What can I power with a 100W solar panel?


Hi this is Amy at the altE Store. We sell
a lot of solar panels for DIY off-grid solar projects. Generally when we design a solar
system, we start with your loads, what you are trying to power, and from there you figure
out what size solar panel you need. We’ve got lots of videos walking you through the
calculations . But now we are going to look at
it the other way around, what can you power with a 100W solar panel? A solar panel is
rated by the amount of power it creates at Standard Test Conditions, or STC. These conditions
include the intensity of the sun, 1000 watt per square meter, the angle of the light hitting
the panel directly, the temperature, 25℃ or 77℉, and other criteria. So as they say,
actual mileage may vary, based on all of these factors in the real world. So we generally
reduce the calculations based on the difference between the lab setting and your actual installation.
When a 12V solar panel is rated at 100W, that is an instantaneous rating, if all of the
test conditions are met, when you measure the output, the voltage will be about 18 volts
and the current will be 5.55 amps. Since watts equals volts times amps, 18 volts x 5.55 amps
=100 watts. Watts is like the speed of a car, miles per hour, how fast is it going
at that instant, 50 miles per hour. To figure out how much power is generated over a period
of time, you can to multiply the watts times the number of hours it is running. So in one
hour, 100W x 1 hour=100 watt hours. Again, with your car, 50 miles per hour x one hour
equals 50 miles. Now that we know the math behind it, we need to figure out how many
hours to plug into the equation to determine how much power the solar panel will generate
in a day. How many hours of sunlight that is equal to the intensity of standard test
conditions, which is basically the sun at noon, will the solar panel be exposed to during
the day? The number of hours of sunlight equal to noon is called sun hours.
As you well know, even though the sun is up at 8 in the morning, it is not as bright as
it is at noon. So you can’t just say that the sun is shining for 10 hours, so I’ll
multiple 100W x 10 hours. The hour between 8 and 9 in the morning is probably only half
as strong as the sun from noon to 1 in the afternoon, so the morning hour would probably
only be equal to ½ sun hour. But the days are so much shorter in the winter than the
summer, the number of sun hours would be dramatically different throughout the year. Also, the amount
of sunlight I’d get in Miami Florida would be different than the amount of sun hours
I’d get in Portland Maine. Ugh, this can get complicated. Luckily, some very smart
people have taken decades worth of weather data and calculated out the number of sun
hours for all over the world, broken out by month, and even the tilt angle that the panels
are mounted. So I can look at the charts to see if I have a 100W solar panel, in Portland,
Maine, installed at about 45 degrees angle, on annual average, I’d get 4.6 sun hours
a day. Likewise, if I took that same solar panel in Miami Florida, installed it at a
25 degree tilt, I’d have an annual average of 5.2 sun hours. Just as a little aside,
I want to make sure you see that during the months of June and July, I’m going to get
more power out of that solar panel in Maine than I will in Florida. With Miami being closer
to the equator and Maine being closer to the north pole, the days are longer in the summer
in Maine, and so the sun shines on the solar panels longer. Kind of cool, huh? OK, back
to the question at hand, what can I power with a 100W solar panel? I need to figure
