Limited to 100 amp service from utility - options for more PV?

[jmzorko]

Hello, all ...

My home has 100 amp service from PG&E and I have a small 3kw PV array that came with the home that I would like to expand to 6-7kw. In a previous home, I just had the main panel upgraded and all was well, but with this home, the electrical service from the utility is underground. From what I've read, this could make a main panel upgrade far more expensive due to the digging involved.

Yet, 3kw is nowhere near enough to cover my needs. What options are there to expand the PV given the limitations of my 100 amp service? The inverter I'm planning to use is the Sol-Ark 5k, and I'm leaning toward the Fortress Power eFlex batteries. I also want the capability to run off-grid for extended periods if required (due to a bad experience in my last home that required us to be disconnected from PG&E for 3 months, where we lived off just solar and battery).

Regards,

John

 

[iamrich]

Not sure I understand your problem. Are you saying the panel is too small for your needs, or are you saying the panel is too small to accept a bigger PV array?

 

[time2roll]

I think you can upgrade to a 200 amp panel and still have a 100 amp main to increase the PV array.

The limit is due to the 100 amp panel driven by a 100 amp breaker cannot accept more power. Although if you add PV you can overdrive the panels by 20% (25%?) to feed 120 amps in total. Dang now if you have a 200 amp panel with a 100 amp utility feeder you could feed that panel with 100 amps from the PV array. This keeps you at the panel rating and potentially you could backed the utility at 100 amps. Actually you might be limited to 80 amps off the solar but still you should be able to go bigger.

 

[chrisski]

I don't see upgrading to PV being cheaper than having a ditch dug to connect to main power. This would be especially true if the additional power you want is the equivalent of a 200 amp hookup.

For panels installed on the roof for my area, I plan for $15k per 5 kw of grid tied system installed prior to rebates. It would take about 15 kw of panels for me to return as much power as I use. I have a 3500 sqft house and live in AZ. Getting batteries would add much more to the cost.

 

[jmzorko]

I think you can upgrade to a 200 amp panel and still have a 100 amp main to increase the PV array.

The limit is due to the 100 amp panel driven by a 100 amp breaker cannot accept more power. Although if you add PV you can overdrive the panels by 20% (25%?) to feed 120 amps in total. Dang now if you have a 200 amp panel with a 100 amp utility feeder you could feed that panel with 100 amps from the PV array. This keeps you at the panel rating and potentially you could backed the utility at 100 amps. Actually you might be limited to 80 amps off the solar but still you should be able to go bigger.

Are you suggesting that I can just upgrade the main panel on my house to 200 amp while retaining the 100 amp connection to PG&E, meaning there would be no digging? Is that an option? That would rock if so. I had a 7.5kw PV / single PowerWall system at my previous home which served us very well. I would like to have similar capacity at this home.

 

[jmzorko]

Not sure I understand your problem. Are you saying the panel is too small for your needs, or are you saying the panel is too small to accept a bigger PV array?

I think the latter. The last time I had a 3kw system, it was fine bc heating in that house was via natural gas and we worked at an office where I could charge my EV. Now we work almost exclusively from home (where I also charge, though not as often) and the heating in this house is handled by an electric heat pump, so 3kw isn't anywhere near enough. I'd very much like to go to 6-7kw, but the main panel doesn't have the capacity to do so.

 

[time2roll]

Are you suggesting that I can just upgrade the main panel on my house to 200 amp while retaining the 100 amp connection to PG&E, meaning there would be no digging? Is that an option? That would rock if so. I had a 7.5kw PV / single PowerWall system at my previous home which served us very well. I would like to have similar capacity at this home.

Verify with the city on what the permit requires. Your solar installer should also know.

 

[Hedges]

Are you suggesting that I can just upgrade the main panel on my house to 200 amp while retaining the 100 amp connection to PG&E, meaning there would be no digging? Is that an option? That would rock if so. I had a 7.5kw PV / single PowerWall system at my previous home which served us very well. I would like to have similar capacity at this home.

Should be, except you probably need a 100A main breaker, which may not be an option for the 200A panel. If not, you could put in a 100A fused disconnect and wire that to a 200A panel. 100A fuse (or breaker) means 80A maximum continuous current, 19.2kW

If you get a Square-D QO panel, it has 225A busbars. 120% rule means main breaker plus PV breaker can total 270A. Smallest main breaker is 150A, so put a 100A PV breaker at opposite end of the panel. Having a main breaker in this panel would be optional (since fed with fuses), but having a main means you can put an interlocked backfed "generator" input next to it. That's how I can power my main panel with output of inverter.

Plan your future battery backup while doing this.

With the fused disconnect, you could instead wire two breaker panels. One main panel for the house, other for PV (maybe input to a hybrid or battery inverter.) That can give you a UPS for critical loads. And the option to feed whole house from it (wired this way, grid backup to house.) With the right interlocked breaker setup you can bypass failed inverter and put loads back on grid.

