It sure looks like you are being treated as a commercial account versus a residential. Many states passed simplified interconnect procedures for renewable generation but usually limited it to 10 KW max. Anything over and your connection was treated as a regular interconnect. What you need to do is get a copy of the interconnect rules and see what they say. If they violated the rules its time to contact the PUC that regulates that utility.

How about putting in a 7.7kW inverter and orient at least 1/3 of the PV panels to a different direction so the inverter is not overloaded by this size of array? Won't have to buck the backfeed rule this way either. This situation is what we are going to be dealing with more and more as we see higher solar penetration rates, so let's not make enemies with the power companies.
Also, locate your inverter close to the service panel, as you don't want any more voltage drop than necessary with this many neighbors exporting power and lifting the grid voltage...

That transformer will need an upgrade if they are telling the truth, the question is who
must pay for it. An 8KW inverter capability is the alternative. Here in the country my
neighbor and I in the 70s started out with all electric homes so we each have our own
transformer. I wonder if that is why I could be permitted 15KW solar, no problem?

If you have frequent clouds in your area, you might be able to justify a lot more panels
tied to a single smaller inverter. Here a group faces the rising sun, another the setting
sun, running hard for 8 hours. Under the dispersed light of clouds they manage to
generate a lot more energy than a single set facing south. Bruce Roe

My annual usage is 11kW, so I am not over-generating in terms of my own usage. I know this is considered high for residential, but still, not over 100% on my particular site. I would be sad but willing to drop it to 10kW, and simply leave some panels out (they are ordered but aren't on the roof yet). I'm all microinverters here, so I can do whatever mod I want in my design. But no way am I going to 8.7k... I'm really trying to get my annual bill near zero to justify my cost.

They already weaseled out of net-metering in my state, this calendar year is the LAST year to get in the program. For the past 10 years they would pay a 1:1 ratio (100% rate), but this year is reduced to 90% (so even if I produce 11kW, I will still owe them a little), next year... poof, gone.

Anyway... I too want to keep things positive, but I am NOT going to just bend over on this. I will propose this: If I must pay for the transformer, I will own it. I will charge a 90% fee for all power flowing through it at the established rate until my investment is paid back 2x, at which point I will relinquish my ownership back to them. And I want this in contract.

Anything less is unethical. It is completely absurd for me to pay for a utility component that the entire community is using (I am not the only benefactor). Nobody in America sits down and disects their electric bill based on how much wire was in use, which transformers were in use, which trucks were operating that month, what insulators cost, cost of substations along the route, etc, etc. No. We simply, collectively, pay a monthly fee that COVERS ALL the costs to provide that UTILITY - a public utility.

Like I said, I pay for the equip on my side, THEY need to pay for the equip on their side. Anything less is completely unreasonable. Their demand is currently wildly unreasonable and inappropriate.

And with a fair amount less total annual output per installed STC kW than one array facing south, meaning less cost effectiveness.

I appreciate your's and the OP's situation, but it may be one where, for reasons beyond the OP's control, and fair or not, the reality is that PV generated electricity just might not be cost effective compared to plain old, non sexy, grid tied electricity.

Haven't heard any mention of annual loads from the OP. A 100% electric usage offset is not a mandate. More than a few applications and POCO billing practices can often make < 100% usage offset more cost effective per $$ invested than 100%. FWIW, an array that provides an ~ 85 % +/- a few % usage offset for me is the sweet spot that would maximize my ROI if I was doing it today. Every application is unique, but the way things are today and have been for as long as I've been looking at the #'s, in the cost effectiveness arena, there's little to be gained by poor design or oversizing.

dapug, just curious what state are you in? And how much $ are they asking to upgrade the transformer? I have not heard anyone having this problem before.

Unfortunately that is the case in many states. I serve on an interconnect working group where we recently studied interconnection standards in multiple states in order to make recommendations to our public utility authority..

A few examples
New York max infrastructure upgrade cost under 25kW AC system $350
Conn, Mass upgrade cost 100% on customer who triggers need, Utility pays for transformer, customer pays for labor and materials to install, including ne polei if necessary typical cost $1200-$5000
California probably best policy in nation utility (ratepayers) pays for all upgrades up to I believe 2MW AC

Andy

Sorry, I had some numbers slightly wrong.

