Adding off-grid panels and batteries to existing grid-tied system

[Ampster]

I can go to the better ToU Prime rate which drops off peak from 25 to 15 cents per KWH

What does your inverter have to do with your rate plan from SCE? Are you on an EV plan? I have been away from SCE rate plans for a couple of years so I may be out of touch. My other rate is commercial for house account at an apartment.

 

[GXMnow]

To get the SCE ToU Prime D rate plan, you must have either a Plug In Electric Car, an approved heat pump system, or a home storage battery. I don't have a heat pump and my hybrid car is not a plug in so... To get on the "Prime" plan, I could use my home storage battery. I did ask SCE what info I would need to provide them, and if it needs an inspection etc. but the girl couldn't answer. I asked if there was a minimum amount of storage, and she said no. I may be able to just send them a PDF of my invoice for the XW inverter.

With the rate difference, it looks like I could certainly save a bit more money to help pay for the battery and XW inverter, but is it worth the hassle to deal with SCE? My next car will likely be plug in and qualify. My C-Max is 7 years old with 180,000 miles on it. But it still drives great, so I am not in a huge hurry for a new car.

 

[apachexmd]

I am on NEM 2.0 with those Non Bypassable Charges. Last year i got a big refund from Sonoma Clean Power which covered my minumums and my NBCs. SCP is reducing that but still paying more for excess and charging less for consumption. Perhaps you are also in one of the Bay Area CCAs?

Yes I am with Peninsula Clean Energy CCA which serves San Mateo County.

They reference your inverter which is how they limit your production. I have 5.7 kW of panels on mine and that was not a problem. I will look at my NEM agreement and try to find the 1kW additional clause.

I found the section where the application calculated my estimated generation and estimated usage. But I can not see any verbage stating "thou shall not generate more than this amount." See a snip of my NEM agreement attached.

Yes, I am able to set voltages from 48 to 59 volts with similar flexibility at the bottom. Right now with my new LFP pack I am going to only 3.42 per cell or 54.8 for the pack. Are you considering a LFP or NMC pack? It makes no difference to the Skybox. Until last month i was running a NMC pack of Nissan Leaf modules.
I have not yet figured out how to get my Orion BMS to talk over the CANBUS to my Skybox but that is not an issue. I do have a contactor that will cut out the pack if somehow the Skybox misses an event. So far that has not happened.

Great to know! LFP packs is what I'm thinking about. But realistically I was going to use whatever I can find at a good price.

I have begun charging during the day to try to reduce my NBCs which are only a $0.2 adder to my rate. I haven't done the math either. However even with my new pack I am not sure I want to add the additional cycling of it by charging my EVs. It is also inefficient in terms of the DC to AC to DC conversions. The trick has been to charge the EVs at a rate that does not exceed my solar production. That is facilitated by the flexibility of my Clipper Creek EVSE which I can vary the current draw on the fly. This is still a work in progress but for now half of my charging is from solar, after my Skybox batteries are topped off by solar and half at Super Off Peak rates.
My True Up is in February and this is the time of the year that my production starts dropping and the big variable is my EV charging. I do have to put some numbers to this.

This is interesting and something for me to keep in mind if I ever get knocked off NEM1. Part of the motivation to go have the second solar array be DC coupled instead of expanding my current array, is to avoid touching my current NEM agreement. Any changes will automatically bump me into NEM2 and likely take me off of my E-6 TOU rate plan.

My main load panel and my critical loads panel are next to each other with wiring gutters top and bottom so I can move circuits easily. The only loads not on my critical loads panel are my 50 Amp EV charging circuit, my 30 Amp AC compressor, my 30 Amp electric dryer, and my 20 Amp dishwasher and garbage disposal plus some non essential receptacles.
I do have my FAU fan, all my lighting circuits (LEDs) most of my receptacles, a 30 Amp Heat Pump Water Heater and a 30 Amp EVSE recptacle on the critical loads panel. I am out of breaker spaces on my critical loads panel so that is another part that is a work in progress. I will have my electrician friend do a load analysis of I go to a larger panel. This latest heat wave has made me sensitive to the desire for some AC when the grid is down. I am glad I put the FAU fan in the loads panel because we use that to improve the air quality in the home. I might be able to get by with an efficient minisplit for the bedroom in the future. The point of all this is to build in flexibility which is important during these uncertain times.

Have you experienced a true power outage since you installed the Skybox and batteries? I'm wondering if you won't have to manually load shed breakers without a working grid at night to stay under the 5kw max of the Skybox.

With my recent decision to move away from the 15kW Sigineer inverter, I will need to be more selective on which circuits to put on the critical loads panel. Honestly speaking, in the decade I've been at this house, we've lost power for more than an hour only maybe 1 time. But with PG&E's Public Safety Power Shutoffs becoming a thing now, I want to be prepared, but not destroy my finances preparing for the unnecessary.

 

[GXMnow]

In the 17 years I have lived in this house, We have had only 3 power outages that we were not told about days in advance for "maintenance". Out of those, just one lasted more than a day. An underground cable feeding the transformer for the whole block got crushed because the conduit broke so they could not even pull in a new cable. They had to dig up 3 front yards to repair it and run a new cable. Of course, my yard was one of them. They left rocks on the surface and broke a sprinkler line, and fixed none of it. But since that cable has been replaced, we have not had an outage. But as these fires keep up and get closer, we have been warned of possible shut downs, and also rolling blackouts to handle heat emergencies. I figured the battery backup was due. And by also using it to do Time of Use shifting, it will reduce the cost some.

