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Home » Basic/Important Electrical Formulas » A Complete Guide about Solar Panel Installation. Step by Step Procedure with Calculation and Images

A Complete Guide about Solar Panel Installation. Step by Step Procedure with Calculation and Images

Solar Panel Installation: Step by Step Procedure

A-Complete-Note-on-Solar-Panel-Installation.-Calculation-about-No-of-Solar-Panels-batteries-Rating-Backup-time-InverterUPS-Rating-Load-and-required-WattsA Complete Guide about Solar Panel Installation

A Complete Note on Solar Panel Installation. Calculation about No of Solar Panels, batteries Rating / Backup time, Inverter/UPS Rating, Load and required Watts. with Circuit Diagrams.

If you pick this post related to solar panel installation, You will be able to;
→ To calculate the no of solar panel (with rating)

→ To calculate the rating of Solar panel
→ To calculate the rating of batteries for Solar panel system
→ To calculate the back up time of batteries

To calculate the charging current for batteries
→ To Calculate Charging time for batteries
→ UPS Rating for load requirement and much more…
Before starting, We recommend to read this Article about Solar panel installation and Photovoltaic Pane Selection for home.
 Now lets begin,
Load = 800 Watts
Inverters Rating =?
Required Backup time for batteries = 3 Hours
Required No of Solar Panel =?
No of batteries =?
Inverter should be greater 25% than the total Load
800 x (25/100) = 200
800+200 = 1000 Watts
This is the rating of the UPS (Inverter)
Now the required Back up Time in Hours = 3 Hours
Suppose we are going to install 100Ah, 12 V batteries,
12V x 100Ah = 1200 Wh
Now for One Battery (i.e. the Backup time of one battery)
1200 Wh / 800 W = 1.5 Hours
But our required Backup time is 3 Hours.
Therefore, 3/1.5 = 2→ i.e. we will now connect two (2) batteries each of 100Ah, 12V.
If the number of batteries given, and you want to know the Backup Time for these given batteries, then Use this formula.
 1200 Wh x 2 Batteries = 2400 Wh
 2400 Wh / 800 W = 3 hours.
So this is a 12 V inverter system, Now we will install two (2) batteries (each of 12V, 100 Ah) in Parallel.

Why Batteries in Parallel, not in Series?

Because this is a 12Vinverter System, so if we connect these batteries in parallel, then the Voltage of batteries (12 V) remains same, while it’s Ah (Ampere Hour) rating will be increase
(Remember: In parallel Connection, Voltage will be same in each wire or section, while current will be different i.e current is additive e.g. I1+I2+I3…+In = 100Ah +100Ah = 200Ah
In Series Circuits, Current is same in each wire or section while voltage is different i.e. Voltage is additive e.g.V1+V2+V3….Vn..
For The above system if we connect these batteries in series instead of parallel, then
The rating of batteries become V1+V2 = 24V while the current rating would be same i.e.100Ah.
We will now connect 2 batteries in parallel (each of 100Ah, 12V)
Therefore for 2 Batteries,
200 Ah 12V,
Now Required Charging Current for these two batteries.
 (Charging current should be 1/10 of batteries Ah)
200Ah x (1/10) = 20A
Now the required No of Solar Panels
P = VI
P = 12V x 20 A
P = 240Watts
This is our required watts for solar panel (only for battery charging, and then battery will supply power to the load)
240W/60W = 4 Solar panels
Therefore, we will connect 4 Solar Panels (each of 60W,12V,5A) in parallel.
Circuit Diagram for the above Calculation for Solar Panel Installation

Click image to enlarge

Solar Panel Installation
This was only for battery Charging (and then battery will supply power to the desired Load) i.e. for those electrical appliances, which will get power through inverter (from charged batteries)
Now suppose there is some (Directly connected to the panels through inverters (without battery) load about 10A, which we have connect directly to the solar panel (No batteries required)
In this case, required current (20 A for Batteries Charging and 10 A for direct connected load through Inverters during sunshine only but batteries will be also charging while panel supply power to the direct connected load.  
In this case, total current,
20A + 10 A = 30A
Now I = 30 A, then required Power
P = V x I = 12V x 30A = 360Watts
(This is for both Direct Load and Batteries Charging)
360/60W = 6
Therefore, we will Connect 6 No of Solar panels (each of 60W, 12V,5A)
And We use Charge Controller about ampere rating i.e, the charging current for 200Ah battery is 20-22 Amperes (22A (For Battery Charging)+10A(for direct DC Load)…So we can use a charge controller about 30-32 Amp.
 Note: this calculation is base on ideal case, so it is recommended to always choose a Panel some bigger then we need. Because when Solar Panel charges the battery so it is wasting some power on charging too.
this is another Circuit Diagram for the above Calculation for Solar Panel Installation
Click image to enlarge
calculate the no of solar panel, rating of Solar panel & batteries , Charging time & current for Solar Panel Installation with image and calculations.

By: Engr Wasim Khan
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  1. Boss you are doing great job. I am proud of you, we belong to same country.

  2. This is a very informative article. Thank you for taking time to share your knowledge.

    • Thanks for Your Appreciation

    • I have a doubt, i.e., i connected 4 no's 12V 145Wp solar panels in parallel (4x8A) approximately with 150AH battery 850VA inverter. As per the above calculations my connection is wrong. How could i correct it.

