Advice for installing storage system

[Ampster]

I couldn't find any details on how to calculate the SGIP rebate or the maximum amount allowed in my case. Does anyone know? What I do know is that I was told I could get a $26,400 rebate on a $27,900 2 Powerwall 2 system.

I live in Sonoma and briefly thought I could get some of those rebates. I did some investigation and found I was just outside of the critical area even though I had public power shutoffs. What I also discovered was the big incentives had income limitations and that would have reduced my compensation or eliminated my participation. The foregoing may not apply to you, but I am offering it as advice to guide you through your investigation of the details. My best advice when evaluating investments like this, is to check and recheck your assumptions. That is especially true in a situation where you may commit to something an installer tells you about a very large rebate.

Speaking of PowerWalls, Tesla has the best prices but they have reached their quota on SGIP rebates. As a result, third party installers have jumped into the market but marked up the prices to the point that the difference between their price and Tesla's is the rebate. Also do not confuse the Federal Tax incentive with the SGIP rebate. They are entirely different and you still get the Federal Tax credit with a Tesla system. I once had a deposit on a PowerWall with a third party but cancelled that to install a hybrid system. I can go into details if you are interested.

I don't mind manual load management. That is what I do now. I have a generator input on my house subpanel (with interlock) and choose what loads to run when. This allows me to run loads that wouldn't be able to run if I only had a critical loads subpanel. My main concern would be if the system automatically switched to backup and it couldn't handle the existing load. If everything shutdown without damage I'd be OK with that.

That may save you some money. Your system is complicated and you are almost at the point that it might be worth the cost to get a basic electrical system design. Some of that cost may qualify for Federal Tax credit depending how it is structured. This is not tax advice but another assumption to check with your tax professional.

Depending on how the rebate is structured, "oversizing" the storage system may be the cheapest alternative.

All I can say is that one aspect of the rebate is based on kWhs of storage. That was one consideration when I cancelled the PowerWall. This is where distinguishing between kW of power capacity and kWhs of storage (energy) capacity is important. The short answer was that I did not need the power of two PowerWalls but I wanted the ability to last through a long power outage with lots of kWhs of battery capacity. I figured I could self install a hybrid system with the Power of one PowerWall and the battery capacity of two PowerWalls for a lot less than the inflated cost of two third party installed PowerWalls.

NOTE: I subsequently found a SGIP website and the two largest rebates were $0.85 to $1.00 per Watt so that is in the ballpark of what you were told for twomPowerWalls, each of which has 13.5 kWhs of useable capacity. Both those programs had "Eguity" in the description which I assume may be the programs for disadvantaged communities or incomes below a threshold. That is an assumption that needs to be checked and verified.

[Ampster]

My string inverter is over 7 years old and is not CA Rule 21 compliant (as far as I know). It looks like I should consider replacing the old inverter also.
But it does currently play nice with my new Enphase system.

Replacing an inverter is a piece of cake compared to mounting panels and racking on a roof. Replacing a string inverter with a hybrid inverter is a little more complicated because the hybrid inverter also has a transfer switch and the hybrid inverter needs to be matched with a critical loads panel that should not exceed the kW capacity of the hybrid inverter. Some of them have generator inputs and you may be able to use some of the infrastructure of your existing Generator transfer switch. Depending on how the panels on the roof are configured you may be able to use them as is. My hybrid inverter can handle a wide range of string voltage.
I am not sure what you mean when you say your old inverter plays nice with your Enphase system? That is not rocket science when the grid is up. The challenge is when the grid is down and you want to leverage existing grid tie solar with AC coupling. The advantage of some hybrid inverters is they can DC couple to an existing string and AC couple to a system like your Enphase micros.

[RKCRLR]

The only reason your old inverter would need to be replaced is that it would not be capable of AC coupling with a hybrid inverter effectively. In other words depending on your loads it would toggle between on or off. The Enphase IQ7s can modulate power. They AC couple with most hybridvinverters which are compatible with CA Rule 21. BTW most string inverters last 7 years so if your older inverter is that old it may be worth replacing it with a hybrid inverter..

My string inverter is over 7 years old and is not CA Rule 21 compliant (as far as I know). It looks like I should consider replacing the old inverter also.
But it does currently play nice with my new Enphase system.

[RKCRLR]

Does the SGIP program recognize Lead Acid systems? I think there is some requirement for manufacturers warranty period to qualify for that incentive. LG Chem, BYD, Enphase Ensemble are a few in addition to Tesla Powerwall.

I couldn't find any details on how to calculate the SGIP rebate or the maximum amount allowed in my case. Does anyone know? What I do know is that I was told I could get a $26,400 rebate on a $27,900 2 Powerwall 2 system.

I don't mind manual load management. That is what I do now. I have a generator input on my house subpanel (with interlock) and choose what loads to run when. This allows me to run loads that I wouldn't be able to run if I only had a critical loads subpanel. My main concern would be if the system automatically switched to backup and it couldn't handle the existing load. If everything shutdown without damage I'd be OK with that.

