I made a big mistake and didn’t realize it soon enough

[BackCountry]

I have never limited export. Don't now how.
However, how would SMA know what the net export is? Seems like SMA would just measure gross solar output at the inverter, not net export at the meter??

Also, I second splitting arrays across orientations - if cost effective. Especially E-W if relatively steep pitch. However, if shallow pitch, won't make much diff.
Of course depends on specifics of array and roof.

Unfortunately that won’t work, it’s a ground mount, already built, and they don’t consider orientation with the CEC-AC sizing

 

[BackCountry]

Had that happen to me with PG&E before, maybe 8 or 9 years ago. The numbers are a little hazy but it was something like we had a 1,200A service SWBD and did not find out until the interconnection application phase that PG&E had only given them a 300kVA pad mounted service transformer. This was a municipal design bid build project so the interconnection phase did not happen until the contractor started the build process. The PV system I was working with was something like 350kW AC. Upsizing the transformer to what was normally the next size up at 500kVA was not possible because PG&E said they were discontinuing that size so they could only provide a 750kVA and since that was way over the load they would charge a fee every month for the oversized transformer. We were using SolarEdge inverters but PG&E would not accept the export limiting system that was built in, we had to either install an expensive non-export relay or have the factory limit the output of the inverters. We went with the factory limit option. Good luck.

That one makes sense to me considering the size, we have always pre-applied for greater than 30kw to flush out any details. This is 23kw, I’d have never imagined this being possible, and I know why…

10kva overhead transformer = 13kw max
15kva overhead transformer = 19.5kw max
25kva overhead transformer = 32.5kw max

This of course applies if it’s only one customer fed from the transformer, which in this case is correct.

So the gray area only applies if you’ve got a small transformer, and your sizing is greater than 13kw or smaller than 30kw, or 19.5 depending on the transformer. It’s a narrow range.

The option for power control systems is new, I know nothing about it beyond using it for storage systems — I’ve never tried it for oversized PV systems, but I’m hoping it works! It does make sense, small transformer but high usage means offset usage and export less than max.

 

[winnie]

I have never limited export. Don't now how.
However, how would SMA know what the net export is? Seems like SMA would just measure gross solar output at the inverter, not net export at the meter??

SMA has a video out about this. It requires an energy meter (CTs and such) to actually measure what is being exported. Apparently (with the appropriate hardware) you can limit export to a certain value, force zero export, or even force a certain minimum import of power.

The cost of lots of really expensive infrastructure gets hidden from the customer. 21K for an upgrade to a customer who might use very little total energy is not entirely unreasonable. But if self consumption pretty well matches PV production, meaning there is naturally minimal export, then this upgrade is never actually going to be used, and will instead be there 'just in case' there is lots of PV export. Export limiting seems a great tool for this, and as a member of the peanut gallery I hope the POCO accepts it.

-Jon

 

[electrofelon]

$21,000??
Thats ridiculous. Those XFs cost us about $1500 each for a 25kVa.
Takes two guys 30 minutes to change out.

Yeah I was going to say that's absurd. I believe in my area we get a $300 charge if a transformer needs to be upgraded up to 25 KVA (yeah I know that is cheap, but it's what the tariff says). Maybe the op can appeal that amount?

 

[GoldDigger]

ComEd here does something similar. It is based on their estimate of the total cost of the installation over its lifetime converted to current dollars. It is a reasonable way to charge for such things IMO. Why should other ratepayers now and in the future pay for equipment that is dedicated to you?

Maybe my financial math is lacking something, but how can the cost of a $1500 transformer "over its lifetime" calculate to $21,000?
Or do you mean they are caclulating the cost of the total energy lost in powering an oversized transformer? At an energy cost growing 5% per year?

 

[BackCountry]

Yeah I was going to say that's absurd. I believe in my area we get a $300 charge if a transformer needs to be upgraded up to 25 KVA (yeah I know that is cheap, but it's what the tariff says). Maybe the op can appeal that amount?

It’s absolutely nuts. They do say the cost is plus or minus 50%; however, even $10,000 is insane. See attached.

 

[BackCountry]

SMA has a video out about this. It requires an energy meter (CTs and such) to actually measure what is being exported. Apparently (with the appropriate hardware) you can limit export to a certain value, force zero export, or even force a certain minimum import of power.