out my worst case scenario, what is the worst performing month that I’ll be using the
panel? Since for this example I’m going to be using it in Maine, during ski season,
I need to figure on December. So how can I squeeze out as much power as I possibly can
in December? By tilting the solar panel steeper so it points right at the low winter sun.
So I’m going to mount my 100W solar panel at 60 degrees and figure on 3.2 sun hours.
I’ll now take 100W x 3.2 sun hours and get 320 watt hours a day in December. Now, as
you know, nothing in real life is perfect, so I have to figure in losses that I’ll
likely incur, such as voltage drop across the wire, dirt (or snow) accumulating on the
solar panel, losses through the charge controller, etc. So I’m going to multiply the 320 watt
hours times .7. I know, that’s figuring on losing about ⅓ of your power. Reality’s
a bummer. I now end up with 224 watt hours of power that I have made with my 100W solar
panel on a December day. What can I do with that power? Well, first of all I need to store
it in a battery so that I can use it later when I need it. So I’m going to use at least
a 7 amp charge controller to manage putting the power into a deep cycle battery that can
be charged and discharged on a regular basis. What size battery do I need? Sorry, that calls
for more math. I have my 224 watt hours that I’m making, and I’m putting it in a 12
volt battery. Because watts divided by volts equals amps, 224 watt hours divided by 12
volts equals 18.6 amp hours. Even though I’m putting it in a deep cycle battery, most batteries
still don’t like being drained down more than half way, so I’m going to make sure
I get a battery that can hold at least twice as much power I will be using, so I’ll only
use half of the power in it. 18.6 amp hours x 2=37.2 amp hours. The amount of power
a battery can store changes depending on the temperature of the room it’s in. If my battery
is going to be as cold as 60 degrees Fahrenheit, I need to increase the size of my battery
by 11% to accommodate the cooler temps 37.2 amp hours x 1.11=41.3 amp hours. I’m also
going to be converting the DC power from my battery to AC using an inverter, and I’m
going to lose about 5% of my power through that conversion, so 41.3 amp hours / .95=43.4
amp hours. Now I don’t know if you’ve ever been in Maine in the winter. But trust
me on this one, the sun doesn’t shine every day there in December. Not by a long shot.
So I need to figure out how many days without sun that I need to store the power for to
get me through those sunless days. Let’s say I need it to last me the weekend without
sun. 43.4 amp hours x 2 days=86.9 amp hours. Great, I’m going to get myself a group 27
deep cycle battery, that’s 89Ah 12V. OK, now, I can finally figure out what I can do
with that power. I can run my laptop that uses 45W for 5 hours. Because 224 Watt hours
/ 45W=4.97 hours. Or I can power 3 of my 10W LED lights for 7 hours, and still have
a little power left over. Or I could make myself a cup of coffee, listen to the radio
while reading a book with a 10W light on for 3 hours, and use my laptop for 2 hours. This
should give you enough information so that you can figure out how to fit this into your
situation. You can change the numbers to fit your area, and your power needs. If you need
a little help, you can go to our loads list calculator to see how much power common appliances
use, and go to our reference page to see some sun hours charts and maps. If you enjoyed
this video, give us a like and a share, and subscribe to our altestore channel to be notified
when we post more videos. Also go to our website at altestore.com, where we’ve been making
renewable do-able since 1999.

