San Diego Coastal

[albert436]

It's usually the difference between on peak and off peak rates for a day, summed over some period of , say, 30 or 365 days that are used to determine the cost effectiveness of a battery system.

Also, the optimal and most cost-effective way to reduce an energy bill is through conservation.
Fact of life: The 100% savings on unused energy are impossible to beat.
Time shifting of loads without batteries is probably the next most cost effective.

Yeah I probably need new 10-12 windows in the front although those don't come free either.

Time shifting of loads, not sure what you mean by that. You mean not using electricity during peak hours, doing things at different times of the day?

[albert436]

I have a couple of issues at this moment that I am sorting out.

I sent this email to SDGE after talking to two people on the phone and being re-directed. Dang it I forgot to ask about adding a battery, although it seems like there is pretty good agreement that it will not kick you off your NEM status. Heck I think I will just write another email.

Dear Sir/Madam,

I have been told by SDGE (telephone contact) that it will be OK for me to have aggregate metering for the three meters on my 2 on 1 property here in Ocean Beach, as all three meters are in my name. I am living in one unit and using the other solely for visiting family and friends. The third meter is for a laundry area where I will also be replacing a previously existing gas-heated hot tub with an all electric one.

My question is this: I don't have much space on my SW facing roof for panels, and one solar company has suggested I could put additional panels on the roof of the other unit, which is a completely separate structure. Another solar company has said that is not allowable, something to do with fire codes was my understanding.

Can you clarify this for me?

I also would like clarification on roof setbacks for firefighter personnel access. Could you also advise me on this?

Thank you,

[Ampster]

I think those are building code issues and if you haven't got an answer yet I suspect they will direct you to your local building department. Typically the IOUs are only concerned with what goes on at their meter and not beyond. What I mean is they are only concerned with the power going through the meter, not how the panels are attached to the roof or wired to the inverter.

The question I have is with regard to NEM Aggregation? I have a NEMA agreement which is about 12 years old and I have heard, but not investigated that there are some changes in NEMA and NEMV and wondered if you had any insight?

[albert436]

I think those are building code issues and if you haven't got an answer yet I suspect they will direct you to your local building department. Typically the IOUs are only concerned with what goes on at their meter and not beyond. What I mean is they are only concerned with the power going through the meter, not how the panels are attached to the roof or wired to the inverter.

The question I have is with regard to NEM Aggregation? I have a NEMA agreement which is about 12 years old and I have heard, but not investigated that there are some changes in NEMA and NEMV and wondered if you had any insight?

I got a really quick reply to my email directing me to the section of their website that discusses aggregate metering, but which did not mention about the panels on two separate roofs. So I have sent them back an email asking if they noticed that question. I suspect you are right about SDGE having nothing to do with building codes, though they did not even suggest I contact that agency so go figure. Maybe I will try to figure out who to call.I think you mentioned an different power company than mine, which is SDGE.

I don't even know what NEMA and NEMV are. I can just say that I called SDGE, waited on hold for a while, talked to someone who then transferred me to another department, who said I needed to email my question in to the people who handle that.

What I'm trying to say is that they were pretty responsive and it took a little while but wasn't too bad in terms of waiting on hold. So hopefully your power company will be as responsive as SDGE.

[Ampster]

.........

I don't even know what NEMA and NEMV are. I can just say that I called SDGE, waited on hold for a while, talked to someone who then transferred me to another department, who said I needed to email my question in to the people who handle that.
.......

NEMA is NEM Aggregation. It sounds like your case where you have contiguous buildings with separate meters and you want to apply the credits from one meter to the other meters.
NEMV is NEM Virtual Net Metering. It is where the credits from generation after suppling loads from the main panel can be applied to other meters in the building. It is typically done in multifamily housing where the tenants get some benefit to to solar owned by the landlord.

My NEMA is with SCE and I am doing the research on that issue because that NEM agreement may only have eight years left and I may want to upgrade it to NEM 2.0 to get another 20 years. I understand that the 20 years is not guarantied but I am looking into that risk versus the guess that I have eight years or less.

[albert436]

NEMA is NEM Aggregation. It sounds like your case where you have contiguous buildings with separate meters and you want to apply the credits from one meter to the other meters.
NEMV is NEM Virtual Net Metering. It is where the credits from generation after suppling loads from the main panel can be applied to other meters in the building. It is typically done in multifamily housing where the tenants get some benefit to to solar owned by the landlord.

