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  • System expansion -SoCal

    hi, i have a 4.56kW -16kW Solarworld + M250 phase system installed in coupe of years back when the NEM plans was pretty favorable . Given our increased energy requirements, we are thinking of adding panels to this system. Couple ofquestions

    0. is there a minimum kW that i can add to this sytem while maintaining my original NEM rate plan ? I heard from one of the comapnies that 1.2kW can be added..but i am not able to find any documentation
    1. Does a new SDGE application needs to be filled and approved along with city inspection for adding these panels (1.2kW)


    any recommendation on installers in San diego to get this done economically ?

  • #2
    SDG & E has information regarding system expansion limits. I'm on NEM 1.0. Last time I checked, system expansion was limited to 10 % of nominal system size or 1 kW, whichever is greater.

    In any case, give them a buzz, or check their website to confirm. My info is deemed accurate but not guaranteed so.

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    • #3
      Thanks. Can you point me to where this information is on the Sdge website. I am not able to find it

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      • #4
        Originally posted by Sparta_SC View Post
        Thanks. Can you point me to where this information is on the Sdge website. I am not able to find it
        Are you on NEM 1.0 or 2.0 ?

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        • #5
          I am no sure. Where do I find this? System was installed in dec 2015..

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          • #6
            Originally posted by Sparta_SC View Post
            I am no sure. Where do I find this? System was installed in dec 2015..
            Best to call SDG & E to make sure. Given the likely Dec. 2015 PTO date the system may have, you're probably on NEM 1.0, officially known as "NEM". The official name for what replaced "NEM" is "NEM-ST".

            On further checking, whether on "NEM" (NEM 1.0) or NEM-ST (NEM 2.0) you can increase your system size up to 1MW (see footnote to para. 7 of sch NEM - kind of confusing), but there are consequences if you increase too much and the consequences are slightly different, but hard to describe and open to some need for interpretation, depending on what you may have done with your billing, inadvertently or otherwise, since P.T.O.

            For NEM, see Cal. P.U.C. Sheet No. 28169-E.
            For NEM-ST, see Cal. P.U.C Sheet No. 28177-E.

            The limits without possibly some bizarre consequences for either are the same, 10% of nominal system size or 1 STC kW, whichever is larger, but be careful. A careful read of those provisions for system modifications under either tariff might be interpreted as saying if you increase system size beyond those limits, you may be required to meter the additional capacity separately, possibly meaning some expensive metering modifications and getting the additional capacity billed under another tariff (and so, maybe not eligible for net metering for that portion of the power generated by the increased system capacity ??).

            Perhaps interestingly, the system modification provisions of both tariffs include the wording: "...and provided the modifications and/or repairs do not do not result in the Generating Facility exceeding the Customer's annual on site load". That may be another issue that's best raised with SDG & E for such things as how "annual on site load is defined.

            You will also need to consider a building permit and any system mods. such as early shutdown requirements that came into force since your original P.T.O.

            Respectful suggestions:
            1.) Read the tariff texts, particularly the sheets listed above.
            2.) Call SDG & E and get the info straight from the source. Get nanes of who you speak with before you begin talking. I've found the folks there to be quite helpful if you get one of the more knowledgeable ones.
            3.) Call/visit the county for accurate info on building permits and system mod. requirements.
            Last edited by J.P.M.; 01-25-2020, 05:33 PM.

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            • #7
              Thanks JPM. Will read through and call them

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              • #8
                In the rest of Califonia they are often referred to as NEM 1.0 and NEM 2.0. I have also heard that NEM 3.0 is in the works. SDG&E seems to have their own unique nomenclature. PG&E also allowed me to increase capacity by 1kW.

                A 1mW increase would most likely require infrastructure upgrade and perhaps a different schedule altogether.
                Last edited by Ampster; 01-25-2020, 04:54 PM.
                9 kW solar, 42kWh LFP storage. EV owner since 2012

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                • #9
                  Originally posted by Ampster View Post
                  In the rest of Califonia they are often referred to as NEM 1.0 and NEM 2.0. I have also heard that NEM 3.0 is in the works. SDG&E seems to have their own unique nomenclature. PG&E also allowed me to increase capacity by 1kW.

                  A 1mW increase would most likely require infrastructure upgrade and perhaps a different schedule altogether.
                  And that's what they're often/usually referred to as in SDG & E territory. I was attempting to be clear and specific. That NEM 3.0 may be in the works seems a no brainer as things do change. What form such changes may take is unknown until approved by the CPUC.

                  Hell Ampster, I'm trying to stay on topic here. Worry about NEM 3.0 if/when it comes along.

                  I'm also not surprised PG & E limited you to the same 1 STC kW or 10 % of system capacity (whichever is greater) increase. It was mandated by the CPUC for all residential systems in I.O.U. territories.

                  I appreciate that the 1 MW reference in para. 7.b. of sch. NEM is bizarre, but sch NEM-ST (NEM 2.0) actually has no system size limits, just extra connection charges required by rule 21 if system size exceeds 1 MW.

                  Sch NEM (NEM 1.0) had a 1 MW size limit. FWIW, I do agree with you that a 1 MW increase would cause some infrastructure considerations but that seems not really something most residential users probably need to worry about (at this time anyway).

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                  • #10
                    Originally posted by Sparta_SC View Post
                    Thanks JPM. Will read through and call them
                    You're welcome. When you do call, be professional and keep your patience, but be persistent.

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                    • #11
                      I have a similar system installed in 2015 up in PG&E Land. I am also on "NEM 1.0".

