How many solar panels do you need to charge an EV?

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patrick0101

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#1
To power your EV's energy needs, it depends on what EV you drive, how far, where and how you drive it.
For energy production, it depends on where you are putting the solar panels, angle, azimuth, tilt, shading, and regional weather... There are variables, but with a few tools, you can figure it out.



If you want a rule-of-thumb, here's one:
Each 1kW of panels will get you about 4 thousand miles of EV driving.

Will this be accurate for your home and your Model 3? Nope, it's just a rule of thumb. If you want to get more precise numbers, here's a link that can give you the tools to plug in your car (after it's EPA rated) and your address to get solar energy data for your roof.
 
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chandler
#5
I just have a 4 kW GRID tied system It runs my home and 2 100% Electrics. I normally make 110% of what we use. Last month March I made 506%. My home is very efficient. I use passive and active solar, CREE USA made LED light, 3 Solar SunOvens and ride my bicycle a lot. We live in Super Sunny Chandler Arizona. I added radiant barrier in the attic, more insulation, Solar screens outside and In'Flectors inside all windows.
I have a Tesla 3 on order but will ECO drive it for 300+ miles on a charge. A lot depends on how fast and far you drive. I love 15 mph school zones, I'm the only one doing 14 mph.
 

Topher

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#6
Find out the number of 'sun-hours' you get (Google insolation map). Divide that into the number of miles you TYPICALLY drive in a day (ignore long trips). Adjust that by multiplying by a factor of the Watt-hr/mile of your car divided by Watt rating on the panel.

20 miles on a typical day / 5 sun-hours / day * (300 Wh/mile car / 300 W/panel ) = 4 panels

Adjust that to compensate for various efficiency losses (say 150%) = 6 panels.

Thank you kindly.
 

Bigriver

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#11
I should have started charging a wee bit earlier, as last few minutes had to draw a little from the powerwall.
3564a709-366e-4f31-bea8-04ec70caa073-jpeg.27092

Was an excellent solar day, generating over 75 kWh from my 11.97 kW system. Spent about 25% on the house, 25% to the car, and 50% to the grid, which is banked for next winter.

And @Lovesword, you can rest easy now that my phone battery is back to 100%. 😊
 

Thomajay

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#12
You will love this then. I have a 7.67kW solar array on my roof (I've been selling and installing solar and solar plus storage systems here in central Texas for the past 12 years) and I have an SMA inverter with Secure Power Supply that allows me to tap 2kW of power in the event of grid failure with a dedicated power outlet.

The key here is WITHOUT batteries or any kind of need for a transfer switch.

My girlfriend took a video of me demonstrating this functionality and you can check it out here:

Jay's SPS EV Charging Demo - YouTube

If anyone living in Texas wants to know more about solar, shoot me a note I'd be happy to help!
 

lance.bailey

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#13
[One of] my dream goals is to charge the two EVs from solar. I even get ecited when I get free regen energy form downhill grades. Heck, my kids gets excited when the Tesla shows a green bar for regen.

I like free. It's a Scottish thing, and I'm 90% scotch (by volume) and at least 50% by heritage.
 

PA_Ray

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#14
I finally was able to go live with my solar yesterday, 15.6kw. It is spec'ed to provide a little over 100% of my usage including charging my model 3. That is based on annualized net metering. Bottom line is I should be producing more than I use. It may be a drop in the ocean of what is needed but it feels good and will pay for itself fairly quickly. 9.6 year ROI. My only quandary is whether to apply the car charging savings to my car or the panels. Now that's a problem I hope everyone has to solve someday.
 

Frully

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#15
I finally was able to go live with my solar yesterday, 15.6kw. It is spec'ed to provide a little over 100% of my usage including charging my model 3. That is based on annualized net metering. Bottom line is I should be producing more than I use. It may be a drop in the ocean of what is needed but it feels good and will pay for itself fairly quickly. 9.6 year ROI. My only quandary is whether to apply the car charging savings to my car or the panels. Now that's a problem I hope everyone has to solve someday.
Which has a better interest rate? :)

Awesome install!
 

JDV

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#16
How are you guys able to see the powerflow on your app? I have Tesla solar but I can only see what power the panels are producing. I can't see where it's going to what my house is consuming. Thanks.
 

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JDV

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#17
The question is: Can my solar make enough power to charge my car without tapping into the grid during peak day generation.
I have a 7.6kW system from Tesla. If I plug in my Model 3 to charge a high noon, will the panels produce enough electricity to charge my EV?
I notice that when I do this, the meter still shows that I'm using power from the grid. Thanks for the insight.
 

AEDennis

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#18
The question is: Can my solar make enough power to charge my car without tapping into the grid during peak day generation.
I have a 7.6kW system from Tesla. If I plug in my Model 3 to charge a high noon, will the panels produce enough electricity to charge my EV?
I notice that when I do this, the meter still shows that I'm using power from the grid. Thanks for the insight.
the answer is yes, in all cases, as long as you dial down the amperage of your charge to match your consumption. So, if your production is at 5kW your amps on AC should be no more than 20 amps... (assuming 240V)
 

Ed Woodrick

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#19
If you want a rule-of-thumb, here's one:
Each 1kW of panels will get you about 4 thousand miles of EV driving.
I feel that this is one of the most confusing statements that I've heard in a long time.

To answer your stated premise in the title, one would expect the number of cells needed to support nightly charging.

But rereading your statement, I see that you believe that 1kW of panels can easily charge my car overnight, because I only need 100 miles.
 

gary in NY

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#20
I think it depends on your objective: To charge on 100% solar power, or to offset the EV energy consumption over a given period of time. At the standard 240v 32a level 2 charge for a Model 3, you need over 8kW of power during your max hours of production (note you can dial down the power draw on screen to stay under a lower kW power output system). For a residential system, the house also has power demands at the same time. The above rule of thumb might work if you are looking to offset your usage over a year or so.

My 7kW system can not meet my charging needs without lowering the amps drawn by the car. But I don't charge during the day, so it doesn't really matter. I am offsetting my EV energy consumption, and nearly all of my household energy consumption, via net metering. This is a great option if it's available. If not, batteries may be an option, but you will need several powerwalls to meet the EV charging demand.

It's very easy to underestimate the amount of energy consumed by an EV, particularly when compared to an ICE vehicle powered by relatively cheap and readily available ( and energy dense) petroleum. Add to that the low efficiency of solar panels (in the low 20% range - which coincidentally is about the same rate as a "high" efficiency ICE vehicle), and the limited daily hours of sunlight, and solar alone does not meet all the energy needs of most modern households. At least not without some lifestyle changes which not everyone may be willing to make. YMMV depending upon location.