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Plan with solar panel, does it work or make sense

Discussion in 'Tesla Energy' started by mattack4000, Nov 4, 2019.

  1. mattack4000

    mattack4000 Active Member

    Oct 1, 2017
    Here is my situation. I have a newer efficient house with a small 2kw Sunpower system. The system connects to my 200A panel with a 100A subpanel basically running everything in the house outside of the EVSE, AC and fire alarm. Since I am not producing enough electricity, I have to basically buy from PGE but I do net meter. Tesla (and many other installer) already said they won't touch the current system but they would run a system in parallel. Instead of just adding their basic package, which I believe to be about 2.8kw. I actually have this idea and I am not sure if it will work. THe current system faces SW and the new system would face NE

    1. I will leave the current system to net meter with PGE.
    2. With all the wild fires that are going (Tesla did force me to sign up with one too), I am thinking about 1 backup battery. I know the battery would not be able to charge my cars or keep my AC running. I am perfectly fine with that.
    3. Since a battery will basically kill my net metering, it really doesn't make economic sense.
    4. I am thinking about routing the electricity from tesla solar to the battery and subpanel only. The panels should produce more than enough daily to charge the battery in full and provide all the power to the house. I don't know if the gateway would allow power to be full from the main panel if I need it. I am pretty sure i am not allowed to pass the power back to the main panel since it would result in net metering?

    PGE is changing their peak pricing to I think 4PM-12PM and off peak from 12AM to 4PM. I forgot the exact tiers are, but it's around there.
  2. Late2theGame

    Late2theGame Supporting Member

    Apr 26, 2019
    I have no idea why you are under the impression that a battery would kill net metering?

    We were in the same situation beginning of this year. We had a 10 year old solar system and wanted to add more solar (due to new EV) and powerwalls for backup. We settled on 2 powerwalls for simplicity of install as we could back up almost the whole house and did not need any rewiring inside the house.

    We remain on NET metering - NET2 instead of NET1 because we added more than 10% solar - PG&E rules -sigh. But there was never any discussion of not having NET metering covering both systems.

    The production of both solar system fall under net metering and the usage of the batteries does not affect the rules or rates in any way. We are also with PG&E. The new solar system is installed with its own inverter parallel to the pre-existing one and both can feed the powerwalls simultaneously. Both are monitored by the included neurio-system and my Tesla app shows the combine solar production.

    BTW: Rule of thumb for number of powerwalls is each PW increases max size of downstream breakers which are backuped by 30amp:
    1 PW ~30 Amp;
    2 PW ~60 Amp and so on.
  3. mspohr

    mspohr Well-Known Member

    Jul 27, 2014
    I don't think the battery will "kill" net metering unless there is some tariff rule I don't know about.
    Since you have Net Metering and TOU, you can use the Powerwall to provide power to your house during peak times and recharge from solar during the morning. Excess solar power can go to the grid and you get credit under net metering. This gives you an opportunity to save on your electric bill.
  4. miimura

    miimura Well-Known Member

    Aug 21, 2013
    Los Altos, CA
    With the way California utility rules are changing, getting one or two Powerwalls along with your new solar will help your situation. The batteries will charge in the morning from the East facing array and power the house through the expensive evening hours. The utility price in the morning will be very low (Off-Peak) and the East array will generate very little during the expensive late afternoon and evening hours. You seemed to be referring to the new PG&E EV2-A rate plan. Off-Peak is midnight to 3pm. Peak is 4pm-9pm.

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