Solar Panels

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Solar / PW does not charge EV

Hi All,
I had my solar system and PW turn on in Dec. Since them I have been monitoring what the app shows my home energy usage is and what my electricity provider shows. I noticed that for some days the delta between the 2 is ~15-20kWh.
When I did a deep dive I realized the delta comes when I charge my car. The energy consumed for charging the car is not reported on the home usage on the Tesla app. Moreover I also see that no matter when I charge the energy for EV charging always comes from grid no matter how much solar panels are producing or level of PW charge. On some days I have solar panels producing ~1.5kWh with 100% PW charge and the solar energy goes to grid instead of charging my EV. It is as if the circuit for EV charging is invisible to the solar/PW set up. So I end up paying for EV charging to grid and the excess energy goes to grid for free (no net metering).
I have a 4kW system and 1 PW and Tesla Model 3. Did anyone else also have same issues?

Thanks,
Aditya

Comments

  • It sounds like your EV connection is on the grid side of the system. Not sure if that was intentional or not. For example, I had my AC compressor connected on the grid side. It means I can't have air-conditioning during a power failure, but it also means I don't quickly drain the PWs during a grid outage on a hot day. It's a tradeoff that works in our area (rarely gets above 90F).

    My EV charging is on the Solar/PW side, so I could theoretically charge my EV from the PW. It does require tuning down the EV charging current. As the PWs are limited to 20 amps each, with my 2 PWs, I could go to 40 amps, but that leaves nothing for the rest of the house. Setting the car charging to 16 amps leaves 24 amps for the rest of the house during a grid outage. Tesla added an option to the app to limit how much charging drains the PWs, so it's not as much of an issue as it was last year, where it was likely better to keep the EV charging on the grid side.

    Anyway, every house is wired differently, so what works well for one house, could be quite expensive to change for another house. I happen to have a small subpanel for the compressor that made what I did easy. Moving the EV charging to the grid side would have been more complex and expensive for my specific house.
  • My system went live 12/1/20. At the time of the install the Tesla electricians told me that 240 volt appliances would not be supported by a single powerwall. For that reason, I doubled the size of the system to 2 powerwalls. With 2 I am able to power and backup the entire house. I suspect this is why your EV charger is not being powered by your system.
  • Powerwalls are individually capable of powering split phase 240V AC. I don't know why your installer would tell you otherwise, unless your installation would have the potential load difference of the two phases be greater than 100%. (That's the maximum allowed by a Powerwall.) That could possibly be remedied by moving breakers to different rails in the backed-up circuit e-panel.

    https://www.tesla.com/sites/default/files/pdfs/powerwall/Powerwall%202_AC_Datasheet_en_northamerica.pdf
  • > @srbobc said:
    >At the time of the install the Tesla electricians told me that 240 volt appliances would not be supported by a single powerwall.

    That makes sense although perhaps not exactly true. I would assume your 240 V appliances draw more than 20 amps, which is beyond the limit of a single Powerwall. You could have either a 240v NEMA 6-15 (15 amps) or NEMA 6-20 (20 amp) outlet that could be powered by a single Powerwall. It's unusual to find either of these circuits powering home appliances, and the use of either one might not leave much room for other 120V items in your house.
  • That's very true, TT. My induction cooktop can take over 6kW when on "Boost".
  • Greg,
    Can you comment on the use of induction cooktops ? Currently have a typical cooktop (glass with radiant/resistance coils underneath) that I would consider replacing. Induction efficiency and practicality ? Speed ? Control ?
  • I'll comment as I switched from a radiant smooth top to an induction cooktop 2 years ago. Best appliance I have bought. Feels like it heats 2-3 times as fast, and has very fine control - better than gas. You can melt butter, cook, and then simmer or just about anything else. I'm not sure about efficiency but generally claimed to be 15-30% more efficient. I've never checked those claims. Since the cooktop doesn't get hot, you don't burn overflows onto the cooktop. It still looks new.
  • If the OP turned off the main power from the outside at the fuse box would the power from the solar panels or powerwall flow to the outlets in the house to power the car?
    Or does the power from the solar panels only go to store power in the powerwalls? And then do the powerwalls only supply power to a few outlets in the event of a power failure.

    My neighbor has a generator in case of a power failure. To use it, a cable is plugged into a secondary fuse box panel that that has circuit breakers for lights, stove, hot water heater, refrigerator, etc. You plug the other end of the cable into the generator, flip a switch to shut off the power going to the house, and then start up the generator to power what is on the secondary box.
    He said the generator isn't strong enough to power the A/C so that is why it's not on the secondary box.
    Do powerwall operate the same way in the event of a power failure?
  • @Tesla2018 - Unlike your generator scenario, the Powerwall switches automatically. So when the grid goes out, it disconnects from the grid and powers the house. Most PW owners buy enough PWs to power the entire house, although some items large power items like the A/C could be left on the grid side (that's what I did). I have 2 PWs and powers everything, including EV charging except A/C. There is an option in the app to limit EV charging too so it doesn't quickly drain the PWs. During a power failure, not knowing the outage duration, I reduce my power use to get the most out of the PWs.
  • Tesla Tap: "There is an option in the app to limit EV charging too so it doesn't quickly drain the PWs."

    To be clear, that option on Tesla solar/PV systems is only available for Tesla-branded EVs.

    There are many different brands of EVs in production today. Tesla is but one of them.

    "Blasphemer!"

    ;-P
  • Someone buys a non-Tesla EV? That's heresy :) Good point though.
  • I've been driving EVs continuously since 1997...none of which were made by Tesla...
  • What do you think about solar panel wires?
  • "What do you think about solar panel wires? "

    They're a necessary eyesore. Be sure the contract specifies conduit routing to your satisfaction.
  • > @gregbrew_98470014 said:
    > "What do you think about solar panel wires? "
    >
    > They're a necessary eyesore. Be sure the contract specifies conduit routing to your satisfaction.

    That is what I meant! I researched some information about my question and found this blog https://websolarguide.com/solar-panel-wires/
  • > @morgantiron_98586128 said:
    > > @gregbrew_98470014 said:
    > > "What do you think about solar panel wires? "
    > >
    > > They're a necessary eyesore. Be sure the contract specifies conduit routing to your satisfaction.
    >
    > That is what I meant! I researched some information about my question and found this blog <a href="https://websolarguide.com/solar-panel-wires/">https://websolarguide.com/solar-panel-wires/</a>

    Seems interesting.
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