Model 3

Portable solar panels for charging?

edited November -1 in Model 3
I like to backpack into lakes and often the trailhead will be too far (there and back) for the distance of the Tesla 3 (I have ordered) battery pack. Is there some system available with solar panels that I could carry in the car to add battery charge for the amount needed to get to a charging station or home for recharging. If there isn't something already available this might be a good product for Tesla to offer. Thanks for suggestions.


  • edited November -1
    this has been covered extensive - no portal panels provide enough power to matter - it just won't work

    at 300 watt/hours per-mile you would need a very very substantial system sitting in the sun for many many hours to even add 1-5 miles of range..

    if you're that concerned you're better off carrying a generator and some fuel.
  • edited June 2016
    The battery in that device contains enough energy to take your car an additional 3.5 miles and the solar panel at 30W will give you an additional ~530 yards of range per full day of charging...
  • edited November -1
    think about it another way:

    watts = Volts * AMPS

    a home outlet is 120 volts and 15 AMPs

    but you have to derate the 15 amps to 12 AMPs to allow for continuous load (80% rule)

    so a home outlet produces (give or take because volts will vary)

    120 volts * 12 AMPS = 1440 watts or 1.4 kw

    if you are plugged into a 1.4 kw power outlet for 1 hour you have consumed 1.4 KW/hours

    at 1440 watts divided by 300 wh/mile = 4.8 miles of range for 1 hour of charge - but you have take at least 10% of the loss of efficiency so it's 4.32 miles of range for each hour of charge at 120 volts/12 AMP's
    65 kWh battery would take 45.138 hours to fully charge from a home outlet _BEST CASE_ - and a home outlet produces 1440 watts continuously with very little variation...

    most roof top solar panels are 250 watts under PEAK ideal conditions (peak output mid day) and are far less before peak day and after peak day - it's a sine wave that varies during the day and time of year - 250 watt is the best/most the panel can do - my panels on my roof rarely produce more than 80% of their rating and only for brief periods during the day.

    dimension on these panels are about 5' x 3' (give or take)

    15 sq/ft of panel * 4 panels would be 60 sq/ft of panel space

    if you carry 4 of these roof top solar panels around in your Model 3 you in theory could produce a total of 1000 watts for 2'ish hours during the day if you positioned them correctly and it wasn't cloudy...

    so that would be 2 KWH and let's spot you another 3 KWH for the pre-noon and post-noon production

    5 kwh of production for a 10-12 hour day (June/July -other days of the year will be less - winter will be as much as 50% less)

    5 KWH produced by the panels = 4.5 useable for the charger (10% loss on the inverter) - 4.5 kwh charging the Tesla would be 4.05 KWH added to the battery…(10% loss for the charging)

    that would be 4.05 kwh of charge added to the battery which is 4050 watt/hours / 300 watt-hour/mile = 13.5 miles of range added for a 10-12 hour charge period under _IDEAL_ circumstances

    but you have to carry 4 residential solar panels with you and and inverter and have somewhere to place 60 sq/ft of panel while you're charging the car - and you can't just lay them down on the ground - you'll need a rig to aim the panels to get optimal angle to the sun....

    it's just not practical.
  • edited June 2016
    also I used roof top solar panels as they are the best at the moment - any portal panels will produce "less" watts and therefore the roof top example is the best that can be done - all math represents IDEAL/OPTIMAL solar charging conditions and assume you're charging at the perfect time of day - output of panels off "Peak sunlight" is normally quite a bit less...

    the best roof top panel I found in quick google is:

    at 390 watts - but that is a 5' x 7' panel

    someone can re-run the number - but it will still come up at less than 10 miles a day in the summer for an all day charging cycle.

    With this panel, you get a maximum power output of 390 watts, a maximum power voltage of 49.4 volts and a top power current of 7.92 amps. These modules are constructed to hold 95 individual cells.