                      I don't know how easy it will be to expand your system as the limit on one branch of the M250 micro-inverters is 16 - which is what you have already. It won't be as easy as just adding 1-4 extra panels to get 1kW of extra capacity...you would need an extra "branch" and all of the additional changes that would entail. I am just a homeowner so I have no idea if that means a new conduit run, a new breaker, new permits etc...

                      I am posting as I have contemplated doing a future upgrade to my system as the panels degrade, PG&E raises prices, and IF (when) we need more generation...We are looking at getting a second EV, we have added a hot tub that eats a lot of Kw, and due to the recent PG&E changes in rates and minimum billing fees our bill has jumped quite a bit in just the last year...

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                      • #12
                        Originally posted by w00dy View Post
                        I have a similar system installed in 2015 up in PG&E Land. I am also on "NEM 1.0".

                        I don't know how easy it will be to expand your system as the limit on one branch of the M250 micro-inverters is 16 - which is what you have already. It won't be as easy as just adding 1-4 extra panels to get 1kW of extra capacity...you would need an extra "branch" and all of the additional changes that would entail. I am just a homeowner so I have no idea if that means a new conduit run, a new breaker, new permits etc...
                        It may be as simple as pulling another pair of wires and adding a circuit breaker.

                        I am posting as I have contemplated doing a future upgrade to my system as the panels degrade, PG&E raises prices, and IF (when) we need more generation...We are looking at getting a second EV, we have added a hot tub that eats a lot of Kw, and due to the recent PG&E changes in rates and minimum billing fees our bill has jumped quite a bit in just the last year...
                        I am a big fan of over paneling to contemplate future upgrades and or EVs. I am on NEM 2.0 with PG&E have a 5.7 kW SolarEdge grid tie system and recently added 1 kW of panels with microinverters. You will have to evaluate the advantages of extra capacity versus staying on NEM 2.0.
                        9 kW solar, 42kWh LFP storage. EV owner since 2012

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                        • #13
                          For the first 3 years I was right at almost 100% of actual use - by chance really...We bought an EV right as we put up the panels, so we guessed at the "right" size for our system.

                          Since that time, rates have changed a bit, we are charging the EV more at home, and we added a hot tub that is a terrible energy hog...last year we ended up with a $675 true up bill.

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                          • #14
                            Originally posted by w00dy View Post
                            For the first 3 years I was right at almost 100% of actual use - by chance really...We bought an EV right as we put up the panels, so we guessed at the "right" size for our system.

                            Since that time, rates have changed a bit, we are charging the EV more at home, and we added a hot tub that is a terrible energy hog...last year we ended up with a $675 true up bill.
                            How are you heating the water in the tub ? Is it covered when not occupied ? If water heating is by electrical resistance and you have gas service, get a nat. gas heater. Heating water with resistance heating is like cutting butter with a chain saw. Match the fuel's capabilities to the task. If nothing else, you'll likely save $$.

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                            • #15
                              Originally posted by J.P.M. View Post

                              How are you heating the water in the tub ? Is it covered when not occupied ? If water heating is by electrical resistance and you have gas service, get a nat. gas heater. Heating water with resistance heating is like cutting butter with a chain saw. Match the fuel's capabilities to the task. If nothing else, you'll likely save $$.
                              It is a small plug-in patio hot tub running at 120v. It is covered when not being used - however, the old cover is toast. A new cover is on order that should be better than the old cover. This tub is a partially spray foamed version, where some of the pipes are covered and the fiberglass tub shell itself only has around 1-2" of foam on it...so not the best insulation by any measure. Buying a better insulated tub would cost $5000 to $6000 minimum.

                              We do have natural gas, but I have yet to see a stand alone hot tub heated by natural gas that is affordable - I have seen natural gas heaters with installation costs that would be upwards of $1500-$2000 and that might only save us $30 a month...not sure that pencils out.

                              The tub creates a bit of a hum when running the low speed pump to keep it filtered, and more importantly hot. This low hum is very annoying and makes it hard to sleep since the tub is right next to our bedroom - so we are using one of the features built into the tubs smart control panel to always shut it off between 11pm to 7am. This of course means that the only time it will be heating is during the day - and since this tub is configured to run on 120v it doesn't heat up very quickly.

                              We are on time of use for our PG&E electricity, and I hate the fact that if I want to use the tub during the evening I have to heat it during peak times, and if I want it hot enough to use it first thing in the morning, then I have to make sure it is at say 104­° at 11PM before it shuts off for the night - this means the tub is still only around 99° 8 hours later.

                              I have even looked into converting to a small 24hour circulation pump for the unit to make it virtually quiet. If it had a small dedicated circulation pump then it could be setup to also heat at night while we are sleeping at the off peak electric rates...that alone would probably save us a ton of $$$. But I would need to figure out the plumbing and electrical details to add a circulation pump to a system that is not designed for that type of pump.

                              The heater is a 1.4Kw heater at 120v, and some charts I have seen tell me it should heat water around 2.5° per hour. In my case the tub loses 5-7° per 8 hours (overnight), so I need 2-3 hours just to get back to temperature - I don't know what the heat loss is during the day...

                              I have just resigned myself to the reality that a hot tub costs money to run - I think I am averaging $45 a month or so to run it. That is the long story anyway!

                              So, getting back to the original reason for my post - the hot tub, and other items, have resulted in higher electrical use at our home, which has in turn had me contemplating adding a few additional panels to my system, just like the original poster. Since adding new panels would mean at least a new branch circuit I don't know if it would be doable for my setup...the OP's situation may be different. Hopefully my story helps out.

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