      • this calculation is not used Practical solar system design and solar system ckt. so plz dont use these formula’s.if the batteries is 150Ah the formula is=load*backup time/750=no of batteries.

  3. if 220 or 380 v power supply , wats the calculations <br />

    • No matter. because this calculation is based on Current for Load. so if 380 instead of 220, then current will be slightly decreased .<br />Because if you increase Voltage, then current decreases ( → P = VI )<br />So Keep in Mind Load only.

  4. Dear Sir,<br /><br />Thank you very much for these information. But I think you didn&#39;t take in your consideration the change in the the temperature or the irradiation which will affect the output solar power.<br /><br />Regards,<br />Mostafa<br />

  5. Dear Sir,<br /><br /> The Info which you are sharing helps me alot, thanx 4r sharing such valuable information. I completed my in the stream of Electrical. I&#39;m very much interested in knowing the calculations of the Load. I have some doubts regarding the selection of ratings of the battery and the connection of battery. <br />1.Here you have taken 100Ah 12V batteries as reference, is

    • Dear N. Abdul Gayaz@<br />Thanks for your positive feedback…Also I did not mind but I am too happy to see that you have interested to learn about these calculations.<br />here (in our blog) You have right to ask many more question about desired topic and I will satisfy you as soon as possible (really..It’s make me too happy to help you). Because I am here only and only for you people.<br />Here

    • Thanks alot for information sir 🙂 🙂 <br />further if any doubts arise i will ask you sir. Hope you will clarify them too. <br />Thanking You, Sir.

  6. dear sir i need some help plz guide me<br />sir we want to run 375W AC submersible pump with solar energy.if we want to run this pump without batteries means online system then how many solar panels( means watt) will be required… charge controller rating… 24V inverter is designed and we have 85W solar panel <br />( 18-20V and 3.5-3.8A)at output during testing… am waiting<br />

  7. Dear sir,<br /> I want ask you with the reference of (complete note solar penal installation etc, sir i have understand the complete installation process accept one thing, and that is 200 AH* (1/10( = 20 A as you quoted in your note, sir the thing i want to know that is the 20A current for charging the batteries, how much time it will get to charge the batteries per houre?

  8. the &quot;10 A for direct connected load through Inverters&quot; case is not shown in the diagram. can you redraw and 2 additional panels so that we can understand how to connect them.

  9. hi i have a 650 watt inverter with 2 solar panel with 320 watt total and connected to a 400 AH battery bank (liquid aced type) but have an increasing in temperature for one battery. i check the connection and my charge controller it is OK.<br />notes the charge controller amp max. 20A<br />how can i solve the temperature problem

  10. not mentioned about charger controller.plse provide simple schematic diagram of the said.<br /> jayarajankb

  11. hi engr.<br />I think you should revisit your controller rating,remember you are handling 30A. Check the power factor of your inverter,it has great effect on your load and back up time<br />Thanks for your effort<br />Engr. Raymond

  12. for a home solar electrification, they consumed of 16 amp of electricity per day.please give me a solar system and its calculations.

  13. Hi there, thnx for the useful information<br /><br />I have installed 2 solar panels, 150 watt each long with 2 batteries 12 V 140 AH.<br /><br />My load is 2 ceiling fans and 2 energy savers,<br /><br />I want my batteries to be fully charged by SOLAR in 11 hrs of time (from 7am to 6Pm)<br /><br />Why my batteries are not being charged fully in a day?<br /><br />Thanks in advance

  14. Sir, <br /> How to deal with Three phase loads while selecting solar panels , inverters , charge controllers , batteries etc ???<br /><br />Secondly, if we have some three phase loads and some single phase loads in room than how we will select system ??? <br /><br />Waiting for reply.

  15. Recenlty i took 800va hybrid digital inverter with 2*100 tubular batteries and 3*100 watt poly panels .my inverter has solar/grid change over switch and technician says it always to be in grid mode and mains grid switch on,but of articles saying morning time we can switch off main power supply and night time on .He says if it is in solar mode and mains switch on it did`t draw power from grid <br

  16. Im doing like that.But at what temperature/lux panels generate current<br />if we charge the batteries at night time how much current consumed ?my inverter show some times 8 amps and 1amp &amp; 4 amps respectively why its not constant

    • Your inverter shows the load current, it varies with changing the load. i.e, if your load is to low, then current will be also low and vice virsa. <br />for more detail…<br />Read these two posts…and you will be able to get the main idea….<br />(1)<br />Easy Charging Time and Charging Current Formula for Batteries. ( with Example of 120Ah Battery).<br />

  17. I want to run 5hp 3 phase motor with solar panel can you please get me the information for this?like what is the panel rating?batteries rating?inverter type(power inverter or normal type inverter)<br /><br />let me know if any additional requirements <br /> Thank you in advance

    • Well friend but it will be very expensive installation!Start current for a such motor is about 80A……during 6 sec if start with load!Imagine what inverter size and how many panels will be necessary……I advice you take a cable from the grid!!

      • [* WordPress Simple Firewall plugin marked this comment as “trash” because: Failed GASP Bot Filter Test (comment token failure). *]
        [* WordPress Simple Firewall plugin marked this comment as “trash” because: Failed GASP Bot Filter Test (comment token failure). *]
        Dear Waseem: I also wanted to connect a room cooler which contains an AC motor with a solar system. I agree that the starting / inrush current is too high so can you suggest a circuit which draws starting current from the grid and when the motor is running and current is normalized then it switches to solar system/batteries?

        your help will be much appreciated.