    - See more at:

    you'll need at least 3 of them to get to 120 volts to use the UMC that comes with the car - and in theory they could produce about a home outlets worth of power for 1-2 hours day - after that it would be less and the UMC would probably drop off line due to under-volt/under-amp flow.
  • edited November -1
    Each Grape Solar 390W module measures 77.2 inches long, 51.5 inches wide and 1.57 inches deep. Each weighs 78.2 pounds. - See more at:
  • edited November -1
    It works out to a standard panel for an hour (of decent sun) for every mile of range added. You could do a bit better if the was a way to charge the batteries on low voltage DC.

    I don't think it is impossible, but I would feel a bit like Mark Watney. How many pirate-ninjas do <i>you</i> need?

    Thank you kindly.
  • edited June 2016
    Thanks for all the information on solar panels and the difficulty of even a small amount of Tesla battery pack charging. Guess that as a possibility will have to wait quite a few years into the future or the battery density has improved enough to make additional charging in remote areas unnecessary.
  • edited June 2016
    Depends what remote means. Most trailer parks have electrical useful outlets, So you could travel slightly less than half your cars range from the nearest useful outlet.
  • edited June 2016
    RV parks tend to have power for RV's - this is typically a 30 amp or 50 AMP hookup - if you can find an RV park with power you can charge your tesla - I've done it a lot.
  • edited June 2016
    KOA's are my favorite non-Supercharger locations - because there are LOTS of KOA's and they typically have:

    50 AMP hook ups
    don't completely suck as a place of hang out for a few hours.
  • edited June 2016
    I think you would need to buy a Model X to bring enough solar panels.
  • edited June 2016
    Not useful for charging, but for long term storage there is a use case.
  • edited June 2016
    @GALACTIC_III_TSLA, The system you are looking for is called a "rental car".

    Seriously, two suggestions for finding charging resources. First off, many have been added on

    And then for the campgrounds and RV parks that @dortor mentioned, sites like or show most of the campgrounds, and you can filter by which ones have 50A electrical hookups. It's possible to use an adapter to use the TT-30 outlets for travel trailers, too.
  • edited June 2016
    If this were the Jetson’s universe, the car would have a giant folding umbrella solar array—you get to the mall, pop your giant 3000 square foot umbrella high above the parking lot and catch some rays while you and the people parked under your umbrella enjoy the shade :-)
  • edited November -1
    Select the "Mr. Fusion" option when ordering your car.
  • edited November -1
    Quick question (that I’m sure has been asked, but can’t find it). Just had a 22.27 kWp solar panel system installed on the house and will be using Washington State’s NetMetering program. I work from home and usually charge the car at night. Being that the panels are generating power during the day...should I turn off the delayed scheduling and start charging during the day?

    My understanding is that the software in the Tesla somehow knows when peak pricing is, therefore it charges in the late evening or early morning hours when kWh’s are at their cheapest. By charging during the day with solar panels using the NetMetering program, will I experience an increase or decrease in charges per kWh?

    Thanks in advance to anyone who knows anything about this. I have posed this question to both the solar installation company and PSE but haven’t heard anything back yet.
  • edited July 23
    I have a 8gig USB drive plugged into my Tesla Model 3. Every month or just disappears, meaning the Tesla doesn’t recognize that it is plugged in (indicates to install a usb drive to enable honk on demand, etc.). Randomly, it shows up again...but always disappears eventually.

