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A California Bay Area homeowner exploring rooftop solar received a costly warning before signing a contract: PG&E might replace a neighborhood transformer for free but still charge thousands for related engineering work.
The customer said the shared transformer was already at 96% capacity across 21 households and was told extra costs could range from $1,000 to $5,000.
In a Reddit post, the homeowner said the utility told them it would pay for a transformer replacement if it decided one was needed. At the same time, the utility said the customer could still be charged for engineering drawings and other installation-related work, and the poster wanted to know whether a new solar system would set off those expenses.
A commenter from the same region who had already gone through interconnection said, “The only way you will find out exactly what will happen is for your installer to fill in an Interconnect Application,” adding that the utility would then determine whether engineering work was needed.
That commenter said the utility presented two options: keep exports below the system’s nameplate capacity or pursue full export, which would mean a transformer upgrade and a new service line to the house.
They said the utility paid for the transformer, while they paid for a new power line costing “just under $2,000.” The commenter also said the process could take up to six months and that their service remained at 200 amps, with no main-panel change, before and after the upgrade.
Going solar is one of the best ways to save money on home energy, and interested homeowners can try EnergySage to get free solar installation estimates and compare quotes.
The thread highlighted how hard it can be for homeowners to get a clear answer on possible upgrade costs before the utility completes a formal review.
The poster was trying to avoid agreeing to an installation without first knowing whether they could end up paying for work on a transformer shared by multiple homes.
Several commenters said the issue isn’t just whether solar cuts a home’s use of grid power. One commenter said the bigger limit can be backfeed, writing that the key concern is “peak EXPORT,” which is “probably around 12-1. They upgrade the transformer if it can’t handle total export.”
Another commenter said a solar project can trigger utility-side upgrades because of “peak kVA, uneven loading, phase imbalance, voltage rise/AVR regulation and other protections.”
One more said the utility didn’t charge them and described the process as a “crapshoot.”
Commenters said the process begins when the installer submits the interconnection application and the utility starts its engineering review.
Based on the discussion, that review is when homeowners find out whether they need a full upgrade, can accept a lower export limit instead, and whether the utility will pass any costs on to them.
With EnergySage’s help, the average person can save up to $10,000 on solar purchases and installations. Homeowners can also use EnergySage’s solar map to see the average cost of a home solar panel system by state, along with details on solar panel incentives for each state. Together, these resources can help homeowners get the best price for rooftop solar panels and access available incentives.
Adding battery storage to a solar setup is one of the best ways to protect your home during outages, save money on energy, and go off-grid. Batteries can also help homeowners keep more of their solar power on site instead of sending it back through a constrained local transformer. Homeowners interested in storage can explore EnergySage for information about home battery storage options, including competitive installation estimates.
For a fuller look at how utility rules can reshape the math on rooftop solar, these stories offer more examples.
• In California, utilities face multi-million-dollar fines amid a fight with solar homeowners.
• After buying a home, one owner’s first bill hit $420 despite rooftop solar.
• In Ohio, a homeowner learned that half the bill untouched was still possible after solar.
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