  18. Do i need MPPT controller for my 800 va solar hybrid inverter, if not for how much va systems it is used ?<br /><br />i have old T 12 tube lights of 40 w(electro magnetic choke and starter) in my home ,when checking the load of them they shows different (90w &amp; 69 &amp;73) respectively (inverter with digital display im checking each individul light).But according to information tubelight

  19. Dear Waseem i have install 100*4=400 watts solar panel in a serial and connect with them 2 battries of 100*2=200 amp. how long batteries becom full and how long its give me backup time if i use 2 celling fans and 1 tv of 14 inch. thankx

  20. This comment has been removed by the author.

  21. Hello Bro<br /> Can we connect the Solar Power directly to an inverter without batteries through a charge controller ?? Is it possible to use the solar power in day time without batteries ?? Hope that you can help me.

    • Dear Padma Priya@<br />Yes! You can… As its not good that first we store energy in the batteries and then convert it to AC during Daytime… in other words, Connect solar panel to inverter and then connect to Load. [During Sun-shine i.e, day-time]

  22. Will battery charge if we connect battery directly with solar panel without chage control device?

    • Yes! As we know that Solar Panel provide DC, also Battery Charges on DC. So you Can… But Do not ignore Safety.. as Charge controller control [regulate] charge for battery.. otherwise, the battery life will be reduce.

  23. Dear sir,<br />I have installed 2 panal of 150 w with two btys 12v 100 ah each in parallel through ups of 1000 va/ 600 w rating. total load is about 02 kw w/o fridge,freezer,tv and microwave oven but at one time we use only300-400 w.<br />Problem faced are<br />1 System starts after 01 hr of sun rise and btys reaches to about 10.8-9 v by evening ,still 01 more to sun set.<br />2 One bty is

  24. sir i want a design calculations procedure for boost dc to ac converter.this converter i ve to connect it with solar panel.<br />In my boost dc-ac converter have four switches wit two inductor and capacitor.i ve to design the value for L and kindly sent me a design procedure for this converter<br />

  25. 100Ah x 24=2400 Wh (when batteries in series and 200Ah x 12= 2400Wh (when batteries in parallel)<br /><br />Than where is the difference ? Wh are same kindly let me know which connection is superior and why?

    • Here is the difference<br />In case of series connection of batteries, we have used 100Ah batteriy but the rating of voltage of the battery is 24V. <br />But,<br />In case of parallel connection of battery, We used 200Ah Battery but the voltage rating of this battery is 12V.<br />So there is a very big difference between 100Ah and 200Ah batteries. <br />And also it depend on you that what system

  26. Asslam.o.Alykum<br />Dear Wasim ,<br />Very Good Work.To much easy way to learn about solar and love this site.<br />Here I want to ask a question that in above calculation why you multiply 200Ah with 1/10 (charging time should be 1/10 of batteries) kindly clear this concept to me I shall be very thankful to you.<br />Regards <br />M.Kashif

    • Dear@<br />It is 200Ah, not 200A…. So first of all we would find its amperes rating. studies and practical have shown that the safe limit is 10% of battery Ah rating for battery charging current. i.e, 20A amps for charging of 200Ah.

  27. Nice work your have done with the explanation above, but I have one question. I was going to buy a 130watts solar panel to be use for charging a 12V 100Ah battery, But when I turned to the back of the solar panel to check for the specification plate this is what was written : Solar Model type— SPM 130 -12, Peak power (Pm)—-130W, Maximum power voltage.

  28. Nice work with the explanation above, but I have a question. I was going to buy one 130watts solar panel to be used to charging a 12V 100Ah deep cycle battery, but when I turned to the back of the solar panel to check for specification plate, these are the information I saw: Solar Model type— SPM 130-12, Peak power (Pm)—- 130W, Maximum power voltage (Vm) —-17.2V, Maximum power current (Im

    • A 12V Solar panel gives about 22V(Open Circuit)<br />In simple words;<br />Panel Wattage = 130W<br />Volts = 12V<br />So current would be <br />I = P/V → 130 / 12 = 10.83A (Ideal Case)<br />So you can use it for 12V 100Ah battery<br />and charging current for 100 Ah battery = 100Ah x (10/100) = 10A<br />and the charging time for this battery would be;<br />100Ah / 10 A = 10 Hrs (Ideal)<br />

  29. Warner Carter

    The Department of Energy’s Lawrence Berkeley National Laboratory produces an annual Tracking the Sun report (pdf file) into the prices of photovoltaic (PV) power systems.

  30. Respected sir,<br />tell me how we choose invertor voltage size 12, 24, 48 or 96 ?<br /><br />Zubair

  31. Sir,<br />Is it okay to connect three batteries in parallel,150ah 100ah 100ah

      • dear sir i have two solar panels of 30 w each and also 28 AH Gel batteries i have already connected them in parallel and using them as 12 v DC system but i also want to charge them on wapda in the absence of sunlight so that i can use it as a hybrid dc system
        please guide me the auto transfer switch diagram which should be in relay logic control or ready made controller model no

    • Dipak Chowdhury

      But charging current is different for 150Ah & 100Ah, 15A and 10A respectively. Charging time will be different for both the batteries.

  32. Sir, do we have any Calculator for:<br />Calculation on No. of Solar Panels, Batteries rating/Backup time, Inverters/UPS rating, Load and required Watts. If so, please share the url or CalC on my mail ID ( <br />Thanks in advance..