The cost of lots of really expensive infrastructure gets hidden from the customer. 21K for an upgrade to a customer who might use very little total energy is not entirely unreasonable. But if self consumption pretty well matches PV production, meaning there is naturally minimal export, then this upgrade is never actually going to be used, and will instead be there 'just in case' there is lots of PV export. Export limiting seems a great tool for this, and as a member of the peanut gallery I hope the POCO accepts it.

-Jon

I watched that video also. It seems pretty simple, I’ve installed plenty of CT’s on customer owned meters. If they’ll accept that, then I think that’s our solution.

 

[petersonra]

Maybe my financial math is lacking something, but how can the cost of a $1500 transformer "over its lifetime" calculate to $21,000?
Or do you mean they are caclulating the cost of the total energy lost in powering an oversized transformer? At an energy cost growing 5% per year?

It is not just the transformer, but the pole, and the wiring and everything else associated with it that has to be maintained over the next 50 years or whatever.

 

[wwhitney]

It is not just the transformer, but the pole, and the wiring and everything else associated with it that has to be maintained over the next 50 years or whatever.

Right, but in the case of a transformer upgrade, what is the delta in those maintenance costs? Seems low or zero. So just looking at the immediate equipment and labor costs to effect the change would be fair.

Cheers, Wayne

 

[ggunn]

It is not just the transformer, but the pole, and the wiring and everything else associated with it that has to be maintained over the next 50 years or whatever.

But it's not like they have to install a pole that wasn't there before, is it?

 

[BackCountry]

But it's not like they have to install a pole that wasn't there before, is it?

Correct, it’s an existing pole and there’s nothing else to change, simply swap out the existing transformer

 

[jaggedben]

It looks to me like the 'initial' estimate is pretty boilerplate and probably higher than the final costs will be, but I assume you'd have to risk the $1500 or so deposit to find out.

 

[electrofelon]

Seems borderline criminal to me. I wonder what the PUC would think or what the tariff actually says about these costs.....

 

[LarryFine]

Upgrading the service may trigger a larger transformer without the cost being passed on.

 

[tortuga]

For what its worth around here they don't stock or install 10kva anymore so pretty soon that will get swapped out with a 15 or 25 on a maintenance upgrade.
Is this project in a rural area that has wild fire risk?
A transformer or HV line upgrade in a rural area can trigger a wild fire risk assessment witch can result in removing the pole and converting to underground and padmount.

PG&E moves power underground in plan to bury 10,000 miles

Pacific Gas & Electric Co. is working on an ambitious project to bury thousands of miles of power lines in an effort to prevent wildfires sparked by its equipment and to avoid shutting down power during hot and windy weather

abcnews.go.com

 

[BackCountry]

For what its worth around here they don't stock or install 10kva anymore so pretty soon that will get swapped out with a 15 or 25 on a maintenance upgrade.
Is this project in a rural area that has wild fire risk?
A transformer or HV line upgrade in a rural area can trigger a wild fire risk assessment witch can result in removing the pole and converting to underground and padmount.

PG&E moves power underground in plan to bury 10,000 miles

Pacific Gas & Electric Co. is working on an ambitious project to bury thousands of miles of power lines in an effort to prevent wildfires sparked by its equipment and to avoid shutting down power during hot and windy weather

abcnews.go.com

It is rural but I don’t think they’re going to underground this any time soon.

 

[BackCountry]

It looks to me like the 'initial' estimate is pretty boilerplate and probably higher than the final costs will be, but I assume you'd have to risk the $1500 or so deposit to find out.

Yes. I have another one in progress right now that’s a 25kva to a 50kva, I was hoping it would be completed before this so we could see the real cost!

We had another job where they set a clearance pole, upgraded a transformer, and put in about 200’ of service wire to our customer owned pole, and that one was $21k. A lot more work though.

 

[electrofelon]

If there is one thing I have learned after 20 years in the electrical trade is utility construction costs are all over the place. Had one service upgrade a few years ago that required a new 3 phase pole bank and drop and the POCO paid for all of it. Then another new 480 200 A OH service that was $16k. You just never know.

 

[Hv&Lv]

If there is one thing I have learned after 20 years in the electrical trade is utility construction costs are all over the place. Had one service upgrade a few years ago that required a new 3 phase pole bank and drop and the POCO paid for all of it. Then another new 480 200 A OH service that was $16k. You just never know.

A lot of that also depends on whether it’s a muni, co-op, or for profit POCO.

 

[ggunn]

A lot of that also depends on whether it’s a muni, co-op, or for profit POCO.

Not that it helps in this case, but if you find the issue before the system is built you will have the customer on your side, hence more leverage with the utility.