My annual usage is 19,900kwhr /yr. This would require roughly a 12kW system for "100%", not including any clouds, efficiency losses, etc. Which means my 11kW setup is going to actually be about 91% capacity on paper.

At their requested 8.77kW max, I would sit at 73% generation, on paper. A loss of some "savings" monthly (adds up over the years), and at a loss of probably $3500+ of gear (panels, microinverters, racking) that will sit out, collect dust. Not thrilled.

I'm in Utah. PacificCorp (aka Rocky Mountain Power). They are supposed to tell me the cost of the transformer tomorrow - dunno yet (but regardless of the "that's the way it is" crowd, anything over $0 is literally unethical for reasons already explained).

In their eyes, you are yet another RE customer who wants them to pay to upgrade their system today so that tomorrow you can stop purchasing 91% of your power from them. You also expect their grid to always be ready to provide 100% of your energy needs if the clouds appear or when night falls. Believe it or not, utilities don't like RE customers playing in their sandbox. Hope they work things out with less of an impact for you.

It's not just you. My town has so many solar farms that they are not allowing any more to be built. The current transmission lines can not handle any more. Everyone wants to do what they want and stick the bill to someone else. Nothing new here.

People don't appreciate the value of the electric grid. The grid is a fundamental reason why we have prosperity like no time in history. Don't like the grid? Just go try and be off-grid. Lots of people do, but they live a simpler (possibly better) life. The cost of upgrading an on-grid system to an off-grid system of comparable capability is monumental. Your little 8kW inverter would need to be 25 times bigger (plus attendant batteries and everything else) to match the power the grid provides the typical home.

The best solution is for everyone to cooperate with the utilities and everybody share power. Yes, the utilities are bloated monopolies and could operate better, but the times they are a changin - I think we are going to see utilities reduced to just a monopoly over the transmission network and generation (and pollution) become competitive. Unless we see a miracle occur in battery technology, or the NRC gets off their duff and promotes molten salt reactors, we all can expect a future of more expensive energy production.

IMO 19,900kwhr /yr seems like a lot of residential use. Is there no possibility for conservation which would decrease the needed size of the system?

Not exactly. They ended net-metering here, no longer obligated to pay me for what I generate, and I wont be able to generate anywhere near 91% of my total costs anymore. They should be happy that I'm not off-grid and I'm still subscribing to and paying them for their service for night and all else. This is how this entire thing is SUPPOSED to be.

Not exactly. If the transformer is insufficient, then its on them to upgrade it. I'm not interested in doing something only for ME and then have someone else stuck with the bill. In fact, I have no problem paying for my PART of the upgrades, but I have a HUGE problem being the exclusive party paying the FULL brunt of a component used by the ENTIRE community, profiting the power company, and neither they nor the community have to chip in. That is not ok. Not one bit ok. I am 100% against "free handouts" and simultaneously 100% against being unfairly charged.

Tell me about it. My AC is the main draw. Extreme heat here, and my house construction sucks - I'd like to punch the builder in the face for not building it efficiently. My AC is brand new, perfectly tuned, sized correctly, and runs 16 hours a day NON-STOP during the summer, and even then only drops the temp to barely tolerable. That is not supposed to happen. They aren't designed to run that long. I also have an abnormal amount of electronics draw, running my own servers for video surveillance, etc. I can find a few places to trim the fat, but I will never get it down to anywhere near 8kW.

Your AC heat load might consist of house leakage, and the electrical equipment heating
it inside. Check what happens when the equipment is turned off.

Cleaning up house leakage will help. If the equipment is dominating the problem, how
about putting it into a very well ventilated but NOT air conditioned room? As for the AC,
I put one in in 2014 with a SEER of 14.5, it was a disappointment. In 2018 I put in 3 of
these for zone heat/cool, with a SEER of 33. The electrical consumption was greatly
reduced, and there are a few other high tech advantages.

If you are stuck with roof mount micro inverters, not much can be done with the array.
Bruce Roe

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