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Powerwall and Net Metering?

Discussion in 'Tesla Energy' started by spentan, Oct 28, 2016.

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  1. spentan

    spentan Active Member

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    Hello everyone,

    Have placed an order for 4 Powerwall 2.0s as I have a 12.6kW Sunpower Solar System.

    Wondering what are the advantages of Powerwall/Battery Storage as long as I have Net Metering?

    Can anyone think of any uses apart from Backup in Power Outages?
     
  2. Skotty

    Skotty 2014 Model S P85

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    Insurance against the possibility of regulation changes allowing the utility to end net metering.

    Also allows net metering to work at higher solar market penetration levels for the benefit of those who can't or won't install Powerwalls.
     
    • Like x 2
  3. Brovane

    Brovane Member

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    If your utility has a Time of use plan, you could shift the timing of when you pull from the grid to night-time.
     
  4. electracity

    electracity Active Member

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    No financial advantage with net metering. The only benefit is power backup.

    California will only allow new net metering customers for a couple more years AFAIK.
     
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  5. nwdiver

    nwdiver Active Member

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    We need to work harder to create a benefit to distributed storage... utilities are careful to carve out rates so there's no benefit to storage. Either with production fees or other minimum fees....
     
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  6. outie

    outie Active Member

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    I know this isn't specific to Powerwall 2.0... but do power companies let you store their energy at super low peak rate and export back to grid at on peak rate when you are under the TOU plans?
     
  7. Akikiki

    Akikiki A'-Lo-HA ! y'all

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    For what my two cents are worth, I agree. He who give also can take away. Our utility in HI has stopped new NET Metering. (They say the grid is max'd). Now anyone with solar has to do grid-supply or self-supply (both require energy storage at customer's expense.
     
  8. strider

    strider Active Member

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    Depends on the utility. Here in NE Oklahoma (PSO) it's true net metering. At the end of each month they take the kWh you pulled minus the kWh you pushed. If the value is positive (you used at least some power from the grid) you pay for that power ($20 minimum). If the value is negative (you pushed more power than you pulled) you pay the $20 minimum.

    Other utilities have a buy/sell model where you buy power from the grid at some rate and sell power when you over generate at some rate. Depending on how that is structured there could be benefits.

    In some higher cost areas there's potential rate arbitrage even without solar. IIRC with PG&E I was paying $0.36/kWh peak and $0.11/kWh off-peak. So you could have a powerwall and charge it at night and then discharge it during the day when power is more expensive.
     
  9. Xminus6

    Xminus6 Member

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    Yup. While CA still allows net metering on TOU plans, Powerwalls don't make much sense. If you use solar to charge them they're actually losing you money. The best thing to do in CA with a Powerwall is to only buy as much storage as your house uses during sunlight hours so you can run your house off of energy you buy at night.so that the solar panels can sell ALL of the energy they create during peak hours without having to support the needs of the house at that time.

    So the math for the payoff period for a Powerwall where TOU Net Metering is available is pretty bad. Calculate the difference between your peak and off-peak energy rates. Multiply that difference by the capacity of the Powerwall. That's your financial gain for each day as long as you're able to full discharge your Powerwall during the day when your solar panels are generating at peak rate. For PGE it works out to about $1.40/day. So payoff is somewhere over 10 years, which isn't that nuts compared to the payoff period for a PV system (I know I'm ignoring the time value and opportunity cost of the money spent on the Powerwall to keep it simpler).
     
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  10. Cosmacelf

    Cosmacelf Active Member

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    For TOU net metering, you would charge the Powerwall from the grid from midnight to 5am or so, export all excess solar to the grid during the day, use the Powerwall power from when the sun goes down until it is exhausted, rinse lather repeat. Also, keep like 20% of Powerwall always powered for evening blackouts.

    This gives you full peak rate for all solar energy produced, and allows you to essentially pay super off peak rates for evening peak electricity usage. And you get a free power outage generator in the bargain (once the pay back period is over).
     
    • Informative x 2
  11. dennis

    dennis P85D

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    In the PUC decision reached earlier this year paying new net metering customers at the retail rate for power sent back to the grid was preserved until 2019. Doesn't mean it is going to end then, just that they will have to review it again in 2019 when TOU rates go into affect for all residential customers.

    Once you connect to the grid through net metering your retail rate credit is guaranteed for 20 years from the date of interconnection.