  33. sir thanks for the knowledge above..<br />but i want to know more related to transparent solar panel.<br />i wnt to study more on this research topic, from where should i be able to get??

  34. Hi all, I have a project to specify solar panel equiptment required to power a 4200 watts refregirator over a 12 hours period. I calculated the equipment wattage over 12 hours to be (50,400 watts at 4200 watts per hour). A total of 168 solar panel unit (at 300watts solar panel unit) would be required to generate this type of output at once. Also a 24volts 200amp/hour battery will give me

    • In your case, The Power consumption and back up time of batteries it too much high..therefore, Solar panel system would be too expensive.. So i recommend you to do the same with power cable from power grid instead of solar system..

  35. Thank you very much sir<br />

  36. noshin mmuqadas

    sir i am working on a project.i have load of 100W .i have to design a solar panel.please guide me how to do design calculations of numbers of batteries,panels,inverters,panel factor etc.please send the data on my id<br />thanks <br />noshin muqadas

  37. Hi,<br /><br />Please tell me the calculation for solar panel to charge 12V 100AH SMF batteries which are connected in series to get 96V.<br /><br />Thanks in Advance.

    • How many batteries? and batteries with direct connected load or without direct load?????

    • Dear Sir,<br /><br />I have connected 8 batteries of 12V 100AH SMF batteries through Emerson 2KV Online UPS.<br />Due to load shedding batteries will not get charege on AC power supply.<br />Hence i m trying for Solar option to charge batteries.<br /><br />Thanks

    • Dear AB,<br />if you want to charge only batteries through solar panel. then the total wattage of batteries bank = (12V x 100Ah) x 6 batteries = 7200WH <br />and the charging current for these 6 batteries = (100Ah x 6) / 10 = 60A. <br />Now = 12V x 60A = 720W (This is the required wattage for batteries charge only)<br />Now the required no of solar panel<br />720 / 180 =4<br />So you need to

    • Sir,<br /><br />I think you are considering 6 batteries of 12V 100AH which are connected in parallel, but my UPS support 96V so i have to connect 8 batteries of 12V 100 AH in series.<br />According to that my charging current for these 8 batteries = 100/10 = 10A.<br />Wattage for batteries charge = 96V x 10A = 960W (as per my calculation with reference to your post)<br />Now solar panel

    • Absolutely right..<br />Use Charge controller about 10-12A<br />

  38. Suresh Satapati

    My inverter shows &#39;no feedback&#39; when sunlight night time it is good what is this problem.

  39. thanks

  40. Hello sir, <br />With reference to the above calculation may i know how much sun hours have you kept for calculation. for how much sun hour s the batteries being charged for 800 watts loads?? Thank you

  41. Hello sir, I need some clarifications <br />With regards to your above calculation you have stated that for a load of 800watts it requires two 100 ah battery for a backup for 3 hours. will that 200ah battery satisfy the load of 800w for 3 hours practically???<br /><br />Refering to the formula: <br /><br />Battery capacity = (total load * backup hours) / battery loss * system voltage<br />

  42. There are some losses and efficiency factors playing a major role in output.<br />Battery efficiency : 0.8<br />DOD depth of discharge : 0.8<br /><br />if your using inverter then the factor is : 0.9<br /><br />

  43. Sir,i am working on a project.i have load of 120kWH/mnt . And i want to generate 200kWH/mnt.i have to design a solar panel heat collector and stored it in power bank.please guide me how to do design calculations of numbers of batteries,panels,inverters,panel factor etc.please send the data on my id<br />thanks

  44. sir yeh artical download ho skta hy kaya<br />

  45. Thank you very much for this very informative and useful article! I am very happy to read this, liked!

  46. Hai <br />Very nice discussion. i have started reading this with 0 knowledge on Solar power. now i gained good knowledge. thanks for this work.<br />After the calculation i need around 220 AH battery is required for me. Now I have 100Ah battery and am planning to connect 150 Ah battery in parallel. <br />is it suggestible 100+150 AH= 250AH comibnation…?<br /><br />Thanks <br />Dr. Kumar

  47. HI,<br />I have setup 120watt panel with 30amp charge controller with 7.2ah battery for fun.<br />During Daytime I use it to power my laptop ( using laptop car charger) and draw current directly from panel. But this goes unused most of the days.<br />I am planning to expand this setup as the battery (from my old ups) is of low capacity. I am planning to use 88ah or 100ah (tubular as they all

  48. hello sir thanks for this great knowledge..<br />i want to install 5 kw solar pv then please tell me about the inverter i want to use solar inverter so there will be no use of dc controller (shown in figure) and i want to use 1500Ah 12v battery then please guide me the rating of panel inverter and battery bank (back up 4 hr) ASAP

    • Dear Sir,<br /><br />I have a doubt, how to select the voltage system (i.e, 12V or 24 Volt in DC) or 11KV, 22KV, 33KV voltage in AC for required power in electrical system<br />

  49. i have at random got installed solar with 10 panels of monochrome 150 wt and 3 kv hybrid NS and 12 v 90ah 4 batteries arranged for 24 v. these can run two ceiling fans for 5 hours, is it ok as i am feeling it unsatisfactory?

