Inverter Replaced - Power Output Throttled?

[Ben W]

I've had a 4.5kW SolarCity installation since 2009, and recently had the inverter replaced under warranty (barely). But I just noticed in the Tesla app that the power output seems to be throttled at 1.8kW. Has anyone else seen anything like this? I contacted Tesla to find out what's going on, but thought someone here might have an idea. Thanks!

 

[BrettS]

It definitely looks like the new inverter is clipping. This can happen if the inverter rating is smaller than the total output of your panels. Is the new inverter identical to your old one? Given the age I wouldn’t be surprised of it was a different model, and it seems like they may have replaced it with a lower rated inverter.

 

[DrSmile]

Maybe the strings aren't properly connected? Not sure that would do it but it seems like if one string was only connected it might look something like that?

 

[BrettS]

Maybe the strings aren't properly connected? Not sure that would do it but it seems like if one string was only connected it might look something like that?

No, that’s not the case. If only one string was connected then it would just be a normal bell curve with lower output all along the curve. Instead of being a 4.5kW solar system it would be a 2.25kW solar system.

 

[arnolddeleon]

Do you have easy access to the inverter? We need the model number and hopefully the rating.

The simplest explanation is they made a mistake and used an inverter that is too small.

 

[charlesj]

Yep, it does seem to be way smaller than 4.xxK if it clips at 1.x

 

[dancudds]

What did they replace you with? There's a 3.6kW inverter and they could have only connect to CTs to one phase.

 

[Ben W]

What did they replace you with? There's a 3.6kW inverter and they could have only connect to CTs to one phase.

Here's the label on the outside of the inverter box. It's possible they only replaced a component inside the box, so the label may no longer be accurate if they used the wrong part? Or else if they wired up only one phase instead of two, I guess that could explain it, but then it should clip at 2.0kW, not 1.8kW?

Sent an email to Tesla Energy support several days ago, no word back yet. Will try calling if they don't respond soon. Thanks again for the help!

 

[arnolddeleon]

Looks big enough.

I would check the local display and cycle through them see what it thinks it is doing and compare it with what the app thinks.

 

[CrazyRabbit]

Bet they didn’t wire the solar up correctly to the inverter

 

[Ben W]

Looks big enough.

I would check the local display and cycle through them see what it thinks it is doing and compare it with what the app thinks.

The display shows error 443, which indicates a printed circuit board fault. Rebooting the inverter causes it to work normally until the power level reaches about 1.8kW, at which point it starts erroring continuously and the green light turns yellow from then on; I'm not sure if it's even feeding any electricity to the grid after that. A Tesla tech is coming out in a few days to troubleshoot/fix it.

 

[Ben W]

Update: it looks like one of the two circuit boards inside the inverter is failing, capping the maximum load at 1.8kW. Even though my solar system overall is now technically out of warranty (by a couple months), Tesla is going to cover the replacement for me because the inverter failed so soon after installation. (It worked for about a month before failing, and was the third replacement inverter since the system was installed.)

My question now is whether to consider replacing the solar panels themselves with newer/better ones. The current panels were installed in 2009. Does anyone know, if I were to replace the old panels with higher-capacity ones in the same footprint (going from say 4.5kW to 6kW) but keeping the 4kW inverter (so I'd lose a bit of power on the sunniest summer days, but max power flow to the grid wouldn't increase), would that require re-permitting? How much of a hassle is re-permitting if it's required?

 

[charlesj]

Update: it looks like one of the two circuit boards inside the inverter is failing, capping the maximum load at 1.8kW. Even though my solar system overall is now technically out of warranty (by a couple months), Tesla is going to cover the replacement for me because the inverter failed so soon after installation. (It worked for about a month before failing, and was the third replacement inverter since the system was installed.)

My question now is whether to consider replacing the solar panels themselves with newer/better ones. The current panels were installed in 2009. Does anyone know, if I were to replace the old panels with higher-capacity ones in the same footprint (going from say 4.5kW to 6kW) but keeping the 4kW inverter (so I'd lose a bit of power on the sunniest summer days, but max power flow to the grid wouldn't increase), would that require re-permitting? How much of a hassle is re-permitting if it's required?

If you have the same inverter, same annual production of a bit higher I would think you would not have to re-permit expansion.
BUT, will the inverter handle such overload and clip which is to some degree is to your benefit as it would ramp up faster earlier and later in the day. Also, will the DC cable size handle the extra current?
My current 215 W inverter under each panel has 235W panels but the inverter company stated it could handle up to 270W panels so I could have more power each day and get to the clipping point of the inverter more often. I considered getting a few panels to experiment but cannot find panels 270 W, black and 1.8" height to match existing panel height and mounting hardware. Kyocera had them but they are out of business and no panels available.

 

[SoCal Dave]

Update: it looks like one of the two circuit boards inside the inverter is failing, capping the maximum load at 1.8kW. Even though my solar system overall is now technically out of warranty (by a couple months), Tesla is going to cover the replacement for me because the inverter failed so soon after installation. (It worked for about a month before failing, and was the third replacement inverter since the system was installed.)

