Off-Grid Home Backup - California

[mjsfbay]

Greetings all.

I wanted to see if someone out there would be able to give me some input regarding the subject line.

Background:
I have an existing, underpowered system with utility interconnect agreement. The system was installed it approx. 2018.
- SolarEdge SE5000H
- 3.71 kWp array
- Average usage = 175 kWh/month
- True up this year will be $500+

I’m looking for a solution that fits below criteria.

Qualifiers:

1. Does not require utility interconnect agreement
2. Does not require permits (Northern California)
3. Does not require a critical load panel build out (preferably).
4. Does not require a transfer switch (preferably).

Purpose:

1. Backup power
2. Reduce electric bills
3. Future proof for EV charging

Questions:

1. How would you configure such a project?
2. Would 6000xp with 14.3 kWh storage be sufficient?
3. How would you go about a 50ft run from home through concrete slab (finished backyard) for solar array?

My thought was to build out a separate off-grid system. The trouble I’m having is understanding how to accomplish the goals stated above without needing to modify my utility interconnect and/or pull permits.

I think I have a basic understanding of how a general system should work. I become confused when figuring out the best and easiest installation to connect the inverter to existing equipment for backup and on demand use - without risking code violations.

How would you go about accomplishing this?

 

[SolarFlares]

Greetings all.

I wanted to see if someone out there would be able to give me some input regarding the subject line.

Background:
I have an existing, underpowered system with utility interconnect agreement. The system was installed it approx. 2018.
- SolarEdge SE5000H
- 3.71 kWp array
- Average usage = 175 kWh/month
- True up this year will be $500+

I’m looking for a solution that fits below criteria.

Qualifiers:

1. Does not require utility interconnect agreement
2. Does not require permits (Northern California)
3. Does not require a critical load panel build out (preferably).
4. Does not require a transfer switch (preferably).

Purpose:

1. Backup power
2. Reduce electric bills
3. Future proof for EV charging

Questions:

1. How would you configure such a project?
2. Would 6000xp with 14.3 kWh storage be sufficient?
3. How would you go about a 50ft run from home through concrete slab (finished backyard) for solar array?

How would you go about accomplishing this?

Are you keeping your connection to the grid in any capacity? Or going completely off grid?

 

[mjsfbay]

Keeping grid connection.

I just realized I left out an important detail and should go into more detail on this.

I’ll add this detail to original post.

Thanks for the great question @ SolarFlares!

 

[SolarFlares]

You are currently under NEM 2.0. I don't know if you notify them that you are modifying your system if you will be moved to NEM 3.0?

Someone else can chime in who went through this process but you could probably change out your system and if you had enough batteries and limited your export to your current export amount, they would probably not know anything has changed.

If it were me, I would start planning to go completely off grid. CA does not want residential solar. NEM 3.0 makes that very clear. You live in an area that is highly regulated but you don't like all the regulations. You either need to go completely off grid or move to an area where you are not under CA's rules.

 

[BentleyJ]

I have an existing, underpowered system with utility interconnect agreement. The system was installed it approx. 2018.
- SolarEdge SE5000H
- 3.71 kWp array
- Average usage = 175 kWh/month
- True up this year will be $500

Qualifiers:

1. Does not require utility interconnect agreement

You already have one, so any new solar capacity has to be strictly Self Consumption with batteries, no new export. This means you will need a UL1741SB compliant inverter capable of AC Coupling.

1. Does not require permits (Northern California)

Anything electrical of this scope would require a permit in CA. Although not everyone complies.

1. Does not require a critical load panel build out (preferably).

Then you must back up the entire main panel which requires the connection from the meter to be removed before the main breaker then fed to the new hybrid, grid interactive inverter (which is large enough to handle the whole house amperage) Then the output of the new inverter feeds the main breaker in the house panel. This may require an electrician who may or may not wish to do the job without a permit.

1. Does not require a transfer switch (preferably).

The inverter will have a built in transfer switch (really its more of a utility disconnect). Its a good idea to install a maintenance bypass system so utility power can be sent directly to the main panel if the inverter fails or needs service.

Purpose:

1. Backup power
2. Reduce electric bills
3. Future proof for EV charging

All Good

Questions:

1. How would you configure such a project?

See above

1. Would 6000xp with 14.3 kWh storage be sufficient?

NO, for 2 reasons. Its an off-grid product, no UL1741SB or AC coupling capability and It doesn't have the capacity to run the whole house both because the AC pass thru relay is rather small (50A I believe?) and the inverter capacity is questionable for whole house.