    I know...8gigs isn’t much, and I’m upgrading to a 100gig drive soon. But...does anyone else experience this? If so, is there any way to successfully make it appear and work again? I’ve unplugged it multiple times and restarted the car...but nothing.
  • edited July 23
    I have 5200 watts on the roof with a 4400 watt 220 volt inverter. In good sun I can get 4500 watts, and set the inverter for 2800 watts to charge my mod 3, about 15 mph charging. After sun goes down, must rely on battery pack which is only good for a couple of hours. So portable panels for charging, not really practical.
  • edited November -1
    @Allieroon: I'm in New Jersey, have a grid-tied Solar Power system that dates back to 2008, am under a net-metering program, and haven't paid for actual electricity in years. A $2.50 - $3.50 connection fee a month, but that's it. Even with the Tesla.
    So, the deal with net-metering is like this: You've got your so-called Install date. Call it May 1. In every month, the power company tracks how much the solar system + house deliver to the grid, and how much the solar system + house take in from the grid. The meter that supports this activity is, weirdly enough, one that counts up when energy goes out from the house, but does nothing otherwise, and another meter that counts up when energy comes into the house, but not otherwise.
    So, at the end of the first month, call it June 1, the power company takes the two meter readings from May 1st, subtracts the two from June 1st, and this gives the power into the house vs. the power out of the house over the period May 1 to June 1.
    Subtract the two, energy in from energy out. If the result is positive, the value is the first step in your running balance and you pay nothing. If it's negative, you pay retail for that month and your running balance is also zero.
    Repeat for the next month. If it's positive, add to the running balance and pay nothing. If it's negative, subtract from the running balance. If the running balance is still positive, then pay nothing; if it goes negative, pay up on the negative difference.
    Typical usage is that starting in spring the running balance gets very, very positive over the summer through late fall. At which point, with less daylight, the usage every month is always negative (i.e., you're still making energy, but it's less than what you're using), but the surplus from the previous months is still bigger. If you're unlucky, sometime in February or March your running total will zero out and you'll pay for electricity like all the other peons. If you're like the SO and I you'll walk into May 1st of the following year with a positive net balance. At which point the power company will zero out the running balance, pay you wholesale rates (a penny or so per kW-hr), and one starts all over again.
    So. Now we answer your questions.
    1. Does it make any difference if I charge in daytime or nighttime? Answer: So long as you're on a flat-rate for incoming energy, nope. Net metering in NJ is flat-rate, some 13 cents per kW-hr. And the question of whether one pays at the end of each monthly billing cycle is a question of the net energy usage that month, not whether one used the energy during the day or night.
    2. Now, if Washington State's net metering program isn't counting up kW-hr, but is rather counting up the cost of the kW-hr's flowing in or out, then that changes the equation. If they do that, then the running total isn't in kW-hr's it's in dollars and cents. And they could potentially charge on a time-of-day basis. But, if they're doing that, then they darn well better be paying _you_ on a time-of-day basis, albeit at wholesale rates.
    So, if it's all time of day, all the time, you can still carry forward a balance from month to month, but it'll be in cash. I suspect that, in this case, charging at 2 a.m. when the electricity is cheap would be better than charging during the day/evening when electricity is expensive, and your solar system would make more money for you in that case.

    It gets somewhat different if you have a Powerwall or equivalent in this case, too. A Powerwall can contain several days worth of energy usage, Tesla or no Tesla, so it kind of averages out the energy usage over time. The implication is that, at least during spring/summer/fall, on a daily and monthly basis, there'd always be energy flowing out of your house+solar, but never in, the Powerwall providing the buffer, in which case it wouldn't matter when you charge the car.

    In my case, where the accounting is strictly on a kW-hr running total basis, only, it actually makes no financial sense to even have a Powerwall; it's the net over a month, not the cost on a time-of-day, that matters, and the Powerwall doesn't change the net over a month at all.

    Finally: In New Jersey, when they put in the grid-tied solar panel plans for SRECs and all, the requirement was that the solar installers check over the house's energy usage over the previous year to installation. The installed solar panels and inverters were Not Allowed to make more than that amount, using a fancy equation supplied by the State. The idea in general was that at the end of the billing year, the "net" would be somewhere near zero.
    The SO and I were surprised when, out of the 10 MW-hr the panels were supposed to produce, we were sitting at 12 MW-hr, with 2 MW-hr more than expected and in the running total. So we got a hundred or so dollars back, wholesale. And that continued on for the following years. After a couple of years of this I happened to be at some green conference or other, ran into some other solar installers, and kind of asked, "What gives?" They laughed and stated that the State's equation underestimated the generation from the system, and that we weren't unusual in that regard.
    So.. Two extra MW-hr's per year. Before we get charged cold hard cash. Did the math; with a M3, that's some 8200 miles without paying anything for motive fuel. Since a significant amount of the mileage on the car is on trips with Superchargers, well, so far we're still getting back a bit from the power company and still haven't paid retail.
    So, there you are.
  • edited July 23
    I’m also in Washington state. At least where I live, with PSE, there are no peak/off-peak rates; it’s just ~$0.10/kWh ($0.09 for first 600 kWh, $0.11 after that).

