Design Feedback: Adding 6 panels

[RxRCz]

Hello,
First post.
Currently on order: 8.16KW + 2 Powerwalls
Estimate offset of 101%
Currently do not own EVs but will in the future.
I assume new installs now will be getting the new Powerwall+
Would adding 6 panels make sense bringing it to 10.2KW seeing that I have the roof space?
What happens if the system is oversized for the 7.6kw inverter?

Attaching the layout.
Two unit condo. My unit is luckily the south facing one. 3 story building, no roof obstruction by trees or other buildings.

 

[jjrandorin]

In general, More PV = Better, if you expect your use of electricity to increase. If you dont have an EV now, but see yourself getting one while you are still living here, you should add the additional panels now. You wont be adding them later.

 

[garrett5688]

The incremental cost of 6 panels is probably not much relative to the whole project, so it would be worth it considering future increased usage, degradation over time, etc.

one thing to be aware of is you will have additional conduit on the roof with that new group of 4, if that is something that you care about.

 

[wjgjr]

I agree with the advice that now is the time to maximize panels as adding more will likely be more costly later, if it is possible at all.

To try and address some other items - I would not assume that the install will be the PW+ (vs PW2) as it seems that is not currently being installed in all cases - ask your advisor.

With 6 more panels, you will need to talk to your advisor about whether they are planning a single 7.6 kW inverter or adding second, 3.8 kW inverter. 10.2 kW, with mostly south-facing panels, may well require a second inverter. Since you are in MA, is there any implication to going over 10 kW (in total inverter capacity - not necessarily solar?) I recall at least one MA solar owner who had an issue with a 10 kW limit for some benefits, but that may vary by utility.

 

[Zinc_Saucier]

Since you are in MA, is there any implication to going over 10 kW (in total inverter capacity - not necessarily solar?) I recall at least one MA solar owner who had an issue with a 10 kW limit for some benefits, but that may vary by utility.

Yes, if you are over 10kW you have to apply for cap allocation for net metering, and (at least according to the Eversource website) the rates you get may be less than systems 10kW or less.

 

[darhall993]

Yes, if you are over 10kW you have to apply for cap allocation for net metering, and (at least according to the Eversource website) the rates you get may be less than systems 10kW or less.

These are all good points, a few other things to think about:

1. Always get as much PV as you can reasonably install! I added 9 more 340's to my array last fall and its really a game changer. I can run the dryer/electric oven and AC during the day and still feed extra to the battery or back to the grid
2. Keep in mind your panels/array will rarely if ever reach nameplate rating and certainly not if panels are facing more than one direction.
3. If you have alot of direct sun and no shading, you might see reduced production because of solar panels efficiency in the summer months, Does Solar Panel Temperature Coefficient Matter? | Solar.com In springtime here in Georgia my 13.8kW array (all south facing panels) produce easily up to my inverter limit of 11.4kW but when it gets over 85 degrees I barely produce 10kW

Good luck!

 

[wwhitney]

Yes, if you are over 10kW you have to apply for cap allocation for net metering, and (at least according to the Eversource website) the rates you get may be less than systems 10kW or less.

But does that go by inverter size (my expectation) or DC size?

Would adding 6 panels make sense bringing it to 10.2KW seeing that I have the roof space?
What happens if the system is oversized for the 7.6kw inverter?

10.2 kW DC on a 7.6 kW inverter is a DC/AC ratio of 1.34. That's perfectly reasonable. Not sure what the next size up inverter is, you might generate more energy with, say, a 9 kW inverter (not actually a size commercially available), but probably not enough to justify the cost of the larger inverter.

Cheers, Wayne

 

[RxRCz]

But does that go by inverter size (my expectation) or DC size?

Everything I've found example: energysage speaks to system size. Nothing specific to Inverter. So i'm going to go with DC size.


Thanks for the feedback everyone. Called Tesla and asked to go back to redesign and max out system to 10KW.

 

[Zinc_Saucier]

But does that go by inverter size (my expectation) or DC size?

Inverter size, sorry should have put that in the details. I’ve got 12.24kW DC on the roof, but limited to 9.9kW AC on the other side.

 

[adspguy]

My MA system is 12.24kW DC with a 10kW inverter with 3 powerwalls. A larger inverter wouldn't get the 1:1 net metering at least on Eversource. My system does peak out the inverter on the sunniest of days, but not too badly. It is balanced well for where I am. The best day I've seen was 80kWh.

 

[3mp_kwh]

".. things to think about:

1. Always get as much PV as you can reasonably install! I added 9 more 340's to my array last fall and its really a game changer. I can run the dryer/electric oven and AC during the day and still feed extra to the battery or back to the grid

This is the reason I went with 24KW, 2yrs ago.

Can anyone tell me if the utility (Eversource MA) can break an interconnection agreement, if you move or add panels to the NEM'd inverter? I thought I remember the inverter size, not the panels or STC KW, is what they go by. Am I OK to move panels to south face, or add up to ~1.3X the inverter size in additional panels, without their blessing? Thanks!

 

[Zinc_Saucier]

This is the reason I went with 24KW, 2yrs ago.

Can anyone tell me if the utility (Eversource MA) can break an interconnection agreement, if you move or add panels to the NEM'd inverter? I thought I remember the inverter size, not the panels or STC KW, is what they go by. Am I OK to move panels to south face, or add up to ~1.3X the inverter size in additional panels, without their blessing? Thanks!

Not sure about the answer to your overall question, but yes Eversource goes by the AC, not the DC, size.