

 

Yea . . . the solar companies aren't too vocal with how much shorter the life span of inverters is, compared to the PV panels. We're running two 4kW sun power inverters ... with one inverter still able to handle another 1kW load worth of panels (4 more 225's, in our case). Now that we have the Leaf, it'll be time to start scrounging around to see if we can find some sweet deals on high efficiency 225's.

Now if it's like 2k1Toaster suggests - and it's just a cap that dies inside the inverter, THAT'd be WAY cool. That'll be worth the research!

 

My guess is that you are actually running this inverter:

Sunny Boy SB3000US 3000 Watt Grid Tie Inverter

Icarus

 

I agree that is the most likely failure. My SMA inverter contains 20 large electrolytics and IIRC, the Mouser price was ~$40 each when I checked last year.

I'd encourage the OP to figure out a way to harvest all of the electricity produced by his solar panels. It seems wasteful not to put every available kWh to use.

 

The problem is finding people who will repair them,, and take the liability for doing so. As with so many electronics, no one wants to fix them, and few will stand behind doing so.

Icarus