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Expanding Your Solar System Under NEM 2 In Sonoma County

Updated: 3 days ago


Over the years, many customers have asked; “I have a large true up bill, can I expand my solar system?”.  Even if expanding the system made sense physically, often it did not make financial sense as the customer would likely lose their “grandfather” agreement from PGE.   What is grandfathering – in most cases when a customer buys a solar system, they are guaranteed a 20-year period that they could count on to remain on the then current NEM program being offered.  This grandfathering offered protection for a customer to be able to re-coop the cost of their investment by getting close to retail rates for exported power (see the history of NEM).  One of the downfalls of this grandfathering is it can be lost if a solar system is expanded.


A few exceptions to this rule was a customer could add storage to a solar system without triggering the loss of their current NEM.  While adding storage to a NEM system helped off-set some of the costs of a bill, it usually was not justified.  Usually, the primary purpose of adding storage wasn’t financial, but to have backup when the grid was down.  There is an allowance from PG&E to allow less than a 10% increase in solar, not to exceed 1 KW, without triggering the loss of grandfathering as well.  In my experience, this help when we had to replace modules, (maintenance replacements), but was not enough to be cost effective.


Currently in the world of PG&E’s newest program, residential Net Billing Tariff (NBT), we lose up to 75% of the retail value of exported power (wholesale rates).  For this reason, maintaining existing grandfather of NEM (retail rates for solar exports) is more important then ever.  When we design systems for NBT we almost always propose a battery system, either savings or backup, since it makes sense to minimize exports of power (excess power is stored in the battery).  One good thing that came from NBT is PG&E now allows us to install non-export systems for existing solar customers, and the existing legacy system does not lose NEM grandfathering.  First let’s define what is a non-export system, how these systems are designed and then what are the use cases where they make sense. 


A non-export system, while it can be solar only, usually incorporates storage into the design.  These systems use a power control system (PCS) or metering devices that prevents solar from this new system to be exported to the grid.  Thus, in designing these systems we look at the typical day time loads that can be offset directly by solar (including charging the storage device) and the evening loads that can be covered by the storage.  One of the greatest benefits of this design is it allows up to 100% of the legacy systems solar to export to the grid at its current NEM.


There are three ways to do this:


1)        Non-export with PCS (CT meters)

2)        Using a NGOM meter from PG&E

3)        Adding a new Sub-panel for specified loads.

Non Export Systems, Santa Rosa solar company, Sebastopol solar, Tesla Certified installer

In the first design, we put CT meters on both the export side of the legacy system and on the load side of the house, The Power Control System (PCS) then limits the power being exported by the new system to the electrical load of the house.  In this configuration it is possible for 100% of the legacy systems power to be exported.

Non export solar system design in Santa Rosa and Sebastopol, Tesla Certified Installer, Enphase Certified Installer

In the second design we use a NGOM (meter) provided by PG&E.  It can be used with existing solar with storage with a few limitations. The NGOM guarantees exports never exceed what the legacy system produces.


Non export solar system design in Santa Rosa and Sebastopol, Tesla Certified Installer, Enphase Certified Installer

And the third design is to install a sub-panel, that also has the new solar and storage system connected to it.  If a customer is installing many new electric loads like an electric car, pool, additional housing electric heat pump etc. this may be the best approach.  This could also be used if a customer is wanting to have a new protected loads panel (PLP) for a back-up system.  By placing all required loads a customer wants backed up when the grid is down, these loads could also be part of the new non-export system.


So, what are a few general guidelines for when a non-export system makes sense.

1)        If you have a PG&E true up bill of roughly $1,500 or more (remember to include not just PG&E but also Sonoma Clean Power).


2)        A customer is fuel switching, moving from fossil fuels to electric devices like:

a.        Electric cars.

b.        Electric heat pumps (for heating and cooling air and water).

c.        Changing to induction stoves

3)        Other property changes:

a.        Adding people to a property.

b.        New Medical Equipment.

c.        Adding pools, hot tubs, or ponds (pumps and heating).

d.        New ADU’s – additional dwelling units.


With any of the above options it can make sense to add a non-export system to your property.  Often when I do analysis for customers, they wonder why their bills are still so much even though they have solar.  Many systems designed for residential were not designed to zero out a customer but to off-set only a portion of the bill.  As they add new loads, for example an electric car and a hot tub, bills begin to climb from the original sizing.   This is why I  often hear customers say I am paying PG&E about the same as when I installed solar.   – let’s look at one example of how this can occur.


sonoma county PG&E rate hikes, Solar Company Sebastopol, Santa Rosa

A customer had a $250 bill back in 2020, and their system was designed to off-set 75% of their bill.  So, the solar would off-set about $188 and the customer would still have a bill of $62.  With PG&E rate increases, that 62 bills would be $102 by 2024 (65% increases).  If this solar customer buys an electric car in 2024, driven 1,000 miles a month (333 KWH per month * $0.479 per KWH) this would increase their bill $159 or about $261 per month, roughly the same as when solar was installed.  As a point of reference if this customer has not had solar installed, their bill in 2024 would be roughly $571 per month.


In summary, Net Export Systems (NES) offer us a new club in our bag to reduce our every increasing cost of PG&E without losing the grandfathering benefits of our initial solar system.  NES provides us with a way to keep our PG&E costs in check as we migrate towards electric appliances and vehicles.  With the Federal Tax credit still in full swing and ever-increasing utility rates, now is the time to continue taking control of your energy future.

Reach out to Dylan if you have any questions or are interested in expanding your system.


Dylan Mathias

Owner, First Response Solar


License #: 1039876




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