  50. Hi<br />My name is Abraham Oni from Nigeria ,West Africa.<br />I can not but write to appreciate this great information made available to all at no cost. I thoughgt it wont cost me anything to say thank you for clearing my doubts about some issues well discussed here. They are really helpful.<br />I will love to learn more from you sir and if possible and if you dont mind becoming my teacher on

  51. Aslam-o-Alikum Sir, Im Kashif Raza from Lahore. Kindly look deeply in my case. I have a UPS of 1000 Watt (as the dealer said) and have attached 2 battries of 175 Ah in series i.e 24 V 175 Ah. I recently bought 2 solar panels of 150 W each and charge controller of 30 Amp. Kindly guide me that how can I make connections? I want both WAPDA and solar charging. I mean at day time battries must be

  52. hi dear I have batteries that have 2 volts and 800 amps total (24 batteries) and my load is 8000watts what solar system will be suitable for me and also what will be the backup of these batteries ? <br />thanx in advance waiting for your help<br />( )

  53. one more question can we use a car alternator of 24volts and 150amp instead of a solar panel?<br />yes I know you question how to run that alternator?<br />the answer is with a 2hp motor that run on a inverter<br />( I mean motor run on a inverter that has 5000watts capacity and that motor starts the alternator and gives the 27volts and 150amps to inverter ) is this possible plzzzzzz help me in

  54. how can we design a 3kva solar system in 24 volts

  55. dear sir<br /> i want to one question of you.i am from radio station .our 7.5kva online ups and we are use 15 tubler battery 150 amph. we want to use solar how many solar panel required to 6 to 7 hour back up?now our battery back is 3 hours.

  56. An excellent Effort and a great positive approach in sharing the whole methodology for Free.<br /><br />Stay Blessed and well done

  57. Dear sir.<br />I have installed axpert 3kva, 24v mks plus inverter, 2 AGM 150Ah battries in series. 4 solar panel each 230 watt in 2strings, means 2,2 panel in series and then both strings in parallel. At this stage connected load is 750 watt AC at day time and 400 watt at night. <br />Use of 3kva inverter to increase of future load.<br />I jst wana cnfirm that:<br />1. my installation of

  58. sir i have 800va inverter with 12v , 150ah battery. i need to use solar panels. can u tell me how much solar panels watts required for charging the battery and give load. how much amp i should take the solar controller.

  59. Hello Sir, firstly I would like to thank you for your explanation,they are clear and very helpful, I just have some questions: 1. what is the discharge capacity of the batteries that you used in the example?, 2. actually I have a project of using Solar panels for my company(our load is 3580 watts per one hour, so i came out that I will need 33 panels of 300 watts each and 24 batteries (200Ah,12v

  60. Sir Please kindly tell me if I connected two batteries (each of 175Ah) in series , then who i find the chairging
    time of batteries in series (24V) and requried back up time for batteries

  61. Hello Sir, i have solar power generator the main battery is 100ah while the backup or the other battery connected is 150ah, is it okey to have different amperes of battery connected? thanks

  62. Dear Mr. Khan,

    Have a very nice day ahead,

    We are looking for solar inverter, which will most be used on day time, so we kindly request you that ,did you supply us the day time inverter ( without battery ) from 3.5 Kva – 5 Kva

  63. Assalam alaikum

    Can we use 24v solar panel in place of 12v panel for charging 12 v battery.

    if yes can we reduce 50% panel because they 24v. panel.

  64. I have 2 solar panel one is 60w and another is80 w and two battery How to connect this to best working

  65. rosalin pradhan

    Dear Sir,
    In the last part of calculation ,from where u got 60w to get 4 no.s of solar panels?


    • you can use the available panels you have like in the above expression he assumed he has 60w panels. if you have have 100w you substitute the value with the number of panels available. stay blessed.

  66. Thank you verry much sir you are doing great job.

  67. Hello Waseem,

    You are indeed doing a great job here. I was troubled with what number of solar panels to be used for solar installation in my house, I kept searching and finally got your wonderful link, its very-very educative and well explanatory. I really learned a lot from your pull of knowledge.

    Below is my proposed installation, kindly check if am correct with all these specification and advise accordingly.

    3.5KVA Inverter is to be used, 4#s of 12V/200AH Battery, Overall appliances consumption=1000 Watts (Points of light, TV set, Home Theater, Deep Freezer, One 1.5HP Air Conditioner and Two Ceiling Fans), Needed backup time=(8-10)Hrs.

    My Calculation: Battery Rating – 1000W+(25% of 1000W)=1250W=1.25KW.
    200AH x 12V = 2400WH. Therefore, for 4 Batteries; = 2400 x 4=9600W.
    To determine the number of solar panel needed: 1/10 of 4# of 200AH battery = 1/10 x 800=80W,
    Hence: 80W x 12V x 1.25 (power factor) = 1200W. Hence, a 1600Watts panel is assumed to be used, each of 200W, making 8#s of 200Watts Solar Panel.
    Will this work as expected at-all? Is the calculation correct? In-case I used 2#s of 12V/200AH Battery, will this work, I understand that the backup time would be reduced to (4-5)Hrs.

    • Hakeem, I dont think this is going to work as I am pretty sure that the initial current of your airconditioner/Deep freezer is going to drain your batteries instantaneously. The discharge current of the batter should be about 1/20 of the total Ah rating if you want the batter to give constant voltage over a long time. this means a 100 Ah battery should be loaded with 5-8 Ampere current if you want the battery to operate as expected (exact figures can be seen from the data sheet of the particular battery).