1. How would you go about a 50ft run from home through concrete slab (finished backyard) for solar array?

?? Directional trenching. If you can find someone to do a small job. Its usually done on a utility or industrial scale.

My thought was to build out a separate off-grid system. The trouble I’m having is understanding how to accomplish the goals stated above without needing to modify my utility interconnect and/or pull permits.

A totally separate system is exactly the opposite of not wanting a critical loads panel. Either way some of the breakers in the main panel would have to moved to the new panel, whether its part of your main system or totally separate.

 

[mjsfbay]

Thanks for your reply @BentlyJ.

You confirmed all my fears regarding building out such a system.

Is it absolutely necessary that there be a permanent coupling? I’d like for the off grid system to be able to operate independently on demand.

This brings me to another hard issue you answered- the critical loads panel. I came to the realization this morning that there’s no way around it - but there’s something to be gained here. Here’s a strategy I think may work:

1) Install subpanel close to main panel and transfer all circuits except for the main landing and existing solar circuit.

2) use this panel to connect an inverter (6000xp vs. EG4 12k vs. EG4 18k), off-grid array and battery bank.

3) I’ve seen a couple YouTube videos where a tap is placed on the subpanel feed, and directed to off grid inverter to charge the battery bank as needed - in this situation it seems like an interconnect bracket would be needed to prevent back feeding.

What are your thoughts on this build?

It seems like this should work, but I recall there being a necessity for some devices to be connected directly to the main panel. Do you recall such an issue?

Thanks for putting a name to the concrete issue I asked about. Google calls it Directional Boring. I’m not sure that’ll be possible for my case, but I’ll look into it!

 

[mjsfbay]

You are currently under NEM 2.0. I don't know if you notify them that you are modifying your system if you will be moved to NEM 3.0?

Someone else can chime in who went through this process but you could probably change out your system and if you had enough batteries and limited your export to your current export amount, they would probably not know anything has changed.

If it were me, I would start planning to go completely off grid. CA does not want residential solar. NEM 3.0 makes that very clear. You live in an area that is highly regulated but you don't like all the regulations. You either need to go completely off grid or move to an area where you are not under CA's rules.

My understanding is, to stay under NEM 2.0, I can modify/add to the system up to the current inverter (perhaps even swap it out), but I cannot change the size of my array.

Off grid sounds great in theory, but I’m not sure how I’d configure an off grid system and still maintain power export from the existing array - without raising a bunch of flags…

Maybe if I used the grid to charge batteries periodically it would prevent there being 90+% export?

 

[SolarFlares]

My understanding is, to stay under NEM 2.0, I can modify/add to the system up to the current inverter (perhaps even swap it out), but I cannot change the size of my array.

Off grid sounds great in theory, but I’m not sure how I’d configure an off grid system and still maintain power export from the existing array - without raising a bunch of flags…

Maybe if I used the grid to charge batteries periodically it would prevent there being 90+% export?

When I say off grid, I mean disconnect from the grid permanently. Do an analysis of your power usage and solar generation by month and see how close you are to being fully off grid.

https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP
https://solarpanelsvenue.com/solar-battery-calculator/

I think your idea of making a new panel and having 2 separate systems is complicated and prone to issues. What if you are away for a weekend and someone is at your house and needs assistance? Keep it simple and similar to accepted designs and it will be cheaper in the long run.

 

[mjsfbay]

When I say off grid, I mean disconnect from the grid permanently. Do an analysis of your power usage and solar generation by month and see how close you are to being fully off grid.

https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP
https://solarpanelsvenue.com/solar-battery-calculator/

I think your idea of making a new panel and having 2 separate systems is complicated and prone to issues. What if you are away for a weekend and someone is at your house and needs assistance? Keep it simple and similar to accepted designs and it will be cheaper in the long run.

Great points! I don’t disagree.

Issue is I have this grid tied system that I’m still paying off. I want there to be some benefit to it.

Even if I don’t run my loads through it, under NEM 2.0, I’m still getting credit for exported energy.

So, I’m just trying figure out the best way to keep that going while using an off grid system as my main power.

Forgot to add, I have very limited space for panels…. That’s why I’m looking into solar pergolas or some other structure that’ll allow me to mount panels across a concrete slab while giving me some room to use my backyard for other things.

 

[DIYrich]

Do you have an Integrated Meter/Main Panel, or separate? If Integrated, creating an off-grid type system will require a lot of work.

