For you California folks. Upgrading rules.

I have a friend who has a 10+ year old system. He would like to exchange the old panels for newer higher wattage and more efficient ones. Also replace the string inverter. Possibly add batteries to the system.

Can you one that “under the radar” and keep the old net metering agreement?

You can't legally do that without a permit, but you can probably get away with it especially if you stay with the same AC output rating and just let the new panels overpanel it.

hwy17 said:

You can't legally do that without a permit, but you can probably get away with it especially if you stay with the same AC output rating and just let the new panels overpanel it.

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So if you got an inverter that you can limit the sell back to the same under the agreement, would that work?

Danke said:

So if you got an inverter that you can limit the sell back to the same under the agreement, would that work?

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I think not exceeding the kW rating that the utility has on file would help, yeah. I think going DC coupled it's more likely to look suspicious as well than staying with grid tied AC inverters. But this is just my postulation.

The standard rule for CA residential PV upgrades (as I understand it) and staying on same NEM tariff, is increasing system output 1kW or 10%, whichever is larger. The obvious issue is that simply going to10 year newer panels is likely to be 2X the output and without something else, easily 'caught'
Something for homeowner to consider (and I'd advise researching) - what are penalties if caught, even if not exporting more than current inter-connection agreement allows? how far back? [I don't know answer, just advising to do full due diligence on risk/reward profile]

Assuming upgrading, and more than allowed limit (1kW), avoiding new NEM would technically be 'against the rules' [tariff agreement] as noted above. However, with same/similar number of panels (beware new 'standard'/common panel sizing vs that of 10 yrs ago), maybe fly under radar with hybrid inverter limiting grid export to existing agreement sizing. [beware difference in Solar install contract sizing info and actual electricity generation amount listed in PoCO NEM agreement. PoCo is going to know what site has been exporting for last 10 years, and nothing fancy in identifying if site electricity export goes up substantially]
As for batteries, that would be one way to not lose extra production capacity, but we are (hopefully) at an inflection point with much better batteries (solid state, or ??) not too far off... something to consider in terms of timing of upgrade... fingers-crossed than new battery tech will have longer lifecycles

As for a hybrid inverter which would limit grid export... if you read these forums, you'll see plenty of the more DIY friendly/oriented solutions often don't the best track record in software maturity (and therefore features/function, so exporting more than one thinks its configured for). As trying to break rules, such a homeowner would be well-advised to pay a bit more for a rock-solid hybrid inverter to avoid any 'oops'

On the flip side of trying to stay 'under the radar' / break the rules (avoid penalties), if electricity use increased significantly since original system install (ex EV charging at home), and willing to pay for sufficiently sized whole house battery, upgrading entire system with legit re-permitting and going onto NEM 3.0 may not be that bad. Basically comes down to a not-that-difficult ROI calculation (assuming current system has paid for itself already) - I'd go with looking forward for next 10 years... estimate electricity costs using system as is vs new system investment and a 10 year lifecycle cost estimate.
Will newer, larger system pay for itself, or get close enough, that non-financial considerations can 'tip the scale'?
what complicates the calculus is doing a couple of future state calcs... the under the radar sized/configured system, and a legit/permitted/re-tariffed system? For example, does household plan to stay in house for at least 10 years? plan to add additional EV(s), or other natural gas to electric appliance conversions (at some point, ex natural replacement cycle for hot water heater)? I could foresee a where staying under the radar isn't desirable, if one needed more PV panels than could be allowed under existing system tariff agreement (ie not only newer panels, but a bunch more as well) and still might make financial sense. Just something I'd argue to be open to, in general

Dont know what the rules were 10 years ago but if a roof mount things like RSD's and setbacks are required now. And changing electrical, ie bats, without permits can also create liability and insurance issues. Also, when resell occurs, having everything permitted can be very important. Its one thing to throw a couple more panels up, increase 1 kw. Its another thing to do a complete upgrade.

Hybrid with same AC wattage rating, or limited to same.
Higher efficiency/wattage panels in same footprint as old.
The extra production goes to battery, to be used/exported later.

He can get permission to add battery while keeping NEM x.x, so if he had say Sunny Boy, could replace it with Sunny Boy Smart Energy + battery. Or a different brand that takes lower cost batteries.

Once that is approved, swap panels.

City rules may allow replacement of "equipment" without a permit. PV panels are equipment, too!