I currently have solar panels, installed eight years ago by Solar City. It has 14 panels and is rated 3.5kW. Over a one-year time span we produced more electricity than we used. There were four months in the winter when we used more than we produced, but we more than made up for that over the next eight months. Once we bought a Model 3, about eighteen months ago, however, and started charging at home, we reversed that and owed around $400 at true up at the end of the year. We are about to get a Powerwall and I'm thinking that it would be a good time to also add some additional solar panels, as I think a second Tesla may be in our future. The question is how many panels to add on. The company who will be installing the Powerwall is suggesting adding another seven panels. Does that sound about right? Does anyone have any recommendations? How many panels would it take to produce enough electricity to power a Model 3 to drive about 12,000 in a year? How do you go about calculating that?
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How many solar panels for one new Tesla
- Thread starter RobbL
- Start date
How many megawatts does your system produce now per year?
Say 250 wh/mi Average + 10% for charging losses (that includes some phantom drain)
So say 275 wh/mi
275 * 12000 = 3.3 mega watt hours per year.
For reference my 24 Panel 8kW Array produces about 8 Megawatts a year.
But that is in New England (in California with ideal exposure that same system might output 12 MegaWatts)
Your PowerWall will complicate the estimates because it may help things out by handling your own overage.
7 Panels sounds like in the right ball park (50% more than you have).
You could calculate from your bills exactly how much overage you had over the last year. Your $400 might be a good estimate (converted back to kWh you paid for). But you might have had some credits built up and if you started at zero credits a year ago you might have owed more than $400.
ucmndd
Well-Known Member
This.
Basically you want to tell your installer that you’d like to expand your solar to cover an additional 3.3 MWh of usage per year. They’ll size it appropriately given your specific geography, site conditions, etc. Let them do their job.
Federico
Member
If you drive like 15k per year, thats 1,200 miles per month which is equal to 300kw (1kw=4miles) extra, so your Model 3 use around 10kw per day, which can be archived with a 2.5kw system. You need to add a 2.5kw to your current system (8 325w panels additional panels). You may add a couple of more to cover your future Tesla.
It's definitely this. You're trying to give an answer that's like three steps deep into the problem, with skipping past the variables. Don't do that. We can't give you an answer in number of panels. Your particular house in your particular city determines all of these things, like latitude, which determines sun angle throughout the year, weather, which is how much cloudiness there is, which also affects number of sun days throughout the year, what is the angle/orientation/pitch of your roof, etc. etc. So yeah, you need to keep this simple by specifying just an amount of energy you need, and then they have all of the very specific data to calculate how many panels that would require at your site.
Take your power bills for each month that you were charging and then find out the amount of power that you sold to the utility. That will equal, approximately, the amount of power that you need to add.
Another rough metric is to divide the $400 by your average electric rates. At 20 cents, you were short 2,000 kWh.
Seven panels sounds like more than you need. If they pay you for the electricity then it really doesn't matter.
2000/3.5/(7/14)/24 = 47 days for you to get 2,000 kwh w/ 7 panels
2000/3.5/(1/14)/24 = 333 days for you to get 2,000 kwh w/ 1 panel
So if you are only short 2,000 kwh, then you only need 1 panel more.
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