100 thoughts on “What can I power with a 100W solar panel?

  1. So how many panels to power a Tesla Megacharger capable of charging one truck with a MWh battery pack every half hour? That's like 48 trucks in a day

  2. Lol, she said, ”reality’s a bummer.”
    Well, that depends on how realistic your expectations are; helpful video though.

  3. I don't know what some people are moaning about. Her calculations are the best part (with the exception of 5% energy loss calc.)and she answers the title question. And…I don't see what her hair has anything to do with the subject.Nor do I think its dated.

  4. I'm curious (don't know if you or someone else can answer) if I have a 100 ah battery and a 60 watt solar panel that puts out approx 5 amps would it be able to eventually put 100 ah back into the battery?

  5. Fix math please so others can understand why their calculations are off. Thank you. Very informative videos on a goal just love. Clean Energy

  6. I think she did a really good job of explaining it – the one I've understood the most so far. She's got a reply to all of you who are making unkind comments at 07:36

  7. For those who can't add 2 + 2, you should have started with "You can't reliably power anything with a solar panel" to get their attention 😉 Solar power can be as fleeting as a child's giggle and must be collected to be USEFUL. But the math haters want an instant answer.

    My solar application is primarily a "Wait until daylight" solar generator (540AH AGM battery bank kept charged by one 250 watt panel on an MPPT controller). It can provide limited pure sine wave power (fridge, freezer, internet, some lights) for 8 to 20 hours depending on the season (the 2000 watt inverter can handle the starting loads with no problem). The gen can power the central heat for a few hours, which gives the 8 hour limit in winter. If the power outage is longer than the solar generator can handle, I do have a couple of gasoline generators. If the outage were to be weeks, we'd drop back to a much smaller fridge and I'd install the other 1250 watts of solar panels.

    I did the math, including creating a spreadsheet that takes into account battery AH, inverter efficiency, wattage and number of hours of daily use of the things I want to power, winter versus summer sun hours and the difference between STC and NOCT solar panel ratings. I KNOW what I can power and for how long but you need a Kill-A-Watt and some math to get there. The Kill-A-Watt is essential, as an "1100 watt" microwave oven may actually draw 1750 watts

    In the case of "Wait until daylight" backup, the depth of discharge is 50%. We only have a few power outages each year, usually for a matter of hours, so 50% DOD is reasonable. There's also a spreadsheet page for long term power outage with the DOD at 20%.

  8. 9:04 minutes saved for you: a lot more every day with a bit of math and some extra expences in batteryes and inverter you could power up two phones, two usb light bulbs ,a usb fan a ,laptop, a small 12v tv for a few hours. But still a good video to watch if you know nothig about solar.

  9. Damn, if she spent even 1% of the money on her eyebrows that she spent on that hair, she'd look a lot better. LOL.

  10. This solar stuff is somewhat ridiculous here in the USA states that have cheap grid power. I can start my car, let it idle (using very little gasoline), and get 70A of charge into my 700Ah battery bank in 1 hour. That is, my battery bank will go up 10% in state of charge (such as from 50% to 60% charged) in 1 hour. To get that same amount of charge would take a fair amount of solar stuff and I can charge on cloudy days or even at night with my system. Since my setup is 12V, I don't even have to change any wiring. I only have to connect my car to any of my 7 batteries using jumper cables and it will distribute the 70A charge, about 10A to each battery. That is super simple and I have tested it several times and it is reliable. When I checked the battery voltages of all 7 batteries after charging for 1 hour and letting them settle overnight, they are almost all identical (within a few hundredths of a volt from each other which in negligible). This setup is for emergency battery backup power so in that sense it is being used differently than a solar system that may be trying to bring down the electric bill lower.

  11. I'm going solar when they can answer that question in a min or so, and when I can do more than charging 5 hrs worth of basic laptop smh

  12. If you just want an answer and don't care how to figure it out for yourself, watch our "Math Lite" version of this video at https://youtu.be/6K5suniHo_M

  13. can anyone pls teach me my controller has only to buttons.. MODE and LOAD.. load is for ON and OFF of the LIGHT. so what's MODE is for??? the number flash in my controller is 00 always.. how to set it up? I have 100w solar panel…and 12v battery and 500w inverter

  14. I am from the old school so what I did is set up 200 watts in my rv and from that point see what I can power up beside there is the charger controller its tell you how much power I am pulling out

  15. confusion-this woman is smart but correct me–your stuff runs off the battery that powers the invertor-all the solar panel does is re charge the batteyr-am I wrong? the solar panel doesnt run anything it only recharges the battery??

  16. Just divide 100 by 6 to know the KWH produced per month in FULL sun. Boom, done. PS: This gal grew up speaking another language ehh?

  17. I wish I could afford to power my entire home via solar power. However, our electric rates are so damn cheap (10 cents/kwh) that it would take two decades to recoup my money. Not worth it.

  18. So you cant run anything off a 100w? The title say what can you run off a 100 w panel you mentioned nothing so are you saying it doesnt run anything?

  19. Probably the biggest variable is number of days without the sun plus your location and what type of solar panels you buy with the inverter system and batteries. I see a host of problems not mentioned that can go wrong and the cost. I do like the off grid idea but major improvements are needed before I crack open my wallet. I enjoy the video for the explanations. Well done ma'am.