A different option is line-side tap. It can be a ring adapter under the meter. I think the limit is 40A breaker, 32A continuous, 7680W

Your existing panel ... 100A breaker, but what is the panel rated? QO is 125A busbar, breaker can be 125A, 100A, 70A. If 125A busbar with 100A breaker, you can connect a 50A PV breaker for 40A continuous, 9600W

 

[jmzorko]

Should be, except you probably need a 100A main breaker, which may not be an option for the 200A panel. If not, you could put in a 100A fused disconnect and wire that to a 200A panel. 100A fuse (or breaker) means 80A maximum continuous current, 19.2kW

If you get a Square-D QO panel, it has 225A busbars. 120% rule means main breaker plus PV breaker can total 270A. Smallest main breaker is 150A, so put a 100A PV breaker at opposite end of the panel. Having a main breaker in this panel would be optional (since fed with fuses), but having a main means you can put an interlocked backfed "generator" input next to it. That's how I can power my main panel with output of inverter.

Plan your future battery backup while doing this.

With the fused disconnect, you could instead wire two breaker panels. One main panel for the house, other for PV (maybe input to a hybrid or battery inverter.) That can give you a UPS for critical loads. And the option to feed whole house from it (wired this way, grid backup to house.) With the right interlocked breaker setup you can bypass failed inverter and put loads back on grid.

A different option is line-side tap. It can be a ring adapter under the meter. I think the limit is 40A breaker, 32A continuous, 7680W

Your existing panel ... 100A breaker, but what is the panel rated? QO is 125A busbar, breaker can be 125A, 100A, 70A. If 125A busbar with 100A breaker, you can connect a 50A PV breaker for 40A continuous, 9600W

No one has yet been able to tell me exactly what the panel is rated as. PG&E only says "under 350 amps" when I ask them. The breaker in the main panel connecting me to grid power seems to be a 100 amp breaker, at least as far as I can tell. I've pinged a few electricians, so hopefully one can tell me this week what the panel is actually rated as. 7.6kw would be great, 9.6kw even better.

I'm planning on using the Sol-Ark inverter and will probably be ordering one this week, as well as the batteries.

I'm learning _so_ much from all of you! Many thanks!

 

[Hedges]

No one has yet been able to tell me exactly what the panel is rated as. PG&E only says "under 350 amps" when I ask them. The breaker in the main panel connecting me to grid power seems to be a 100 amp breaker, at least as far as I can tell. I've pinged a few electricians, so hopefully one can tell me this week what the panel is actually rated as. 7.6kw would be great, 9.6kw even better.

I'm planning on using the Sol-Ark inverter and will probably be ordering one this week, as well as the batteries.

I'm learning _so_ much from all of you! Many thanks!

Picture of the panel and its breakers would be a start.
If you're comfortable removing cover to expose interior, a picture there could show label with ratings.
If you turn off the main breaker first, the only live parts should be the screw terminals where wires connect to main breaker.

With Sol-Ark or another hybrid, best setup might be a line-side tap feeding it, and it feeds critical loads. During a power failure you could manually flip interlocked breakers to backfeed your panel, power anything you want.

Possibly, Sol-Ark will support using current transformers to measure power delivered to grid, allowing you to over-panel and produce more power so long as you consume it. Although, line-side tape may put a limit on the breaker size allowed.

Before buying I suggest you plan out the entire installation, including inverter, panels, rapid-shutdown if required, batteries, etc. and check on permit requirements.

 

[iamrich]

No one has yet been able to tell me exactly what the panel is rated as. PG&E only says "under 350 amps" when I ask them. The breaker in the main panel connecting me to grid power seems to be a 100 amp breaker

The size of the input wire from the grid should be a good tell.

 

[jmzorko]

The size of the input wire from the grid should be a good tell.

View attachment 58433

I took this photo when the installer asked me to open the panel to determine the rating. He said he thought it was most likely 100 amps given the size of the wires into the breaker. I didn't measure them exactly, though.

 

[Hedges]

That appears to be a service entrance with 100A breaker, separate from your breaker panel for loads. That's the best situation.
(I don't know what the extra 20A is for)

You can flip off the 100A breaker, no need to have PG&E shut anything off when changing your breaker panel. Then install a 200A (or 225A) panel and put PV breaker on it.

You can alternately split the connection from this breaker using Polaris connectors or split-bolts, and run wires to two breaker panels.
If one is PV and can backfeed current (in addition to 100A coming from utility), the sum of those current would go through wires to other breaker panel. In that case, wires and panel busbars need to be large enough to handle the current, or put a "main" breaker in panel to limit current.

These moderate thickness aluminum wires appear to be what feeds your breaker panel. The two busbars exiting left appear to go to utility meter and the grid. The question for PG&E would be what's the largest breaker you're allowed to connect (what gauge wires they used.) You appear to have 100A + 20A = 120A connected.

 

[iamrich]

I took this photo when the installer asked me to open the panel to determine the rating. He said he thought it was most likely 100 amps given the size of the wires into the breaker. I didn't measure them exactly, though.

