The short answer
SB 868 doesn't stop a solar owner from adding a plug-in kit. It also doesn't say what happens to your net metering if you do. The law is silent on NEM. The Legislature saw the problem and left it open.
In the Senate floor analysis, the Legislature says plug-in kits are "also targeted to customers with existing rooftop … systems subject to NEM tariffs," and that "such a use may fall into a gray area, as the utility's interconnection agreement required for NEM systems may not allow such use."
PG&E and SDG&E asked lawmakers to "clarify that these devices are not eligible for net energy metering" and to bar existing NEM customers from using them. The signed law includes neither. Utah's plug-in law, by contrast, says outright that kits are outside net metering. California's doesn't.
The rule that could cost you your legacy rate
PG&E's NEM 2 tariff lets you change your system and keep your 20-year legacy period, provided the change doesn't increase it by more than the greater of:
- 10 percent of its nameplate rating when first interconnected, or
- 1 kW.
| Your rooftop system | Allowance (greater of 10% or 1 kW) | Full 1,200 W kit fits? |
|---|---|---|
| 4 kW | 1 kW | ✕ |
| 8 kW | 1 kW | ✕ |
| 12 kW | 1.2 kW | ✓ |
| 15 kW | 1.5 kW | ✓ |
PG&E's NEM 1 and Net Billing (NEM 3) tariffs have the same limit. Under NEM 2, a bigger addition has to be interconnected separately as non-export. Otherwise the whole system moves to the current tariff. We checked PG&E's tariffs only. SCE and SDG&E publish their own, so check yours.
Here's what that means for plug-in kits:
⚠️ Two things nobody can answer yet:
- Does a plug-in kit count toward that limit at all? SB 868 exempts kits from "all interconnection requirements". The 10% rule is a term of your NEM tariff, not an interconnection rule, so the exemption doesn't clearly reach it.
- What will the CPUC decide? Its open interconnection rulemaking (R.25-08-004) lists both plug-in solar and "non-export, non-NEM additions to existing NEM systems" as questions in scope.
If your legacy NEM rate is worth a lot to you, wait for your utility or the CPUC to say how kits are treated. If you buy anyway, a kit of 1,000 W AC or less stays inside the 1 kW allowance, if kits turn out to count.
Will it even save you money?
This is the question most guides skip. A plug-in kit saves money only on power your home uses at the same moment the kit produces it.
A solar home on a sunny afternoon is usually already exporting. Any extra production at that hour goes straight out through the meter, unit for unit. So a plug-in kit on a solar home mostly adds to your export, and whether you're credited for that export is the open question above.
- Most useful: your roof system was sized years ago, and you've since added an EV, a heat pump, or more people. Now you buy power in the daytime.
- Also useful: the kit faces a different way from your roof, such as west for late-afternoon sun after a south roof has faded.
- Least useful: your roof already covers your daytime use with plenty to spare.
Check this before you buy
- Look up your tariff. Your bill says NEM 1, NEM 2, or NBT, plus your interconnection date and system size.
- Work out your allowance with the greater-of-10%-or-1-kW rule above.
- Find out whether you export at midday. Download your utility's hourly usage, often labeled Green Button. Hours with negative usage are hours you were exporting.
- Ask your utility in writing how a plug-in kit affects your NEM status. Keep the reply.
Already have solar on the roof?
Before you buy a plug-in kit, find out whether your house is already sending power to the grid at midday. If it is, a plug-in kit mostly adds to that export instead of cutting your bill. The WattHacker monitor shows your rooftop production live, panel by panel. It plugs into the SunPower or Enphase gateway you already own.
- Home use is shown too where your system was installed with consumption meters. Without them you see production only. Your utility's hourly usage download also shows export.
- A plug-in kit is a separate inverter. Your rooftop gateway will not count its production, so neither will we.
- Free to see your panel data, with no subscription. The monitor is a one-time purchase with a 30-day money-back guarantee.
Still have questions about your own system? I'll go through it with you — your panels, your bill, and what's worth doing about it.
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Common questions
Will plug-in solar affect my NEM 2.0 status?
Nobody can tell you yet. SB 868 says nothing about net metering. The Legislature's own analysis called plug-in use by NEM customers a 'gray area', PG&E and SDG&E asked for NEM customers to be barred from using these kits, and that request did not make it into the law. The CPUC has a related question open. Until it is settled, assume adding a kit could be treated as a change to your system.
What is the 10 percent or 1 kW rule?
PG&E's NEM 1, NEM 2 and Net Billing tariffs each let you modify your system and keep your legacy period, as long as the change doesn't increase your system by more than the greater of 10 percent of its original nameplate rating or 1 kW. A bigger addition must be interconnected separately as non-export, or the whole system moves to the newer tariff. Whether a plug-in kit counts toward that limit is not settled.
Is a 1,200 watt plug-in kit over the 1 kW limit?
It is larger than 1 kW. For any rooftop system under 12 kW, the allowance is 1 kW, because 10 percent of a system under 12 kW is less than 1 kW. So if a plug-in kit counts toward the limit, a full 1,200 watt kit would exceed it on most homes. A kit of 1,000 watts AC or less would not. Again, whether it counts at all is the open question.
Will a plug-in kit save me money if I already have solar?
Often less than you'd expect. A plug-in kit saves money only on power your home uses at the same moment it is produced. On a sunny afternoon a solar home is usually already exporting, so most of the kit's output would go straight out to the grid, and the law doesn't say whether you get paid for it. It helps most on homes whose roof system no longer covers daytime use.
Will my SunPower or Enphase monitoring show the plug-in kit?
No. A plug-in kit has its own inverter, which your rooftop gateway doesn't know about, so it won't appear in your production figures. Your utility meter will see its effect as less power drawn from the grid or more sent out.
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