New system 2x sol ark 15k's 400 amp service - 5 subpanels

[uxooaw]

So I have a building with 4 small 2/1 units. It is in SDGE territory in CA and has a huge flat sunny roof (all single story).

Currently the building has 5 meters and 30 amps each unit. We are looking to upgrade the service.

The plan is, replace existing 5 meters (4 units + house) with a single meter 400A main service. Feed this through 2 sol-ark's in parallel and out to 4x 100a sub panels one in each unit. I am thinking these would be Leviton smart panels with whole home energy monitor with ct's to track usage.

Plus a small emergency load panel for the house meter (lighting, security cameras ect).

The part I'm having trouble figuring out exactly is the path, we would have the 400A meter base with 2x 200A breakers feeding into the 2 15k's, then should those two 15k's feed a single 400A panel with breakers for the 100A subpanels?

We would install ~15KW solar and start with 30kWh of batteries - but would have plenty of room to add more solar/batteries later to support potentially more EV charging in the future.

The way I see it we could increase the rent ~$100 a month and simply include electric in rent. We would have a clause about reasonable usage and EV charging would be tracked via CT and billed at a flat rate per kwh. This would also let us attract new tenants easier, allow us to reduce the number of meter account charges billed by SDGE from 5 to 1, and would also be eligible for a tax credit.

Planning to install hybrid mini splits for each unit as well, so those likely wouldn't eat into things too bad even if ran often.

Thoughts?

 

[zanydroid]

This is getting into legal territory where you want to do a lot of due diligence before proceeding.

Well there is that proposal to nerf VNEM that people were talking about a lot today on the forum. VNEM at present I believe allows you to credit the NEM credits from shared facilities to the tenant bills. I don’t know if they also want to nerf the Solar Billing Plan equivalent of VNEM.

Also you need to look into what the PUC has to say about effectively selling electricity in a way that bypasses VNEM

There may also be a building code minimum for the feeder to each living unit. I thought it’s 100A for current code, will wait for the electricians to get in on this. I vaguely remember something about individual metering too.

(Ah your plan has the correct size per unit).

 

[uxooaw]

This is getting into legal territory where you want to do a lot of due diligence before proceeding.

Well there is that proposal to nerf VNEM that people were talking about a lot today on the forum. VNEM at present I believe allows you to credit the NEM credits from shared facilities to the tenant bills. I don’t know if they also want to nerf the Solar Billing Plan equivalent of VNEM.

Also you need to look into what the PUC has to say about effectively selling electricity in a way that bypasses VNEM

There may also be a building code minimum for the feeder to each living unit. I thought it’s 100A for current code, will wait for the electricians to get in on this. I vaguely remember something about individual metering too.

(Ah your plan has the correct size per unit).

I've been researching a bit. The VNEM would work, however there's a few big negatives to it, IMO. Negative #1 is that all the solar power would flow out one meter and back in the individual tenant meters (Which all have to be in the landlord's name for VNEM), thus accruing non-bypassable charges. Negative #2 is that because of this setup installing batteries is not possible unless individually installed for each unit. Negative #3 is that the division of power must be setup up-front as percentages and can only be changed once a year, so there's potential to waste credits if tenant usage changes or someone with an EV moves in/out. Negative #4 is that SDGE is contemplating increasing per meter fees. Positive is if I pulled the trigger right now could skate by under NEM 2.0.

This service upgrade is going to likely last the building for 50+ more years, and locking into 5x meter fees at whatever SDGE decides to make them in the future sounds like a poor choice.

On the downside, going with a single meter would put it under NEM 3 which would mean low credits for sold power requiring power to be stored and used. Although with the way prices of LFP batteries and solar panels are going it would seem this is the better bet.

I already have a similar setup in a commercial building for quite some time where the solar on the roof basically leaves me with a $1k /year true up bill, but the tenant pays me $400 a month for their power. It's worked great for 5+ years and with electric rates so high in SDGE area, it makes a ton of sense, IMO.

The downside I see is that if we ended up with alot of EV charging usage during evening this could deplete the battery quickly. But EV charger would have its own CT and be billed to the tenants who have EV's at ~30c/kwh. So if this happened we could just add more battery storage and/or solar to solve it and the ROI would be fairly decent.

Anyone else do or contemplate doing anything similar?

 

[pvgirl]

Make sure you understand landlord tenet law around utilities and submetering. You may need to install a revenue grade meter for each tenet even if it's not used for billing. 100amp is the minimal size for a residential service, but you will want to a load calculation to determine if that will be sufficient.

 

[uxooaw]

Make sure you understand landlord tenet law around utilities and submetering. You may need to install a revenue grade meter for each tenet even if it's not used for billing. 100amp is the minimal size for a residential service, but you will want to a load calculation to determine if that will be sufficient.

The units are quite small, ~650 square feet. We did a load calc and came up with 70A being more than enough, but doing the 100A so each unit can allow each a 30A 240v EV charger.

Revenue grade meters aren't that expensive and we're going to need to install them on the water lines anyway to meter out the individual water usage.

Anyone have recommendations on the best brand of metering?

 

[zanydroid]

The units are quite small, ~650 square feet. We did a load calc and came up with 70A being more than enough, but doing the 100A so each unit can allow each a 30A 240v EV charger.

100A is just a flat minimum rule

The VNEM would work, however there's a few big negatives to it, IMO.

#1 and 2 are kind of clearly better than NEM3, no?
2 may get worse with sharper TOU fees, which are already terrible with SDGE. Since I’m in PG&E I haven’t really gamed out scenarios for SoCal power prices

Note also this means I have a bias for caring a lot about winter energy credits. For you the EV charging may need it, for us in cold climate we need it for both EV and heating

Also you may not be thinking exploitatively enough about NEM2. Under VNEM are you allowed to program batteries to force export only during peak? This will defeat the TOU problem. Then you don’t need individual unit batteries, you are just using the grid and VNEM accounting to simulate it. It also pushes summer credits into a bank for winter, which is straight up impossible with NEM3

3 is tough too but I imagine it’s still better than NEM3

I have advocated for SFRs to getting in on NEM2, with the cheapest possible gridtie equipment, and then rip and replace or AC retrofit once UL9540 ESS have Sane prices. Don’t get a hybrid now. That was optimal under NEM2 to ESS transition rules . Not sure if they apply to VNEM.

There’s nothing that says you can’t switch if finances switch later, perhaps it’s possible to set up the wiring to be easy to convert. For instance using convertible separate subpanels behind a meter main that serves strictly as a shutoff

 

[uxooaw]

I appreciate this.

 

[zanydroid]

If the plan is AC coupled retrofit then maybe don't go with the cheapest possible gridtie equipment because it needs to live a long time in that situation.

Probably game it out with an assumption that UL9540 DC coupled ESS inverter (that you are allowed to use with server rack form factor or wall battery form factor, at EG4 prices) will be $2000 in 2 years vs $5500 right now.