  20. Power from a 100w solar panel
    Thanks mam for to advice me to calculated the power
    The lesson give me a open mind refers my mind thank wonderful I will follow mam ad vice
    May God will bless you

    Yes I will follow all your videos it very good

  21. Other than using a different rectifier, is there any other difference to note to these equations in 240v 50hz areas vs 110v 60hz ares?

  22. Im trying to figure out how long i can stand her by how many comments i read before leaving…
    So at 4.2 minutes × 3 comments equals i go elswhere…
    Nice hair

  23. Watts is the constant so it doesn't matter about what the voltages is or the Amps 18 volts would be the voltage that the panel put out to the 12 volt Charge controller, so if you have a 100 watt panel giving you 18 volts would be 5.55 amps and after the charge controller drops the voltage to 12.7 volts (fully charged) from the 100 watt solar panel would be 7.87 amps Charge controller still put out the 100 watts but Battery use 1/3 more wattage to recharge back up. a 100 watt panel will run 10x 10 watt LED light bulbs but the Battery will need 150 watts each time it recharges the battery's it wood be more efficient to use the power from the panels than it would be to charge Batteries. I would say the most efficient way to use Solar Panels Is with Micro Grid tie Inverter ran with a Magnum MS4448PAE in a AC coupling setup which allow you to use the wattage directly to the homes power needs and the Magnum ACDL-40 that will divert extra current to a Hot water Tank or Baseboard heater if Battery's are full and home isn't using the extra watts generated. At a 120 volts AC Using 100 watts would be .8333 Amps so you can see 100 watt divided by 120 volts is .8333 amps The Magnasine Inverter has a PWM (Pulse Width Modulation) Charger that is more efficient that normal chargers. And the micro inverter have a More efficient inverter than most. This setup would draw less power from the grid during the day in peak power billing time and how much would depend on how many panels that are used. Think of using the hot water tanks to heat the home at night and be reheated in the day time hour. Could cut allot of power usage in a home without using a large battery bank.

  24. I have a small RV Park and want to put in a Laundry Room( two washers and two dryers) maybe a soda machine and A/C window unit. the building is a 16×30…do you think I could use Solar to do this?

  25. You can run about 25 watts all day in perfect conditions with very efficient mppt charger and pure sine wave inverter . Its so cheap now to build your own backup , off grid system https://www.youtube.com/watch?v=GO_d9Ek5nXg anyone can do it.

  26. This is a really really good video. I'm an electrician and this is the very info that I tell people when they ask me about solar. I will be directing them to your video for now on. Thanks

  27. Amazing tutorial, totally refreshed my memory from theory lesson days back in the 90's. And she sounds like a fully trained rep.

  28. Here in the US these mathematical explanations makes smoke come out of our ears because we have been dramatically dumbed down with the No Child Left Behind Act. Worldwide academically Poland scored 17th in math while the US scored in 41st place out of the top 74 nations. I guess this is why you no longer hear anymore "dumb Pollock" jokes in the US these days huh?

  29. Sir I really don't understand the calculations but I do get your points. Thanks for the info you share .it teaches me a lot .thank you sir Regards George

  30. hahahah ummm i gave up after 4 mins , i didn't hear one thing you can power with a 100 watt solar panel , what is wrong with people trying to educate the masses , hahahah it can't be done , leave that to religion.

  31. you literally didn't answer the question listed IN THE TITLE OF YOUR VIDEO!!!!! Thanks for wasting 1 million peoples time.

  32. The lab setting and the math varies incredibly from brand to brand and application, throw into the mix location. After doing 3 Boat jobs and a Trailer if you want my advice do the math best you can add 50 Ah. You should be somewhere near. If not keep adding batteries and panels. The more power the better anyway. You can never really over-do it.

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