Telsa Inverter sizing

[SoCalSteve]

Hello,

I'm in the initial stages of getting the layout with Tesla. I ordered the 4.08 system and then called them up to up the number of panels to 14 so that I can get a 4.76 system. They of course didn't account that for my initial layout, but are supposedly doing it now! Anyways, when I called them, the BOM for the install is a SolarEdge 3800. This is undersized and I understand they are trying to keep costs low, but I was told that I can't upsize the inverter at an additional cost. I've read articles saying it's acceptable to undersize the inverters in order to keep the cost low, since you won't hit the peak of an undersized interver the vast majority of the time. But, if the higher output inverter is only a few hundred more...

More directly, how undersized of SolarEdge inverters have people been getting? And what would be an good inverter model for a 4.76 system (SE5000?) Thanks!

 

[nwdiver]

Hello,

I'm in the initial stages of getting the layout with Tesla. I ordered the 4.08 system and then called them up to up the number of panels to 14 so that I can get a 4.76 system. They of course didn't account that for my initial layout, but are supposedly doing it now! Anyways, when I called them, the BOM for the install is a SolarEdge 3800. This is undersized and I understand they are trying to keep costs low, but I was told that I can't upsize the inverter at an additional cost. I've read articles saying it's acceptable to undersize the inverters in order to keep the cost low, since you won't hit the peak of an undersized interver the vast majority of the time. But, if the higher output inverter is only a few hundred more...

More directly, how undersized of SolarEdge inverters have people been getting? And what would be an good inverter model for a 4.76 system (SE5000?) Thanks!

Keep in mind that '4.76kW' is the STC rating. Perfect conditions that are almost never achieved in the real world. I have a 5.6kW system on a 3.8kW inverter. I would normally use a 5kW inverter for 5.6kW of panels but this system was expanded about a year after it was installed. Even being oversized by ~50% 'clipping' losses this month were < 3%. 4.76kW on a 3.8kW inverter is ~perfect.

See for yourself. This inverter only clips String A so the deference between A and B is the lost production so far this year. I estimate ~250kWh lost from (5864+250) for ~4%. So far in July it's < 3%. And this is oversized by 50%. ~25% would see almost no clipping losses.

 

[SoCalSteve]

Thanks for your very thorough reply nwdiver! Sounds like I don't have much to worry about.

 

[mstgkillr]

Tesla designed my 17 kW system with a SE10000H-US and SE7600H-US, so it appears that my inverters were slightly oversized at 17.6 kW for 17 kW worth of panels. Is this going to be a problem?

The SE10000H-US will have 28 panels (9.52 kW)
The SE7600H-US will have 22 panels (7.48 kW)

 

[DrSmile]

If you have any shading at all your inverter size is still fine. 1.2x over paneling is pretty standard, the only time I would upsize the inverter is if the panels are premium, true South and 100% unshaded. Even then 1.1x over paneling works well in that scenario.