My question now is whether to consider replacing the solar panels themselves with newer/better ones. The current panels were installed in 2009. Does anyone know, if I were to replace the old panels with higher-capacity ones in the same footprint (going from say 4.5kW to 6kW) but keeping the 4kW inverter (so I'd lose a bit of power on the sunniest summer days, but max power flow to the grid wouldn't increase), would that require re-permitting? How much of a hassle is re-permitting if it's required?

Seems like a lot of expense to go through for minimum gains to replace your panels. Adding new panels if you have the room would give you more bang for the buck.

Looks like you live in SB. If you ask the building department if replacing the panels needs to be permitted and inspected, they will absolutely say yes. If you did it without would you get caught? Probably not. Just depends on if an inspector is driving by or if you have a nosy Karen nearby who reports you.

If you do permit it, you will need to replace everything with Rapid Shut Down capability.

BTW, now that your inverter is out of warranty, a new 5kW inverter is only $1.5K when you need to replace it again. Should be pretty easy for an electrician to replace for you (1-2 hrs), especially if the conduit lines up.

Fronius 5.0kW Primo 5.0-1 Single-Phase Inverter

 

[Ben W]

If you have the same inverter, same annual production of a bit higher I would think you would not have to re-permit expansion.
BUT, will the inverter handle such overload and clip which is to some degree is to your benefit as it would ramp up faster earlier and later in the day. Also, will the DC cable size handle the extra current?
My current 215 W inverter under each panel has 235W panels but the inverter company stated it could handle up to 270W panels so I could have more power each day and get to the clipping point of the inverter more often. I considered getting a few panels to experiment but cannot find panels 270 W, black and 1.8" height to match existing panel height and mounting hardware. Kyocera had them but they are out of business and no panels available.

My original modules were First Solar FS-275, 75-watt panels with 10.42% efficiency. (My installation has 60 of them.) Tesla's latest panels supposedly have 21.76% efficiency, basically double what I have now(!), though the panels themselves have a different form factor so probably couldn't be a drop-in replacement. But if I could have 9kW in the same footprint, that would be pretty amazing! It would also certainly make it worthwhile to bump up the inverter, probably to 8kW. I'll ask Tesla and see what they say, or if any pieces of the current system might be reusable, or might help offset the cost of upgrading.

 

[charlesj]

My original modules were First Solar FS-275, 75-watt panels with 10.42% efficiency. (My installation has 60 of them.) Tesla's latest panels supposedly have 21.76% efficiency, basically double what I have now(!), though the panels themselves have a different form factor so probably couldn't be a drop-in replacement. But if I could have 9kW in the same footprint, that would be pretty amazing! It would also certainly make it worthwhile to bump up the inverter, probably to 8kW. I'll ask Tesla and see what they say, or if any pieces of the current system might be reusable, or might help offset the cost of upgrading.

If you are also planning an inverter upgrade, then I think you will exceed the circuit breaker capacity and may need two so then a new everything is needed, like starting over.

 

[Ben W]

If you are also planning an inverter upgrade, then I think you will exceed the circuit breaker capacity and may need two so then a new everything is needed, like starting over.

I think it's currently on a 50-amp breaker, which should be capable of handling 9.6kW continuous. The house has 400-amp service, so there's plenty of headroom. Another question is whether tax breaks / rebates would apply for an upgrade, or whether they only apply to new installs? I'll scope it out with Tesla and see if it makes sense to pursue, or if it's better to just leave it as-is and be happy.

 

[bkp_duke]

I think it's currently on a 50-amp breaker, which should be capable of handling 9.6kW continuous. The house has 400-amp service, so there's plenty of headroom. Another question is whether tax breaks / rebates would apply for an upgrade, or whether they only apply to new installs? I'll scope it out with Tesla and see if it makes sense to pursue, or if it's better to just leave it as-is and be happy.

Tax breaks / rebates / credits do apply to upgrades, at least at the federal level (I think all CA-level rebates and incentives have long since been exhausted). Federal ITC is 26% until Dec 31st, then it drops to 22% for 2021, and then it drops off entirely in 2022 (unless of course Congress extends it).

 

[charlesj]

I think it's currently on a 50-amp breaker, which should be capable of handling 9.6kW continuous. ...

That would be unusual for that 4k inverter to be on a 50A breaker.
But, I only can go on what I have and some others what they reported.
May want to double check.

 

[Ben W]

I just spoke to Tesla Energy again, and it looks like there's no way to repurpose any of my current installation toward an upgrade; they'd basically have to tear it all out and start fresh. However, it looks like there's an alternate section of my roof that's large enough to support its own 4kW installation! So instead of replacing the current 4kW installation with an 8kW one (and pay the 8kW price), it would make far more sense to just add 4kW in the secondary location, getting the same effective result for half the price. How often the simple solution eludes us.