      Appliances like Fridge and ACs have a very large initial current requirement then it settles to a low current later so you will have to keep the in-rush current in mind as it will require you to have too many extra batteries just to support the initial current. Maybe Waseem has a solution for this, I would like to know.

  68. Dear Sir,
    I have 2 nos of 12 volt 120 amp battery and 800 watt 24 volt APC Invertor. What shold be the size (wh) of P V pannel. Kindly suggest me

  69. I envy your piece of work, appreciate it for all the good blog posts.

  70. Dear Sir,

    This is very useful and simple method for understanding the Solar system design.

    I have one query hope you will guide me on that.

    How you have calculated the current as 10 A for the direct load to be catered from Solar inverter.

    I will be happy to hear from your at the earliest.

    Thanks & Regards


  71. lukesacristan

    thank you sir for your very nice link.. i learn a lot….. regarding the connection of solar system….before i have no
    idea for that,,, GOD BLESS US..

  72. Hello ,

    First of all i would like to appreciate you for sharing this information.
    Secondally i want ask for some help . I have a ups 600va with a battery of 12v 7ah, i want to charge it with solar panel.

    I will be using this system as backup, led light,rare cases to run desktop. I need to have least possible configuration cost wise.
    I have selected 10-20 watt panel and want to know can i use 12v 6 ampere charge controller?.

    Also is there any more information for selecting charge controller?.


  73. Salaam alaikum. Sir, from the last point on finding the current for both charging and direct connected load, starting from where it reads “Now supposed there is some (directly connected to the panels through “inverters”)”. Is it inverters or charge controller?

  74. dear engineer, i have one doubt??? i have designed the inverter. but how to find out the rating of the inverter. up to which load it can handle??? how to find out??

  75. Very Good post sir after reading this i am now able to set up solar panel to my house 🙂

  76. What is the specification for 1kW off grid and 1KW on grid ? ( want to know solar panel in W, battery need to be used, charge controller and inverter VA)

    thank you

  77. sir i m making sun tracking solar penel can u plz tell me how much watt of stepper motor i used?


    Sir, I am a Civil Engineer . I have got solar sytem for 3Kw system . Solar Contractor installed 6 panels( Series of 3 Panels connected in Parrallel ) , each rating 200 watts connected with 8 batries of 100 Ah( connected 4 batteries in series to make 48 Volt Circuit ) with charge controller & Inverter . My First question is it OK combination from point of view whether this system is sufficient to charge the batteries ? Second question is what will be the Back up time If I am putting regular 400 watts load during day time .I do not have any knowledge for electrical engineering for solar products at all . Kindly help me since your above calculations are not matching with my installed system or I could not match my system with your guidelines . Also let me know if 200 watt panel will produce this much wattage per hour or per day , regards , Er Hari Singh Matharu

  79. Thank You very much for sharing the article. The installation is really a great task, but have clearly explained the methodologies.Really Informative. It’s not so tough compared to the hybrid generator installation, I can share with you the methodologies for Hybrid generator installations.

  80. I would like to know why inverter rating is 25% more than the Load.

    Also want to know we have install 7.5 Kw plant in which we used 300wp of 25 Pannels and 7.5 KW inverter.

    But we are getting only 5.2 kw generation at the mid day time in the mid month of May.

    • Hello Raj…
      The rating of Inverter should be 25% more than the load because of the output efficiency of the inverter and losses (As, UPS never provide 100% output).

      300W x 25 = 7.5kW…and you get 5.2kW…. there are lots of factors… i.e. sunlight, PV installation position, Quality of the Panel, losses, cable quality etc….

      You may get support & help from the retailer as well as manufacturer then…

  81. kan singh bundela

    i have 20 nos. 24 volt/250 watts solar panel , 360 volt/20 kw inverter & 30 nos. 65ah Battery. please tell me how connect of solar panel in 20 kw inverter and what rating of required solar charge controller for solar charging.

  82. Sir kindly explain about battery in Ampere required for 80 watt solar panel?

    • Ashwamedh Solar Equipment

      Presuming your 80 watt panel is of 12 volts would generate 4.7 A current hence you would need 12 V / 60 Ah @ C-10 rated battery.


      Your 80 watt panel would generate 4.7 A current hence you would require 12 V /60 Ah @ C- 10 rated battery.

  83. Sir I want to use solar panel 450 watts for 420 ah battery.
    But I’m confused how much solar panel use for better charging.


      Dear arman,
      Presuming you have all panels in 24 volts, you can make a 24 volt battery bank and connecting the panels in parallel through a 24 volt 30 amp solar charge controller.

  84. Hi
    My application is for purely digital appliances. Router, Switch, Access Points.
    Load is 200 Watt
    I would like to use solar panel for 8 hours.
    I want to use DC directly for my load.
    However other time (16 hours) I want to use normal 230 volt-raw power. pl advice. Can it be automatic switchover?


      Hi Rahul, your requirement is unique.It is possible to make such auto switching equipment if yoy are ready to bear the cost.

  85. Sir, I intend to attain at least 1kwa load powered by 4 12v 250 watt solar panels, four 12v 200Ah batteries; how do i connect my panels to achieve a maximum charge? how long can my backup last at peak load. Thanks in anticipation.



      Since you have 12 V panels each one would generate 14.61 A current hence you should connect the panels 2 each in series – parallel combination. Similarly in battery bank also to make it a 24 V system.This would give you at least 4 hrs. back up with 2 hrs autonomy.