Depending on how the rebate is structured, "oversizing" the storage system may be the cheapest alternative.

[Ampster]

Does the SGIP program recognize Lead Acid systems? I think there is some requirement for manufacturers warranty period to qualify for that incentive. LG Chem, BYD, Enphase Ensemble and SimpliPhi are a few in addition to Tesla Powerwall. I don't know the details of how SGIP certifies capacity but one constraint may be finding an installer who is familiar with Lead Acid systems and willing to to the paperwork for the rebate. Most of the installers I talked with were electricians that had rebranded themselves to capture the business of installing systems and processing the SGIP paperwork. They had no experience with Lead Acid. At this point in the evolution, Lead Acid has become a niche relegated mostly to off grid installations.

[Mike90250]

Your high power, optional loads (spa, oven, electric heaters) need to be on a separate panel that will not be energized by your battery backup. No smart breaker and computer will be fast enough to cut the heavy loads before the inverter shuts down.

What is the vaporware transfer switch capacity ? 60A 150A 250A ?? (until they ship yours, they are vaporware. Learned that long ago)

Your well pump is a critical load, and you should have some water storage (3k - 9k gallons) too.

Batteries- only reason to use Li batteries (powerwall) is if your power co will allow load shifting/selling and you can save bunches of $$ (to pay for the $$ Li battery)

Otherwise, go for a smallish lead acid battery that is on float most of the time, and when the power cuts off, the system switches over and after 2 minutes, the generator starts up.
Or size the battery for overnight power so you don't have to listen/worry about the generator when sleeping.

Lots of choices to think through. Propane or diesel for the generator ?

[RKCRLR]

Running another conduit at this point would be ugly. I'd have to go through landscaping, lawn, concrete patio or have a long circuitous route.
One thing I forgot to mention is I have Ethernet (and a spare Cat-5 cable) between my house and the outbuilding. And the outbuilding has wifi.
I saw some smart breakers online but I have no idea how they work.

[Ampster]

I would make an assessment of your critical loads and get a second opinion about whether a critical loads panel can be installed. I have seen a number of installs where sub panels were cascaded off other sub panels. If you are planning on powering your entire house you will need at least two Powerwalls anyway. That is over 20 kWhrs of storage and 14kW of peak power. I would compare that extra expense with the cost of 250 feet of conduit if that is the only way to separate the loads. The existing conduit may be capable of carrying two smaller sets of wires. I don't know how the rebate covers infrastructure upgrades but I recall it is based on kWhrs of capacity. The Federal tax credit is calculated on the total cost so there may be som support there.

Outback and others have generator support and can use batteries that can scale up. Enphase Ensemble is a great system that starts small but I am not sure it scales up cost effectively.

The only reason your old inverter would need to be replaced is that it would not be capable of AC coupling with a hybrid inverter effectively. In other words depending on your loads it would toggle between on or off. The Enphase IQ7s can modulate power. They AC couple with most hybridvinverters which are compatible with CA Rule 21. BTW most string inverters last 7 years so if your older inverter is that old it may be worth replacing it with a hybrid inverter..

[RKCRLR]

I'm in California and it appears I qualify for a substantial rebate for installing a storage system since I'm in a high wildfire risk area with safety shutdowns and am on a well. I'm working with my solar installer for a bid (as well as another competitor) but my system is complicated so I thought I'd get some advice for my options. I want to have battery back-up with the ability to keep the solar going when the grid goes down. A bonus would be the ability to recharge the batteries using a generator when the grid goes down during the winter.

I have 2 separate solar systems installed on an outbuilding. One is an older 4KW string system. The other is a recently installed (last year) 6KW Enphase/Panasonic system with IQ7 microinverters.

My 400 amp combination service entrance panel/load center is mounted on the outbuilding. It has 2 branches. One branch goes through a 200 amp breaker (no load center) to feed my subpanel at my residence (about 250' away). The other branch goes through a 150 amp breaker to feed the integrated load center for the outbuilding. My solar systems are tied into this load center.

My solar installer is leaning towards an Enphase Ensemble system. An advantage of this system is the new transfer switch coming out has the ability to accept generator output. A problem with this is I would need to replace my string inverter with Enphase microinverters (as far as I can tell) for the 20 200W panels on my old system.
I'm also getting a bid for a Powerwall 2 system.

As far as I can tell, the storage system will need to be installed at the outbuilding and tap into the branch feeding my residence down there.

One concern I have is what happens when the grid goes down and the system automatically switches over to backup while the demand (A/C, spa, oven, well, etc. is running) exceeds the system capability? I'm assuming it does some kind of shutdown. Do I risk damage to my system or appliances in my house?

How would I know when the system is switched over? I'd like to shut down unnecessary items to conserve storage.

Normally you'd put in a separate subpanel for critical items but it isn't practical because of the distance between the outbuilding and my residence.

Are there other systems that would have an advantage in my situation?

Thanks