Home Vehicle Charging with lots of solar panels and net metering question.

[K6CCC]

because here (Downeast Maine) if the power can't be fed back into the grid, it just goes (I guess) to ground.

More likely the inverter (or inverters) are commanded off. The reason is that grid tied inverters are dependent on the utility power for a frequency reference (the inverters MUST sync to it), and more importantly, they always operate in max power mode - in other words, they generate as much AC power as they can based on how much DC is available from the solar. If there is no place for that power to go (since you can't export to the dead grid), the inverters shut off. They have no ability to regulate power delivery based on the local load.

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[TaxmanHog]

the meter is only showing me a snapshot number that represents the state at that current time. Sometimes when I'd see it it shows net what I would expect (as it cycles through other number), other times it is showing what is coming in from grid as it adjusts based on whatever the current is coming from solar, etc.

After I left the house to do errands, your situation was in the back of my mind, figured you may have a new fangled meter with the digital display that cycles every 30 seconds or so showing, voltage, amps, KW peak, KWH cumulative, etc then loops.

 

[Yellow Buddy]

I figured I'd try asking this question here first since it is about my F150 Lighting.

When charging my lightning (up to 90%), I'm drawing roughly ~15KW. I have 41 solar panels that can max generate as much as about 12-13 KW but that of course is only at peak times. I average about 7-8KW over the course of the year. More than enough to "net out" and come out ahead in terms of billing, but not enough to charge my truck directly from just solar panels only.

(I'm aware of course that in theory I could turn down the charge rate in my app, though it's been debated a lot here whether that actually works or not, and besides it would also slow down my charging anyway).

So whenever I'm charging my truck, I'm pulling from the grid basically always, and according to my meter as noted that's ~15K. Here's my question. . .where does my solar power go in that case? Is it even getting used/somehow dropped? Is it still powering the other parts of the house, or is it just getting fed back down? I can see that if say I turn on my microwave while I'm charging my truck, the meter goes up to ~16K. But if this is during the day I'm still getting the suns rays but I don't see that applied on my meter really at all. According to my solar provider, once you go above the threshold for whatever your panels provide, you're pulling from the grid which makes sense to me but like I said. . . where does the power go that's still coming in after that mark has been hit? What am I missing? I'm pretty sure it's not a case of say solar bringing 7K, and grid bringing 15K b/c if that were true then the truck would show that's it's charging at a rate of 22K, which is not what's happening. . .

I have 45kW of solar, I generated just shy of 50MWh of energy last year.

For me, I’m net metered. The solar flows to my panel and feeds electrical usage. If my usage is under, it back feeds the grid and the electric company spins the meter in reverse. If I’m not generating, I pull from the grid and the meter spins the other way.

Another words, it’s not going to your truck first. It’s being distributed. Some of it goes to your truck, some of it goes to other places in your house, some of it goes to someone else’s house.

 

[SDSean]

Sorry, can't help you with San Diego Graft & Extortion.

Indeed, hence why I'm basically going off grid in the city. . .crazy expensive

 

[SDSean]

After I left the house to do errands, your situation was in the back of my mind, figured you may have a new fangled meter with the digital display that cycles every 30 seconds or so showing, voltage, amps, KW peak, KWH cumulative, etc then loops.

Yes exactly. . .

 

[SDSean]

I've wondered about that, too. My panels generate more than 10 KW, but the output gets "clipped" at 10. Also, if we lose power, I assume the panels continue to generate (if it's sunny), but my Generac generator kicks in, because here (Downeast Maine) if the power can't be fed back into the grid, it just goes (I guess) to ground. I am planning to put in a battery backup. That way, I can shift to it when the power goes out, and the panels will keep the battery charged...less waste. I have yet to find an answer to the clipping question, though...will the extra energy (over the 10 KW line) also charge the battery?
Tesla, by the way, does let you lower the charging level. Not sure why Ford engineers didn't include that feature in the Lightning. I charge my truck during off-peak hours, to cut the cost. In the summer, it's covered by credits, but in mid-winter the panels don't produce much or long.

You can adjust how much the charger tries to pull in theory though there's a lot of debate on whether or not that actually works. I probably will do this if/when I add home batteries so that I can stay away from the grid as much as possible. . . .

 

[SDSean]

Also thank you all for the input, it was very helpful even though I know I wasn't really asking directly about my truck.

