How Many Solar Panels Do You Need? Follow This Easy Breakdown!
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- Опубликовано: 16 окт 2024
- How Many Solar Panels Do You Need? Finally An Easy Answer!
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Trying to figure out how many solar panels you need is confusing! I found 5 different ways to calculate the number, and none of them were easy to follow. In this video, we'll take a look at the math behind this question and go through it step-by-step with an example to follow.
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This is one of the most useful videos I've seen on this topic. Thank you for unpacking the equation so clearly. Top job.
I am building an off-grid system for my house. During my peak month in December, I used 28 KWH per day. I live in Hawaii, so I put in my ZIP code to figure out number of hours of usable sunlight per day. It is 5.25 hours in December and 6.6 hours in July. I found bifacial Qcell panels that are 455 watts. There's a separate structure built just for solar generation that keeps the lines under 25 ft in length. EG4 18Kpv inverter and battery setup should keep me below 18% system loss. The structure was built to hold solar panels at 21° facing directly south. Accounting for albedo from clouds, I needed at least 9 KW with a 28 KWH battery.
28 kWh for a battery is huge and costly. I would recommend that you try to make do with a ~10 kWh battery, increase the size of your solar array and get a generator for backup. The EG4 18kPV can handle up to 18 kWp of panels. It's just not worth it spending a fortune on batteries as they have a limited lifetime. Panels are a much more durable investment.
I've seen this formula listed on several RUclips videos. What I don't understand is the solar panel wattage figure. For example, the SILFAB-SIL-400 solar panel has a STC (best case) rating of 400 watts, but under normal operating conditions, it's rated for 298 watts. This is basically true for all solar panels. If you use the higher number, it would seem you'd be designing a system that would only produce approximately 75% of what was actually needed...
Everything is derated you never get say 10.4 kw out of a system more like 7.8 if you are lucky
Not an expert by any means, but I’m guessing it’s something to do with “peak wattage vs. running wattage” of what you’re powering with them.
Peak wattage being what is needed to “jump start” the item… a refrigerator or A/C for example, then run normally after that (running wattage).
@@alamomonkeyno, solar panels don’t work like that. Portable generators do, and your explanation fits those perfectly.
@@bradley6609The published rating is best case scenario, like at the equator in full sun on the coldest day they get. The panels have to be derated for latitude (distance from equator) and for cloudy or partly cloudy days. A fudge factor for age doesn’t hurt either.
I should think picking 298 watts would then give you a much realistic calculation to determine the number of panels you know. I have learnt it’s good to go slightly up with panels than down
This really helped with my school project
very good info. going to build a bigger system with solar /grid/battery,. built a 2 panel 100w solar system to charge my battery in my BBQshed last year for the fun ; I still ran 110v to a sub panel to run my refrigerator . thanks so much for the break down
a house with electrical heating only uses 32 kWh per day in Finland. That´s 20 panels at 4 hours of sun per day. I don´t know what upper class American business elite uses 47 kWh per day. I would like to know how to get bare minimum for Panasonic heat pump, floor heating in two rooms, appliances, hot water and lights. Would 16 kWh per day and 10 panels suffice? I would use fireplace too.
I want to power a 1.2 kwh heater + 0,12 kwhheater (these are actual momentary usages) + 2.15 kwh sauna + 0.53 kwh water boiler + 0.62 kwh heat pump + freezer and fridge and others 1 kwh. How much do I use per year if these appliances take 5.62 kwh while running? How big inverter do I need? 6 or 8 kwh? How many panels will this amount to? In the winter we have 5 hours or daylight. In the summer we have 18 hours daylight. How can I send excess power back to the grid and get paid by the company?
It's rare for a 100w panel to average 100w: in addition to the hrs/day not being an average of 12 hours on the equinox (4-6 hrs in summer in the southeast, due to clouds, or it's not getting full sun at 6AM-11AM, etc),
you should also multiply by 85%. because clouds or line losses also make it "only a 100w panel under perfect laboratory conditions".
