A western Washington homeowner says a DIY solar project hit an unexpected hurdle before it could move forward, and they want to get it back on track. 

Here's what to know

On Reddit's r/SolarDIY, the homeowner outlined plans for an approximately 21-kilowatt DC ground-mount system using 48 440-watt bifacial panels and two SRNE HEBP 18-kW hybrid inverters listed to UL 1741 SB and IEEE 1547-2018. 

The problem was that the local utility believes the home's 25-kVA pad-mounted transformer is too small and wants an upgrade before approving the system. 

"Export limiting doesn't waive it," the original poster continued. 

Frustratingly, they also said the utility's verbal explanation that it'd pay for the transformer didn't match its written policy, which puts the full cost on the customer. It also wouldn't provide "a ballpark cost" until engineers had the full application, drawings, and spec sheets.

"Has anyone gone through a utility-required transformer upgrade? What did you actually pay for labor and materials?" they asked. 

Replies showed that upgrade costs can vary widely in practice. 

One commenter wrote, "It cost me about $3,100 to go from 25 to 50." Another said, "My out of pocket was only $300 and that included a 50kva transformer plus 2 poles and some wiring upgrades for my neighbors."

More background

Going solar is one of the best ways to save money on home energy, and solar leases in particular can deliver hundreds of dollars in monthly savings without any upfront costs. 

If you want to compare vetted local options, EasyHome's free explorer tool can show what savings may be available in your area.

In this case, much of the discussion focused on a cost that homeowners may overlook when pricing solar: the transformer. The exchange also indicated that changing the approach would not automatically make the issue disappear.

As the homeowner noted, a battery-first setup that connects to the grid would face "the same interconnection process and the same electrical permit as full export," while a fully off-grid version would require separate charging equipment or a generator plus a critical-load subpanel.

"And I'd lose net metering on my summer surplus," they shared.  

What can be done?

A commenter dealing with a rural electric association described a similar situation. They said they "decided to stay off grid" and that it "completely offsets my electric bill (except for the $25 connection fee)," with a return-on-investment of about 11 years.

Some commenters said the hardware configuration itself could also influence the review. One said utilities may care most about "theoretical, rated AC output" rather than panel size and it might be worth resubmitting with just one 18-kW inverter because "21kW DC on 18kW AC is a pretty normal ratio."

For homeowners still comparing routes into solar, EasyHome's free explorer tool can help make the options easier to sort through. It can also help you explore backup battery storage to maximize savings while allowing your home to keep using solar when the grid goes down.

Where can I learn more?

Solar projects can come with utility rules, equipment limits, and surprise costs that homeowners may not see coming. 

• A homeowner who paid $41,000 for solar learned 13 more panels could trigger costly rework.

• A solar owner saw output drop once their batteries filled.

• In California, a DIY 9-kWh setup nearly paid for itself before battery rules hit.

• A DIYer trying plug-in solar encountered app woes and export questions.

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