    Inside the decision: California regulators preserve retail rate net metering until 2019
     
  12. AEdennis

    AEdennis Active Member

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    This is exactly my plan (using grid to charge batteries during super off-peak (10pm-8am in SCE) and feedback to the grid off my array, as I do now. Basically, it's like charging another EV during the super off-peak time.
     
  13. miimura

    miimura Active Member

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    From my point of view as a PG&E NEM customer, you can only save as much money with a PowerWall as you currently pay at your annual true-up. If you are currently Net $0 true-up but are a net user of kWh, then a PowerWall won't save you anything. I have a small 4.32kW DC solar system and average about $800/year energy charges due at true-up. Rate arbitrage by either capturing my own solar during Part-Peak or actually charging the batteries during Off-Peak, then using the batteries to avoid any Peak period usage could save me up to that much on my annual true-up. If you interconnect batteries, you have to sign a special agreement. I don't know the conditions of that agreement, so I don't know if you're actually allowed to discharge into the grid during peak period without a signal from the utility that it is needed. Clearly the rate tariffs need to be modernized to fully account for people who have distributed storage and generation.
     
  14. Akikiki

    Akikiki A'-Lo-HA ! y'all

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    #14 Akikiki, Oct 29, 2016
    Last edited: Oct 29, 2016
    Outie, Strider is right about it depends on utility. But buying back power is a function of NET Metering, not TOU. These are two separate programs. If you are a NET Metering customer, you have an agreement with the utility to generate power and sell back to the utility pushing it to the grid. But as a TOU customer, you just buy it and depending on time of day, you pay different rates per kw. You could be both a NET Metering and a TOU customer or just NET Metering or just a TOU customer.

    For instance, here in Hawaii, we have more than one NET Metering arrangement. Some of us are fortunate to sell the power we generate back to the utility at the same rate we buy it from them at night. But just before they closed the NET Metering program to new customers (Oct '15), they also changed it. When they changed it, the utility lower the buy back rate from $ .26 per kw to $ .14-.15 per kw. This means someone wanting to add solar during that time had to increase the quantity of solar by about 40% to break even at the same $$ as those of us that got in early.

    TOU is simply different rates for each kw depending on when/what time of day you used it/buy it. Of course its not automatic, you had to sign up to a TOU plan. Here the utility announced a pilot program to access 5,000 customers to a new TOU rate plan. In less than a week, 5,000 customer had signed up and max'd the available slots.
     
  15. winfield100

    winfield100 Active Member

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    I'm surprised no one has mentioned VPP's (Virtual Power Plants)
    IF you aggregate 1,000 of them, you have a 14 Megawatt VPP (or whatever multiplier) peaker plant, (spinning reserves)
    frequency regulation, etc.
    The utility can decrease its spinning reserves and save money and the aggregators can profit

    University of Delaware, USA, has been doing this since 2011 using ~39 minicooper EV's as a battery bank for EV2G
    UD to partner with NRG Energy to develop electric vehicle-to-grid technology

    Australia this August announced a VPP with about 1,000 or so battery banks aggregated
    A Virtual Power Plant Built With Solar and Storage Is a Blueprint for Australia’s Energy Future

    Tesla Energy will overwhelm Tesla the vehicles
     
    • Informative x 1
  16. ReversePolarity

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    Maybe non related question but is there any sort of change that TOU may go away for existing rate holders?

    My mini solar system generates on average 20kwh a day and I'm using close to double of that, but bill is still $0 thanks to NEM.

    So my choice would either be to get a powerwall to charge at night and arbitrage in the day time, or to install more solar panels, albeit, inefficient due to it being on the morning side of the roof.
     
  17. ecarfan

    ecarfan Well-Known Member

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    I signed that agreement this month, and can tell you that I am allowed to discharge into the grid during the day and do not need any special permission from the utility to do that.
     
  18. miimura

    miimura Active Member

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    Was there anything unexpected or otherwise interesting in the agreement?
     
  19. Ampster

    Ampster Member

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    #19 Ampster, Oct 29, 2016
    Last edited: Oct 29, 2016
    The devil is in the details. I doubt that the agreement allows you to "discharge" battery energy into the grid. It does allow you to sell solar generation to the grid. There is a difference and I doubt that your SolarEdge inverter will sell more energy than the panels produce. As Miimura and Cosmacelf have said, you can offset your critical loads consumption, which will maximize the amount of solar energy that you can sell. I do not believe that you can sell more than your solar panels produce.
     
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  20. miimura

    miimura Active Member

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    As I recall, you have a Radian and are on SCE. Do you have a battery system interconnect agreement or are you exclusively self-consuming your battery energy?
     

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