My NEMA is with SCE and I am doing the research on that issue because that NEM agreement may only have eight years left and I may want to upgrade it to NEM 2.0 to get another 20 years. I understand that the 20 years is not guarantied but I am looking into that risk versus the guess that I have eight years or less.

Thanks for explaining all that. I think I am going for the NEMA. They said I can do it if all the meters are in my name, which they are. I'm thinking of keeping the extra unit for friends and family to visit. I had an unpleasant tenant and getting her to move out was not easy.

I like your idea of extending your NEMA for an additional net 12 years, seems like a winner.

[albert436]

Another question. Is it OK to put panels from the same system on two separate units ?

I'm getting incrementally closer to an answer on this. I think what I understand is that the wires from the 2nd structure need to be routed back to the primary meter for the other panels. Ie. it can't just come down to the subpanel on that structure. I think because I am trying to do aggregate or virtual metering, I can't have the panels coming to that subpanel. Anyway, the meter for that structure is back by the alley with the other two meters. Yes this is a bit over my head and I'm just feeling my way forward.

But those wires will have to be put underground. I have over the top mid air wires now for electric but I think my place was grandfathered in, being many decades old. The trenching for putting them underground could be a formidable (and expensive) task. There are supposed to be some alternatives for places where solid rock is encountered. I had found a page that gives the appropriate SDGE department phone number to inquire about that but seem to have lost it. I'm back home and am going to comb through all my open tabs. I don't know if I could get a dispensation for roots or lack of room for a trench or whatever. Probably not but I prefer to leave no stone unturned in my quest for energy self-sufficiency!

Or maybe I am doing this and should just be happy with 14-16 x 400W panels on the one roof . . .

[Ampster]

I'm getting incrementally closer to an answer on this. I think what I understand is that the wires from the 2nd structure need to be routed back to the primary meter for the other panels. Ie. it can't just come down to the subpanel on that structure. I think because I am trying to do aggregate or virtual metering, I can't have the panels coming to that subpanel.

I do not fully understand your layout but there are lots of options. It may be useful to separate building code issues from SDGE issues. Cost may dictate which option is optimal. Depending on the size of the subpanel, an inverter could be connected to that subpanel but that is just a building code issue and has nothing to do with SDGE.

But those wires will have to be put underground. I have over the top mid air wires now for electric but I think my place was grandfathered in, being many decades old. The trenching for putting them underground could be a formidable (and expensive) task. There are supposed to be some alternatives for places where solid rock is encountered. I had found a page that gives the appropriate SDGE department phone number to inquire about that but seem to have lost it. I'm back home and am going to comb through all my open tabs. I don't know if I could get a dispensation for roots or lack of room for a trench or whatever. Probably not but I prefer to leave no stone unturned in my quest for energy self-sufficiency..........

The whole purpose of NEM Aggregation is to allow an owner of several contiguous parcels to have solar systems that can be aggregated to several meters. That is a SDGE issue and it seems one option for you if the cost of trenching it too much. In this case you would have two systems, one on each building. Micro inverters may be economical if installing less that ten panels and a structure.

[J.P.M.]

Or maybe I am doing this and should just be happy with 14-16 x 400W panels on the one roof . . .

I'd suggest one possible goal is being happy with what you want.

But to do that, you need to begin with 2 pieces of information:

1.) Which loads or portions of loads you want to offset.

2.) Estimates of how big each of those loads are.

[albert436]

Anyway, here is what I finally decided.
First company gave me a proposal of ~21K for 6.4kW, another gave me a quote of around 17K.
Then I started asking can I put a few more panels on the roof of the other house and have them all on the same system. The lower offer guy said no way, there would need to be trenching and underground placement etc etc which would make it quite expensive. The other guy checked with their engineer/design guys and said they could do it, adding 4 panels to make it an 8kW system and that no underground etc. would be needed. It would be ~27K which would include all electrical work.
Another very highly rated company came out and give me a proposal for the same thing but it was more, 30K and change. The funny thing is, the proposal mentioned "Hawaiian Tie-in". Which I had to google of course. I think that is why no underground trenching would be necessary and I'm guessing that is what company with the 27K proposal is using, although the sales guy was kind of coy about it when I asked him.
Please google it, there is a discussion on an electricians' forum, and quite a difference of opinion about exactly what it means, what it is, and why it conforms to code. Quite interesting but over my head. I'd be interested if anyone could boil it down to a lay person's level.
So yeah I am going with the 8kW system for ~27K.
Thanks to everyone for your input!