 

[TomAHawk]

If you pair an Emporia EVSE with their energy monitor, it will automatically limit the charge rate to the excess solar being produced.

I would agree with this statement with one caveat. If you have the emporia power monitoring and the Emporia Level II EV charger, you can set it up to charge your Lightning with excess solar. There are a few hurdles you have to jump through but Emporia support is more than helpful when setting this up. I personally use it for my 2024 Lariat. I basically charge it up for free. I would add that if you use pre-conditioning it's not fully automatic. Reach out to me if you have any questions and good luck.

 

[hturnerfamily]

SDSean, one question you had a concern about was what happens to 'unused' solar power:

no matter how you generate power, there is no way to 'save' it, if you don't USE it - unless you have a huge battery bank. The battery bank is then 'saving' your generated power, well, until it, too, gets 'full', and, well, there again, your generated power continues to get 'lost'... it may seem like a waste.

so, if you are attached to the grid, and your truck's amperage draw is effectively requiring it's full draw from the grid, whether for equipment, electronic, or utility reasons, even while your solar panels are generating mid-day power, that solar power, if not used for some other need, is simply bounced back into the atmosphere, just like it is in every other aspect of life, whether off the pavement, off tree leaves, off your roof shingles, etc.

we think about some things as 'waste', but solar power is never ending, and will not change just because we can't make use of it at that very moment - the sun will not stop. The sun does not get tired. The sun doesn't care how 'much' of it's energy we use, or can use. There is no waste.

 

[RickLightning]

Is your FCSP derated? I thought it could supply ~19kW.

240 x 80 = 19.2kW - 7% loss = 17.9 at best.

Many intelligent EVSEs provides the gross electricity in their app, and then FordPass shows the net the truck is receiving.

 

[Maquis]

SDSean, one question you had a concern about was what happens to 'unused' solar power:

no matter how you generate power, there is no way to 'save' it, if you don't USE it - unless you have a huge battery bank. The battery bank is then 'saving' your generated power, well, until it, too, gets 'full', and, well, there again, your generated power continues to get 'lost'... it may seem like a waste.

so, if you are attached to the grid, and your truck's amperage draw is effectively requiring it's full draw from the grid, whether for equipment, electronic, or utility reasons, even while your solar panels are generating mid-day power, that solar power, if not used for some other need, is simply bounced back into the atmosphere, just like it is in every other aspect of life, whether off the pavement, off tree leaves, off your roof shingles, etc.

we think about some things as 'waste', but solar power is never ending, and will not change just because we can't make use of it at that very moment - the sun will not stop. The sun does not get tired. The sun doesn't care how 'much' of it's energy we use, or can use. There is no waste.

Exactly.

The way I think about it is to consider an illuminated solar panel as if it were a battery. If you don’t draw any current from it, it outputs no energy. When you lose the grid, the inverter simply shuts off and no electrical power is drawn from the panels. There is no power “going to ground” or anywhere else.

 

[Rainor]

I'm not making it complex. . . I'm simply telling you all what's happening.

It's noon in SoCal. I know that I'm "receiving" 10-13 KW from my 41 solar panels.
I plug in my truck to charge, which according to the Ford app is pulling in 15.6 KW.
My power meter also says I'm pulling in roughly 15.6 KW from the grid. . .

Where does the 10-13 KW from my solar panels go. . . ? To the ground? To heat? Partially back to the grid?

You're trying to tell me that it goes to the main panel and thereby into the truck, but I'm saying if that was true then the meter would not be reading -15KW and the meter could not possibly equal the same value as what the truck is charging at. . .

Yes it's all one meter I should add. . .

What’s your house load? It looks like:

(15KW Truck + (house load)) - 10KW PV production ~= 15.6KW

It appears house load demand is pulling 10.6KW grid power needed to run the house, which is kind of high. To pull this you’d need an electric dryer running, or electric hot water heater while a few mini-splits are running at the same time.

I have a fully grid-interactive solar inverter 16.5KW. As everyone says, the math is very simple. The excess solar is sent back to the GRID never ground and probably not to a dump-load in your case.

If your HOUSE+TRUCK demand exceeds PV demand, the GRID fills the gap.

Check your average home-load peak demand (Not counting your truck energy demand).

Ultimatly you won‘t care with net metering. It will all average out by end of month anyway.

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