 

[Ampster]

I found the section where the application calculated my estimated generation and estimated usage. But I can not see any verbage stating "thou shall not generate more than this amount." See a snip of my NEM agreement attached.

View attachment 22488

I looked at mine and I could not find that wording either. Interestingly I thought mine was restricted to my inverter size of 3.8 but mine says 5.3 kW.

This is interesting and something for me to keep in mind if I ever get knocked off NEM1. Part of the motivation to go have the second solar array be DC coupled instead of expanding my current array, is to avoid touching my current NEM agreement. Any changes will automatically bump me into NEM2 and likely take me off of my E-6 TOU rate plan.

Yes there are advantages to NEM 1. I think the rates themselves are based on other factors not the NEM phase you are on. I have been on EV rates for eight years so I am in a special niche to get that Super Off Peak rate of around $0.15 per kWh. That E-6 rate is a tiered plan and I have steered away from tiered plans because of my previous high usage off peak.

Have you experienced a true power outage since you installed the Skybox and batteries? I'm wondering if you won't have to manually load shed breakers without a working grid at night to stay under the 5kw max of the Skybox.

With my recent decision to move away from the 15kW Sigineer inverter, I will need to be more selective on which circuits to put on the critical loads panel. Honestly speaking, in the decade I've been at this house, we've lost power for more than an hour only maybe 1 time. But with PG&E's Public Safety Power Shutoffs becoming a thing now, I want to be prepared, but not destroy my finances preparing for the unnecessary.

Yes I have had several but all of them were with my old Nissan Leaf pack which the limitation was in terms of kWhs. With my new pack I have gone to the self consumption mode on the Skybox that has me off the grid for my critical loads and only charging from solar. Essentially my critical loads panel has been running as if I was off grid since mid August and on the attached you can see the results of the first 11 days of September.

I think the most I ever drew was 4kW according to the attached. I drilled down and that was a brief morning peak when my wife was making coffee, running the toaster and the microwave and I didn't notice it until I looked at this chart. I think some of that may also be my heat pump water heater which I can program to come on later in the morning when solar will support more loads. As you can see on the 9th I had virtually no solar production because of the heavy smoke in the Sonoma Valley and the extra battery capacity carried me through. In eleven days I used almost 99 kWhs which is a daily average of about 9 kWh per day.

 

[apachexmd]

I've decided to go with a Skybox. It should be arriving this coming Monday. Also have (8) 370W bifacial panels coming too. I think I will get the panels and inverter installed and running before purchasing batteries. That should keep me busy for a little while; gotta buy/install the critical loads loadcenter, relocate a bunch of circuits, and relocate the existing grid-tie inverter feed. Then install the PV racking and panels. Should be fun!

Has anyone installed external CT's in with a Skybox? I'm having a hard time finding out what the CT specifications need to be.

 

[apachexmd]

Just to update this thread. I got the Skybox, and new PV panels installed and online. I had to rearrange a subpanel to become a critical loads panel, and rewire my existing PV breaker into the critical loads panel. But everything is up and running. They Skybox itself was a breeze to install (though a little heavy, get a helper!) and everything is laid out very nicely and integrated into a single unit. I am very pleased with how it came out.

I did find out that while the Skybox was originally advertised with a batteryless backup feature that allowed PV to power loads in a power outage, that feature has since been removed. I was hoping to have some backup power while I put together my batteries, but no luck there. I have some LiFePo4 cells coming on a slow boat from China, so once those are in, I'll be in a better spot backup-wise, and will start playing with the Time of use settings and see how Skybox behaves when trying to load shift.

And to answer the question in my last post, I ended up purchasing some generic 100A/100ma CT's from Amazon, because the Skybox has a "Custom" setting when enabling the CT option. I just set the Turns Ratio to 1000 (100A/1000=100ma). I installed the CT's at my main house panel right on the feeder wires from my utility meter. I guessed on the CT orientation, and of course they were reading power in the opposite direction the first time, so I just physically flipped them to get them reading correctly. They seem to be pretty accurate compared to the LCD display on my utility meter, within a 2-3% margin.

Since I started planning this project my expectations has been tempered a bit. I'm no longer expecting to charge my EV's on battery power, so the Skybox's 5000 watts should be plenty. With the installation of the CT's at the main breaker, I've been able to monitor my whole house's power usage in real time for the first time and it's very interesting to see the family's patterns. With COVID and work/school from home, this year is very atypical from years past, but who knows, this may be the new normal for a long time to come. I think once I get my batteries for backup and load shifting, I think I'll be in a good spot. Thanks for everyone's help and input!

 

[Ampster]

Thanks for the update. I will be curious how the Skybox behaves with the external CTs once you get your batteries. I may play with that concept in my head for a while. As i mentioned I am in self consumption mode after trying load shifting with time of use.

Longer term I have not found a way to have my Orion BMS communicate with the Skybox. That leaves me with the option of disconnecting the pack with a contactor.