I'd also go by your worst month (Aug-Sep in south, Jan in north), unless you have generator/microhydro for that month or for special occasions
That's the whole point of the irradiated value. To correct for the amount of sunlight in your location...
Great video, very helpful. Thanks
thank you for the information, was to useful to my
Thank you good reference.
I just want to find out how cheaply i can do 50kwh per day. Im in mid Michigan we have a south/north facing roof with zero shade.
For panel sizing, panels never output their rating, more like 75-85% so I assume if you're really going for 100% offset, you need to use the NOCT values for each panel?
Amazing video buddy!!!
Thank you so much for sharing your knowledge with everybody. Great explanation and easy to understand. Thank you.
Thank you so much. I am an engineer but i didn't get calculate this right myself 😅
Great explanation, thanks 😊
Thank you so much for that formula!!!! That way people don't get under sold or over sold on the necessary equipment.
Great video thanks
The modern panels state that efficiency is around 24%. Shouldn't we take this into account? I mean a panel technical gives 400w but in practice 96w.
That is not what the efficiency means. The panel is rated for 400 watts, so if it has full sun and ideal conditions, it will produce 400 watts. The efficiency is the measure of how efficient it is at converting the total energy of the sun hitting the panel. If it was 100 percent efficient, the panel would output 1600 watts for its size.
A 400 watt panel will only pass 300 watts through the most commonly used micro inverter I have not heard of any micro inverters rated for over 300 so we are basically leaving 25% of the capacity of these big panels unused on the roof for ever none of the sales people ever tell you that do they ?
You're right, I haven't seen micro-inverters that will handle the watt ratings for the higher end panels (yet), so the output will be clipped. String inverters can be used to work around those limits, but then there are other trade-offs to consider.
THANKYOU!!! I have been looking for this and everywhere I go starts with a damm sales pitch and I just want to know how many panels I need, then I'll decide if I want to go to solar or not.
How do you figure that out if it will be new construction.
Here's an article that can help you get a rough estimate: www.energysage.com/solar/solar-101/how-many-solar-panels-do-i-need/?rc=p-tophomeowner
They also make specialized software that can model usage but you'd have to work with an installer.
Nice video...Question: Are those kWh you've plugged into to spreadsheet. I'm asking because I only used ~3,800 kWh all last year based on last 12 mos of data from the power company...So the huge discrepancy in your numbers vs mine makes me question whether I'm using the right numbers...My numbers are from each bill and listed as xxx kWh for the month....so each month on average is about 300kwh per month. That seems WAY too low compared to your numbers and that calculates to about 6 panels (rounded up).
You did not only use 3800 in a year lmfao...you're confused my friend
I think it depends. If you live somewhere where it is not too hot or cold aka S. Cali I'm guessing your bills won't be that high. I live in the desert so if you compare my July bill 2400 kWh vs November 400 kWh there is a huge difference however 3800 does seems a bit low.
I use only 2,000 kWh/year in a two-person household. The numbers in the video are USA numbers, most people in the world use only a fraction of what Americans use.
So how many batteries would I need
How do you figure this out for a new build?
Theres a good article here that can help you get a rough estimate: www.energysage.com/solar/solar-101/how-many-solar-panels-do-i-need/?rc=p-tophomeowner
@@TopHomeowner Thank you kindly sir. I'll check it out.
@@TopHomeowner Thorough article but it didn't help with new builds where the annual energy usage is not available. I guess I would need to get some type of energy modeling done to estimate what energy usage looks like to determine what is needed.
very informative
Well said
Good info.
Thanks!
Nice vid!
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I watched this video over 4 times, I should like it 4 times.
Unlike like, Unlike like, Unlike like, Unlike like
easy
Why do you have clickbait ads?
That's just youtube...
Barely got through the first minute....before a common mistake was made: power is in units of Watts, while kWh is energy (not power). Power x time = Energy. Minor and common mistake, but should correct it moving forward.