Otherwise:
Grid <> Existing Solar -> Inverter -> Main Panel
or
Grid ->
Inverter -< Existing Solar
Inverter -> Main Panel

Inverter: Eg4 18kpv or Sol-ark 15k with Batteries.

 

[mjsfbay]

Do you have an Integrated Meter/Main Panel, or separate? If Integrated, creating an off-grid type system will require a lot of work.

Otherwise:
Grid <> Existing Solar -> Inverter -> Main Panel
or
Grid ->
Inverter -< Existing Solar
Inverter -> Main Panel

Inverter: Eg4 18kpv or Sol-ark 15k with Batteries.

The meter and main panel are integrated.

 

[BentleyJ]

Is it absolutely necessary that there be a permanent coupling? I’d like for the off grid system to be able to operate independently on demand.
1) Install subpanel close to main panel and transfer all circuits except for the main landing and existing solar circuit.

AND a double pole breaker to feed the AC Input of the hybrid inverter. Having a permanent connection between the main panel and inverter only gives you the OPTION of using utility power for pass-through or battery charging. You are not forced to use it.

2) use this panel to connect an inverter (6000xp vs. EG4 12k vs. EG4 18k), off-grid array and battery bank.

6000XP is an off grid inverter while the 12K and 18K are grid interactive and would allow AC Coupling. They would have to be set up with CT's and grid export would have to be limited to what the existing system has historically sent back to the utility

3) I’ve seen a couple YouTube videos where a tap is placed on the subpanel feed, and directed to off grid inverter to charge the battery bank as needed - in this situation it seems like an interconnect bracket would be needed to prevent back feeding.

Based on the question, I believe you are missing some pieces of the system layout. With a main panel and a subpanel, you don't need any "taps" just a breaker in one of the panels to feed the inverter input.
Backfeeding is prevented in various ways depending on the type inverter you are using.

EDIT: BTW, batteries can be charged with a plug in stand alone charger from any outlet.

 

[SolarFlares]

Great points! I don’t disagree.

Issue is I have this grid tied system that I’m still paying off. I want there to be some benefit to it.

Even if I don’t run my loads through it, under NEM 2.0, I’m still getting credit for exported energy.

So, I’m just trying figure out the best way to keep that going while using an off grid system as my main power.

Forgot to add, I have very limited space for panels…. That’s why I’m looking into solar pergolas or some other structure that’ll allow me to mount panels across a concrete slab while giving me some room to use my backyard for other things.

I get that but at some point you have to decide and then build something for the long term. If you keep cobbling things together you're not going to end up where you want.

 

[Hedges]

What would happen if you added a few kW of similar size PV panels, together with SolarEdge optimizers?
And didn't tell anyone?

You've also got the option of StorEdge, which takes an (expensive) HV battery.

You could alternatively install a hybrid that supports AC coupling.
Wire SolarEdge downstream of it. Or upstream of it, then AC coupling not used.
It may be able to let SolarEdge export to grid, and use its DC coupled PV + battery to minimize imports.
It's battery would perform peak shaving and carry you though the night, leaving SolarEdge production to earn net-meter credits to use during winter.

 

[mjsfbay]

AND a double pole breaker to feed the AC Input of the hybrid inverter. Having a permanent connection between the main panel and inverter only gives you the OPTION of using utility power for pass-through or battery charging. You are not forced to use it.

I was thinking the inverter would be powered by the battery bank?

But… I think this actually is an alternative solution to my #3!

6000XP is an off grid inverter while the 12K and 18K are grid interactive and would allow AC Coupling. They would have to be set up with CT's and grid export would have to be limited to what the existing system has historically sent back to the utility

CT = external energy meter, right?

I want to avoid this at all costs!

Based on the question, I believe you are missing some pieces of the system layout. With a main panel and a subpanel, you don't need any "taps" just a breaker in one of the panels to feed the inverter input.
Backfeeding is prevented in various ways depending on the type inverter you are using.

EDIT: BTW, batteries can be charged with a plug in stand alone charger from any outlet.

Great to know I can charge batteries in such a way. This would simplify things as it would avoid a direct connection to a panel.

This is one of the videos I’m referring to regarding the taps: (@18:15 mark)

Easy DIY Home Backup Solar Power System & Battery - 6000xp Install and Test

 

[mjsfbay]

I get that but at some point you have to decide and then build something for the long term. If you keep cobbling things together you're not going to end up where you want.

Can’t disagree with you on this.

 

[mjsfbay]

What would happen if you added a few kW of similar size PV panels, together with SolarEdge optimizers?
And didn't tell anyone?