  86. Really Thankful

    this is really super helpful!!!!! thanks!!!!!

  87. I just want to know how much time and current required at a time to charge 10 no of 150Ah batteries by solar power plant. Or
    if we use 6 250W/24V Solar panels in series to match 144V PCU intput requirment and prepare 3 line for same for 5KW solar power plant then how much time this system will take to charge 10 no of 150Ah batteries?? Please suggest how to go forward.


    As stated by you, you have 10 batteries of 150 Ah and 6 modules of 24 V / 250 Wp. These you can use in two different ways considering the operating voltage of the PCU.
    1. Make the system in 120 Volts by adding all the 10 batteries in series and connecting 5 of the above modules in series to make system in 120 volts.

    2. Make the system in 144 volts by attaching 12 batteries in series and all the 6 modules in series.

    In both the cases the full charging period will be about 16 hrs. as you have only 7.14 A current available from each of the module.[Pl check the label on the back side ]

  89. Thanks for your valuable suggestion. Can you please share your contact details if possible?

  90. Hi
    Thanks for the great post. Read it in one shot.
    Really motivated to go Solar.
    Already have a 1KW Inverter with a 150AH battery in house.
    Approximate load is 350-400W concurrent usage
    Was thinking of how to achieve the desired model
    Run Morning to evening daily home load(~350-400W) directly through solar
    Also in parallel charge the 150AH battery for backup purposes in evening.
    If possible add one more 150AH battery and charge that as well for additional backup
    Whole idea is to reduce dependency on the grid

    Please advice how many watts of SOlar panel are required for above
    What spec of Solar charge controller is required
    Also is it possible to charge battery and parallely run the laod directly during day time from the solar charge controller

    Many thanks in advance


    Since you have not mentioned specifically,we presume that the battery you are using is a C-10 rated battery and the inverter is 12V / 1kVA inverter [ 800 Watts ].
    1. Under the present set up if you want to employ the existing battery only,then you can connect 2 solar modules of 12V /150 Wp each in parallel to charge the battery In case if you want to have more back up you can include another similar rated battery in parallel to the existing one and connecting totally 4 solar modules of 150 Wp in parallel that will charge the total battery bank.

    For this purpose you would require 12V / 40A Hybrid solar charge controller which would run your inverter online and charge the batteries at the same time.

    • Many thanks for the reply.
      I had requested a quote from a dealer for this setup and he is claiming he can put 600W panel that can concurrently run the 350W load along with charging the 150AH battery. Based on your reply i think its just a claim and wont work . Another thing i want to know is can a solar hybrid charge controller run the load as well as charge battery for all inverters. Reason i ask is, the dealer has claimed today that running load directly from charge controller and charging battery works only with brands liek APC and not other inverters.
      just want to understand how a solar hybrid charge controller works and its dependency on the brand of inverters.


        A hybrid charge controller can convert any inverter of any brand into an online solar inverter and it has nothing to do with the brand name.


    My brother thank a lot for your help .i have some problems which i need the solution
    i have 12 panel i want it to connected in parallel [12v.DC] SO HOW MANY BATTERIES ARE NEEDED


      You have not mentioned in your message as to of what wattage your solar panels are of. If each panel is of the same rating please inform accordingly.Then only we will be able to advise you in this regards.


    In fact a hybrid solar charge controller converts any inverter of any brand into an online solar inverter.It has nothing to do with its brand.

  94. Dear Sir,

    could you please let me know which kind connection ( Parallel or Series) of solar panel and Batteries are good to be follow, for example we have two solar panel 250W and tow 100 Ah Batteries.

    Best Regards,



    Mr Ahmed,
    1. Since you have both panels of 250 Watts, they are in 24 volts rating [ see label on the back side of the panel ] hence you must connect them in parallel.
    2. Since you have 2 batteries of 100 Ah rating you must connect them in series.

    This will make your system a 24 V system and for this you will require a 24 V solar charge controller.

  96. Sir,
    I recently installed 24V({2X12}X2)-4 battery 150AH each) solar system. My battery connected in parallel. But 4-solar panels connected in series. charging voltage fluctuates 60 to 75V in 3 seconds and current varies from 13 to 18.8 in peak hours. As per my knowledge y solar panel also should be connected in parallel as per the manual supplied. They are telling it it is new technology(MPPT) ,so it is connected in that way. As per my knowledge A C10 battery (150AH) minimum charging current is 15A ,, in the manual panel it is fluctuating from 10 to 13A and on the inverter screen it is from 14 to 18.6 in peak time. for a day average charging current is 8A. I am getting 3 units per day as per their manual and solar around 4 units. My fear is that the panel connection is wrong and because of law current my battery may be driven into sulphation. Any idea where I am wrong?

  97. Sir, I am a Civil Engineer . I have got solar sytem for 3Kw system . Solar Contractor installed 6 panels( Series of 3 Panels connected in Parrallel ) , each rating 200 watts connected with 8 batries of 100 Ah( connected 4 batteries in series to make 48 Volt Circuit ) with charge controller & Inverter . My First question is it OK combination from point of view whether this system is sufficient to charge the batteries ? Second question is what will be the Back up time If I am putting regular 400 watts load during day time .I do not have any knowledge for electrical engineering for solar products at all . Kindly help me since your above calculations are not matching with my installed system or I could not match my system with your


      Mr Mukesh Kumar,

      Since you have not mentioned in your message ,whether your solar panels are of 12 / 24 volts rating. However since all your panels are of 200 Watts they must be in 24 VDC rating..[see the label on the back side of the panel].

