Adding additional solar panels

[Merrill]

I have 21 10 year old 210 solar panels on a 4000w inverter and I added 6 more 327 panels in 2016 on a 3000w inverter. I want to add another 6 panels and wonder if I can use micro inverters for the 6 new panels instead of buying and replacing one of the existing inverters.

 

[miimura]

As long as you have room in your load calcs to put an additional 20A double pole breaker in your panel, I don't see why you can't add those micros.

Edit: by load calcs I mean 20A more back-feed. I don't think you can use a smaller breaker than that, but I may be wrong.

 

[Merrill]

I wonder if it would make more sense to replace the 10 year old Sunpower 4000w inverter with a larger one.

 

[miimura]

I wonder if it would make more sense to replace the 10 year old Sunpower 4000w inverter with a larger one.

I would think replacing the 210W panels with 300+W panels and a new inverter would be easy if you could re-use the same racking.

I am seriously considering replacing my 9 year old and degraded 240W polysilicon panels with new ones, re-using the old Enphase Micro-inverters. The primary consideration is keeping the same panel frame size and 60 cell panel type so they drop in with no other changes.

 

[Merrill]

I was thinking about that possibility but the panels are working well and should last another 10 years, I do have a spot for about 6 more of the latest panels.

 

[nwdiver]

I wonder if it would make more sense to replace the 10 year old Sunpower 4000w inverter with a larger one.

Good chance. For the cost of 6 micro inverters and the trunk cable and all the other ancillary stuff you'd need you're almost at the cost of a 7.6kW SMA inverter that can handle ~11kW of solar. How does your solar play with your Powerwalls off-grid? New Rule 21 inverters are able to adjust their output so they're not just on or off.

 

[Merrill]

Have yet to go off grid so not sure yet.

 

[hayhayday]

if you have only 6 327w panels on a 3kw inverter could you just stick another 6 on there and have ~1.3 dc:ac ratio?

 

[nwdiver]

if you have only 6 327w panels on a 3kw inverter could you just stick another 6 on there and have ~1.3 dc:ac ratio?

That's a good idea. Would be SUPER-easy if you can get the voltages to roughly match. You'd lose a little on the mis-match but it would probably be worth it. Just run a second string in parallel.

 

[Merrill]

if you have only 6 327w panels on a 3kw inverter could you just stick another 6 on there and have ~1.3 dc:ac ratio?

Maybe I’m wrong on this but 6 327w panels is almost 2000w which would leave me only 1000w on that inverter and 6 more of those panels would be another 2000w. I’m I thinking correctly.

 

[nwdiver]

Maybe I’m wrong on this but 6 327w panels is almost 2000w which would leave me only 1000w on that inverter and 6 more of those panels would be another 2000w. I’m I thinking correctly.

That would be fine. I have 10.7kW on a 8kW SMA inverter. Do you have SMA? For some reason that's my recollection. Might have a 'SunPower' brand label on it.

 

[Merrill]

That would be fine. I have 10.7kW on a 8kW SMA inverter. Do you have SMA? For some reason that's my recollection. Might have a 'SunPower' brand label on it.

Yes, it is a SMA Sunnyboy.

 

[Merrill]

I did some research on inverters and it looks like you can use a 1.42% of your inverter rating to determine the total solar panel watts. So my 3000w SMA inverter should handle up to 4250 watts.