You've also got the option of StorEdge, which takes an (expensive) HV battery.

You could alternatively install a hybrid that supports AC coupling.
Wire SolarEdge downstream of it. Or upstream of it, then AC coupling not used.
It may be able to let SolarEdge export to grid, and use its DC coupled PV + battery to minimize imports.
It's battery would perform peak shaving and carry you though the night, leaving SolarEdge production to earn net-meter credits to use during winter.

Edited for clarity:

Coupling configurations… This where I become confused and lost in the reeds. I can’t visualize how I’d do this.

A disadvantage I see is that these solutions would void my installer’s warranty… (whatever that’s worth).

 

[Hedges]

CT = external energy meter, right?

I want to avoid this at all costs!

Current transformer, which may connect to internal energy meter of some inverters.

They generally already have CT on their internal grid connection. Can have external to go at utility connection so they can zero or limit exports while backfeeding to supply house loads.

I'm playing with Sunny Boy Storage, an AC coupled battery system that shaves peaks & valleys attempting to do zero export for a system with separate AC coupled GT PV.

You might want a hybrid/AIO to supply house loads while avoiding export in excess of what your NEM agreement allows.

 

[DIYrich]

This brings me to another hard issue you answered- the critical loads panel. I came to the realization this morning that there’s no way around it - but there’s something to be gained here. Here’s a strategy I think may work:

1) Install subpanel close to main panel and transfer all circuits except for the main landing and existing solar circuit.

2) use this panel to connect an inverter (6000xp vs. EG4 12k vs. EG4 18k), off-grid array and battery bank.

Since you have an integrated Meter/Main panel, this is the way to go. The Sub-Panel becomes your new Main Panel.

I would use an EG4 18k or a Sol-Ark 15k. The EG4 12k is limited to 80 Amp passthrough. If you have a 100 amp panel, that would be ok.

Put the Solar Edge into the Gen port of the 12k/18k/15k. That will make the PV available when grid is down.

You could use the 6000xp per your original plan if you don't care about loosing Solar Edge when grid is down.

3) I’ve seen a couple YouTube videos where a tap is placed on the subpanel feed, and directed to off grid inverter to charge the battery bank as needed - in this situation it seems like an interconnect bracket would be needed to prevent back feeding.

Since you have NEM2, exporting to the grid is not a problem. You can set it to never exceed the 3.7kW that you currently have.

 

[billvon]

Greetings all.

I wanted to see if someone out there would be able to give me some input regarding the subject line.

Background:
I have an existing, underpowered system with utility interconnect agreement. The system was installed it approx. 2018.
- SolarEdge SE5000H
- 3.71 kWp array
- Average usage = 175 kWh/month
- True up this year will be $500+

I’m looking for a solution that fits below criteria.

Qualifiers:

1. Does not require utility interconnect agreement
2. Does not require permits (Northern California)
3. Does not require a critical load panel build out (preferably).
4. Does not require a transfer switch (preferably).

Purpose:

1. Backup power
2. Reduce electric bills
3. Future proof for EV charging

Questions:

1. How would you configure such a project?
2. Would 6000xp with 14.3 kWh storage be sufficient?
3. How would you go about a 50ft run from home through concrete slab (finished backyard) for solar array?

My thought was to build out a separate off-grid system. The trouble I’m having is understanding how to accomplish the goals stated above without needing to modify my utility interconnect and/or pull permits.

I think I have a basic understanding of how a general system should work. I become confused when figuring out the best and easiest installation to connect the inverter to existing equipment for backup and on demand use - without risking code violations.

How would you go about accomplishing this?

Comments:

1) If you already have a NEM 2.0 agreement - do not give that up!

2) The only ways around the critical loads panel are fairly ugly; mechanical interlocks that do not allow automatic switchover, for example. If there's really some structural reason why you can't do it then that may work. If there are no such reasons, they are worth the money.

3) The "clean" way to do this is to install a critical loads panel fed by a new AIO inverter/battery set to zero export. In your case you'd want to move all but the really high loads to the critical panel so you can take advantage of removing their loads. And it's utility transparent so they won't see the new generation (and you can keep NEM 2.0/)

4) A less clean way to do it is to install a new AIO on the same panel and then use its CT sensors to limit export to a number less than what your max export is now. It's not strictly following your net metering agreement because now you can export more energy, but you can massage the export to make it not much different (i.e. only enabling export during daylight hours.) But now you are violating the letter of the agreement, if not the intent.