I agree with Hedges, you should be able to convert your panel to anything you want by just flipping those two breakers. Always test for power before doing anything of course, but flipping those two breakers should kill all the power to your house.

If you install a big enough inverter/solar array/battery pack, it wont matter what your grid input is rated for. Most houses could run off a single 20a circuit if they have a big enough solar setup. The grid can help charge your batteries all day 24/7 at low current and your batteries/solar take do most of the grunt work. This assumes you are not going to back feed the grid though. This is the setup I plan on running when I build my house. I am going to have a big ass array, inverter(s), and battery storage and just sip off the grid if needed.

 

[jmzorko]

That appears to be a service entrance with 100A breaker, separate from your breaker panel for loads. That's the best situation.
(I don't know what the extra 20A is for)

You can flip off the 100A breaker, no need to have PG&E shut anything off when changing your breaker panel. Then install a 200A (or 225A) panel and put PV breaker on it.

You can alternately split the connection from this breaker using Polaris connectors or split-bolts, and run wires to two breaker panels.
If one is PV and can backfeed current (in addition to 100A coming from utility), the sum of those current would go through wires to other breaker panel. In that case, wires and panel busbars need to be large enough to handle the current, or put a "main" breaker in panel to limit current.

These moderate thickness aluminum wires appear to be what feeds your breaker panel. The two busbars exiting left appear to go to utility meter and the grid. The question for PG&E would be what's the largest breaker you're allowed to connect (what gauge wires they used.) You appear to have 100A + 20A = 120A connected.

The extra breaker is for the PV ... which makes me wonder: If the cumulative sum of the breakers is indicative of the service rating from PG&E, does that indicate that my service is greater than 100 amps? I'm hopeful that I can hire an electrician tomorrow to tell me definitively what my service is rated at.

 

[iamrich]

The extra breaker is for the PV ... which makes me wonder: If the cumulative sum of the breakers is indicative of the service rating from PG&E, does that indicate that my service is greater than 100 amps? I'm hopeful that I can hire an electrician tomorrow to tell me definitively what my service is rated at.

We really need to see the other side of the breaker (the wires coming in from the top) to tell for sure, but based off the output wires, you have 100a service.

Edit: Hmmmm, I am actually confused now, because I don't see any wires coming into the top. I need to look at the picture a bit more I think

 

[jmzorko]

I agree with Hedges, you should be able to convert your panel to anything you want by just flipping those two breakers. Always test for power before doing anything of course, but flipping those two breakers should kill all the power to your house.

If you install a big enough inverter/solar array/battery pack, it wont matter what your grid input is rated for. Most houses could run off a single 20a circuit if they have a big enough solar setup. The grid can help charge your batteries all day 24/7 at low current and your batteries/solar take do most of the grunt work. This assumes you are not going to back feed the grid though. This is the setup I plan on running when I build my house. I am going to have a big ass array, inverter(s), and battery storage and just sip off the grid if needed.

Indeed, this is what i'm hoping for, with the addition of being able to be off-grid for extended periods if required.

 

[time2roll]

The extra breaker is for the PV ... which makes me wonder: If the cumulative sum of the breakers is indicative of the service rating from PG&E, does that indicate that my service is greater than 100 amps? I'm hopeful that I can hire an electrician tomorrow to tell me definitively what my service is rated at.

Assuming a permit and inspection was performed on a professional install this would seem to be correct. Although not a confirmation as some of these go in without a full compliance understanding and 3kW is just 12.5 amps.

 

[jmzorko]

So, the Sol-Ark (5K) arrived, as well as 21 kwh of batteries. The electrician is arriving tomorrow to replace the Delta inverter with the Sol-Ark (and reroute things so it's in the garage vs outside). This is my plan - thoughts?

1. replace current Delta inverter with Sol-Ark (tomorrow)
2. create sub panel and move critical loads to it (whenever the electrician can schedule it)
3. connect batteries to Sol-Ark (I think I can do this part)

... at this point I'll be off-grid capable for short periods (a few days perhaps if the batteries are completely charged) but my current 3kw array is nowhere near large enough to recharge them fully. So ...

4. find a way to add 3-4 more kwh of solar to my current system, given the limitations of my current 100 amp service from PG&E.

It's that last part that I'm still unsure of. I don't want to run afoul of any permits, I just want to have enough PV to completely cover my electricity usage.

 

[Hedges]

There's adding more panels, and there is wiring for more amps.

Depending on efficiency of your panels, newer models may put out 50% more power in the same space, so replacing them on the same mounts could be an option.

If you have another mounting location with different orientation, two arrays can be put into two separate MPPT of an inverter. Two identical voltage arrays (strings) can be paralleled on a single MPPT, even if different orientation. Multiple orientations gives lower peak current, more hours production.

A 100 A panel may per spec be allowed 20A PV breaker, which should be used at 80% or 16A max.
There should be a few ways to tie in a larger breaker. Maybe just a larger PV breaker adjacent to that 100A breaker in the meter box.