    Also: no, the car doesn’t figure out your utility rates and select when to charge on its own. You have to do that. Either just plug it in and accept the default “immediate charge to limit”, or specify a start/end time. Review your power bill for rates, tiers, and peaks.
  • edited November -1
    @Allieroon - I switched a few months ago to charging my car mid-day rather than after midnight. My reasoning is it is better to not charge/discharge the Powerwalls as much to charge the car. Get the solar energy feed directly to the car. I start charging at about 12:30 pm with 16 amps/240, which is enough to have solar still power the house and charge the car. At that time, the Powerwalls are 100% charged too. Here's an article I wrote about it in more detail:
  • edited July 23
    @Allieroon - on the USB drive, it may be overheating. Most consume grade USB drives are not designed to run in hot cars. Some are only designed for 90F, although many go to 140F. Consider the drive itself heats up 10-20 degrees above ambient, and the car interior can get to 150F on a sunny day. So the drive is really trying to operate at 160-170F!

    Only SD Cards are designed for automotive temperature ranges. Here's a list I made of various drives and temperature ratings:
  • edited July 23
    @Tronguy...thank you for that lesson! Very helpful and I feel like I’ve gained some wisdom! Regarding power walls, my in-laws came up with the same reasons for not purchasing them...but ended up doing so after the first year as they live on an island and lose power on what seems like a regular basis. Their power walls keep them afloat when they experience these time for as long as four days! Anyway, I suppose if you live on an island and have that issue and have the funds for multiple power walls there’s that.

    @bp...thanks for your input regarding solar panels and scheduled charging. I did do some digging online last year and found some resources to gauge the best charging hour, which happened to be between midnight and 3am. I’ve been scheduling for midnight but now I’m just going to plug in whenever.

    @TeslaTap...thanks for the input and resources, much appreciated!
  • edited November -1
    @Allieroon: Yup, Powewalls make great battery backup systems and, unlike the ICE types, don't require maintenance to speak of, oil changes, and the occasional engine overhaul. I suppose the batteries eventually wear out, but it's sure not like the old lead-acid approaches.
    I've thought, idly, about getting a Powerwall for the occasional power outage. The last time we had a serious outage was when Superstorm Sandy came through and, with zillions of trees down, lost power for about five days. Although the neighbors across the street, who had bought a generator before Sandy hit, did have power. We borrowed their generator.
    Sandy was kind of an anomaly, though. Hurricanes kind of track up the coast and ram into Long Island or New England around here, or go ashore in Maryland. By the time they get to NJ, if it all, they're usually way underpowered and not much of a threat. Sandy was weird in that it was hanging out in the Gulf Stream, 50 miles offshore or so, stopped, hung a left, and went straight into NYC, blasting portions of NJ with winds that hadn't been seen in a century. This turned on Nature's Pruning Service and all those weakly rooted trees subscribed. By comparison, Long Island, which sticks straight out into the Atlantic, hardly notices when a CAT 1 or CAT 2 hurricane comes through: the area gets pruned every few years and, well, is kind of immune as a result.

    One last thing to mention. In the example, above, I mentioned an "install date" of May 1 for Net Metering. This turns out to be important. On the yearly install date, the running balance gets zeroed out and one starts all over again. So, suppose that your date was, say, December 1. Yes, you'd get a check from the power company; but with short days and all, you'd be paying retail from that point on forward until the sun started staying in the sky longer; lather, rinse, repeat, year on year. Likewise, one would rather have the saved-up energy ready to go when winter rolls around, so an "install date" of August 1 isn't that great, either.
    In NJ, we're allowed to change that date, once, never mind when the equipment was actually installed. Most people pick April or May, allowing one to build up a surplus for when the snow begins to in late fall.
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