Replies

1. Expert Member
   BILL WICHERS | Nov 03, 2019 10:02am | #1

   It doesn’t really work like that. Think about all of the power — both grid and solar — as a “power pool”. When you charge your car, you draw power out of this pool. You can’t think of each electron as having come from any particular source.

   If you charge your car during the day, and you produce more than you consume, then your car is basically charging with solar energy you produced. At night, it’s the other way around. Your solar system IS contributing to your car charging while it’s producing, the power doesn’t “go to the grid first”, it just goes wherever it’s needed. Grid tied is usually the best all around option for home solar installations, and is certainly lower maintenance than an off grid system.

   Bill

2. 
   caliberger | Nov 03, 2019 10:36am | #2

   Thanks Bill. I suspected that was answer
   Just trying to avoid laundering my energy production through the utility company

1. Expert Member
   BILL WICHERS | Nov 03, 2019 05:37pm | #3

   There is no “energy laundering”. It works like this:
   If your solar system Is producing 3kw, your house is using 4kw (in total including your car charger) and your car is charging with 3kw, then your net load on the grid is 1kw. You can think of it as the solar system “canceling out” the load of your car from the grid’s perspective.

   If your solar system is producing 2kw, your house is using 4kw, and your car is charging with 3kw, then your load on the grid is 2kw. Essentially half of your home is powered by your solar system with the grid covering the shortfall to meet your needs. You can think of it as 2/3 of your car is being charged by the solar system if you want. The electricity doesn’t care where it came from, but you can visualize the system however you want.

   If you have a net metering contract, you could potentially have a situation where your solar system is producing 5kw, your house is using 4kw, and your car is charging with 3kw. You are producing 1kw more than you are consuming, so the “extra” 1kw is going back into the grid to help feed loads outside of your own home.

   In no situation does power ever go from your solar system, to the grid, and then back into your home to power loads within your home. Sometimes net metering is said to be “using the grid as a battery”, but really you’re using the grid to time-shift your energy around. What happens is that maybe during the day your solar system is producing 5kw but you’re at work so your home is only using 1kw, and your car is parked at work not charging. The extra 4kw is sent to the grid to power loads outside your own home.

   You get home late, your car needs a charge, and you solar system isn’t producing anything since it’s night time. You plug your car in to charge, turn on some lights, with the grid powering everything. Now maybe your home is using 5kw, with your car using 3kw to charge, but your solar system isn’t producing anything at all, so the grid is supplying your entire home’s energy needs.

   In that last case, during the day your solar system reduced the load on the grid about the same as your load now at night time. Your solar system still contributed the same amount of energy, but the grid effectively shifted that production in time — you offset the need for other generation during the day, but used power at night. Load on the grid is highest during the day on weekdays, so your solar system was acting as what is known as “peak shave”, providing a little extra power at the time of highest load on the grid.

   I’ve simplified things a bit, but that’s basically how everything works.

   Bill

3. 
   joenorm | Nov 04, 2019 08:51am | #4

   The answers above are certainly how to think about the electrons in a grid-tied system. As has been stated, they go where they're needed.

   That said, Solaredge makes a grid tied inverter with an integrated EV Charger. I think this is about as close as you'll come to what you're asking about, even though it will still act the same way as how the electricity has been described above.

   https://www.solarpanelstore.com/products/solaredge-se7600h-us-inverter-plus-ev-charger?variant=18342575702105&currency=USD&utm_source=google&utm_medium=cpc&utm_campaign=google+shopping&_vsrefdom=adwords&gclid=Cj0KCQiAtf_tBRDtARIsAIbAKe0_-h62XiwjaASHLf63g39Q5dK0VQbDG6XarpAiBL8WLdNOnZACg1QaAhdXEALw_wcB

   I have never installed one of these, and am not sure if I'd recommend them (keeping two tasks separate is usually a better idea). But the idea is pretty cool nonetheless.

4. 
   Jon_R | Nov 04, 2019 10:11am | #5

   Expect to see more non-net terms and demand charges. Ie, 1kWh into the grid won't offset 1kWh from the grid, even if they are close in time. With this, it will be important to adjust load (eg EV charging rates) to match solar production. A monitoring system plus communication to a smart charger can do this, avoiding sending power to the grid. Perhaps the same will be done for air-to-water heat pumps heating/cooling a water tank. Similar load modulation concepts apply to off-grid situations.

5. 
   tommay | Nov 05, 2019 12:06am | #6

   Install a 220 volt breaker in your panel and run it to a charger outside that you plug into your car....the juice you use comes from the solar you have. It either goes into your car or out to the grid.