 

[mjsfbay]

Current transformer, which may connect to internal energy meter of some inverters.

They generally already have CT on their internal grid connection. Can have external to go at utility connection so they can zero or limit exports while backfeeding to supply house loads.

I'm playing with Sunny Boy Storage, an AC coupled battery system that shaves peaks & valleys attempting to do zero export for a system with separate AC coupled GT PV.

You might want a hybrid/AIO to supply house loads while avoiding export in excess of what your NEM agreement allows.

Edit:

AIO = All-In-One. Disregard previous statement that the technology was over my head.

Thanks for sharing your thoughts on this issue.

 

[mjsfbay]

Comments:

1) If you already have a NEM 2.0 agreement - do not give that up!

2) The only ways around the critical loads panel are fairly ugly; mechanical interlocks that do not allow automatic switchover, for example. If there's really some structural reason why you can't do it then that may work. If there are no such reasons, they are worth the money.

3) The "clean" way to do this is to install a critical loads panel fed by a new AIO inverter/battery set to zero export. In your case you'd want to move all but the really high loads to the critical panel so you can take advantage of removing their loads. And it's utility transparent so they won't see the new generation (and you can keep NEM 2.0/)

4) A less clean way to do it is to install a new AIO on the same panel and then use its CT sensors to limit export to a number less than what your max export is now. It's not strictly following your net metering agreement because now you can export more energy, but you can massage the export to make it not much different (i.e. only enabling export during daylight hours.) But now you are violating the letter of the agreement, if not the intent.

Option 3 seems like the way to go. If zero export is enabled that would mean I wouldn’t be in danger of backfeeding during an outage, right? Or do the EG4s have a smart setting preventing this even with limited export setting enabled?

 

[billvon]

If zero export is enabled that would mean I wouldn’t be in danger of backfeeding during an outage, right? Or do the EG4s have a smart setting preventing this even with limited export setting enabled?

There are two questions you are asking here.

1) If I set to zero export does that mean I export zero power? - Yes, close to that. AIO's have a response time, so you won't get exactly to zero, but it will be close. If you did not have a NEM agreement that might cause a problem, but since you do, the few watt-hours you might accidentally export are a non-issue; they will be lost in the noise.

2) If the power goes out will a UL1741 rated hybrid inverter feed back to the grid? No, it will never do that - whether zero export is enabled or not. They are designed to drop the grid if it goes out of limits (i.e. during a blackout) so that utility workers are not endangered.

 

[mjsfbay]

Since you have an integrated Meter/Main panel, this is the way to go. The Sub-Panel becomes your new Main Panel.

Just for my clarification: moving all circuits to another panel would be a subpanel - but I’d be using it as a main panel, right? Are there any limitations to using a panel downstream from the main panel?

I would use an EG4 18k or a Sol-Ark 15k. The EG4 12k is limited to 80 Amp passthrough. If you have a 100 amp panel, that would be ok.

Understood.

Put the Solar Edge into the Gen port of the 12k/18k/15k. That will make the PV available when grid is down.

Will it attempt to export energy to the grid in this scenario? Or would it just be utilized for real-time power and/or export to battery storage?

Also, let’s say the input cables from SolarEdge are not long enough to reach the Gen port of new inverter - how would you go about extending them to reach?

You could use the 6000xp per your original plan if you don't care about loosing Solar Edge when grid is down.

This option is enticing…the 6000xp is a lot cheaper and we’ve had very few outages here. Even in this case, the battery storage should kick in.

Since you have NEM2, exporting to the grid is not a problem. You can set it to never exceed the 3.7kW that you currently have.

They wouldn’t be interested in the sharp increase of exported engergy?

 

[mjsfbay]

There are two questions you are asking here.

1) If I set to zero export does that mean I export zero power? - Yes, close to that. AIO's have a response time, so you won't get exactly to zero, but it will be close. If you did not have a NEM agreement that might cause a problem, but since you do, the few watt-hours you might accidentally export are a non-issue; they will be lost in the noise.

2) If the power goes out will a UL1741 rated hybrid inverter feed back to the grid? No, it will never do that - whether zero export is enabled or not. They are designed to drop the grid if it goes out of limits (i.e. during a blackout) so that utility workers are not endangered.

Beautiful! Thanks for your succinct answer.

Edit: Follow-up question

With your recommended configuration- it seems the critical load panel would essentially be reliant on off-grid power. How would you configure the panel to be backed up by grid if batteries are depleted and the sun isn’t out?