      Accordingly since the battery bank is of 48 VDC the solar panels should be connected in 2 – series X 3 – parallel [total – 6] combination.Making it a 48 VDC system.Please check at your end.

      This system should be generating a minimum current of 17 Amps, @ 48 VDC. Considering your batteries are of C- 10 Rating, the current required is 20 Amps. However the existing system should generate about 3264 watt hrs of electricity in 5 hrs, on a normal sunny day.

      If you put a day time load of 400 watts , it would give you a total back up of 7 – 8 Hrs per day.

  98. I have a solar panel of 48 V and 3KW inverter supported by a 48V 150AH battery bank of 08 nos. I would like to know how much load i can utilise from this set up and can i use aircondtioner 1.5 ton 4 hrs and pressure pump of 1hp 1 hr that is used with my other general appliances and not ties to the grid.Please assist if i need to correct this arrangement

  99. Doulathrao Kadam

    How Much solar panel requried for solar inverter 1660VA of operating Voltage 24. The load on this inverter is in day time 420W

  100. Sir
    I a have 24 V solar system 4 battery ,150 Ah battery connected in parallel(2X12V+2X12V) installed two months back. What is the current/Voltage, supplied to the battery for charging. Now maximum is 29A. Which means 1 bank(2X12V Battery), it is below 15A. For a 150AH battery I read the minimum current required for charging is 15 A. I used to get 4KW from sun. and if I am not using the system in day time , the battery is providing only 2.2KW(automatically trips). I came to know that if the inverter factor 0.8 then the battery should provide 3.2KW. Please help me.

  101. Sir, i got 1646wh of loads, what if i use 4batt (12v 40ah) , (4panel 100w, imp 5.62, isc 6.07, vmp 17.8) , chargecontroller rating 30amp, and cable size 1.5mm for 27amp. Do you think my system will work? Ive follow your calculation based on loads consumption, just my battery backup time is 1hour. My location best tilt angle is 10* facing south,

  102. I have 2.4kva/24v inverter and four 200amh batteries. How many solar panels of 300watts

  103. Quick question. With 250W Solar panel 24v and two batteries of 12v,which will be the best configuration of batteries, series or parallel? The question come because I have 12v bulb and 12v inventor.

    Thank you



  105. Engr Muhammad Abdurrehman

    Superb work MashAllah, Carry on like this our best wishes and prayers are with you sir!

  106. I want to build myself solar fencing. It should give 2000v dc supply shock for animal.fence will have 5 lines of 12 gauge gi wire.hope the animal will not die.

    For this I was under impression I need one battery,one charge controller,one solar panel,one invertor and one energiser(I do not know what is energiser) and 12gu gi wire. These are main thins in addition to poles,insulators,etc.
    Please let me know what should be specification of battery,charge controller,invertor,energiser,and solar panel,
    So that I can buy these and go ahead.
    My assumption is invertor is needed only for lighting needs.

  107. We installed 280 watt panel ( 2 panel Each panel 140 watt ), 30 AMP charging controller, 200 ah battery and 800 watt inverter

    My question it is wright or wrong ?

  108. We installed 280 watt panel ( 2 panel Each panel 140 watt ), 30 AMP charging controller, 200 ah battery and 800 watt inverter

    Also we using Dc light ( 5 watt 10 light =50 watt )

    My question it is wright or wrong ?

  109. Dama patrick Iga

    i need a technical proposal for three phase 30KVA back-up system for off grid plant ,
    how can come up with the sizing of the system

  110. i really appreciate u for sharing the information in most simple manner,its possible for any laymen with basic knowledge to understand the solar system calculation.Great

  111. i want to purchase 100w x 3 nos solar panel please tell me/ about the power of solar inverter and batteres

  112. I really found ur article very informative. I have one question;
    What is ratio/ equation between power of PV panel & Amp of its controlling device?
    I.e as different power of panel controls by different controlling devices.

  113. Hello engr.please i need advice on the comb if is right to go not good in scientific language.
    Inverter of 2.4kva
    Battery of 200ahms(only one)
    Solar panel of 250watts (only one)
    Charger controller 30am…
    To control basic things at home eg one fan,3led bulbs,tv led only.
    Should i go ahead with the combination?
    Pls advice and recommendation will be needed sir.Thank you in advance

  114. hi how are you doing this augustine …..which controller can i use for 5kva/96v using 8battery 18panels—200watts

  115. Altaf hussain

    Dear Sir
    I wants to installed 3000 watt solar system in a home. pleae guide me for design
    out put voltage = 220v, 50HZ

  116. Nice work sir g . I need some guidence from you that i wanted to install 10 hp sumersible pump what should be the rating of inverter and according to my calculation it should be 2000w inverter if iam wrong please correct me

  117. Please i need your help..I already have on ground 3.5kva 24 v inverter and (2) 180ah 12v battery. Would like to go on solar panels.. how many panels will i use ..Thanks

  118. Please help. I have a 6 KW Devel sinewave inverter With a 60 amp MPPT E Tracer Controller on a 48 volt system and 8 x 300 watt ecco 24 volt panels coupled in series to give me 48 volts. Now i want to know how many 300 watt panels maximum can i couple to this system to give me more day power from the panels without damaging the controller. I have at the moment only 8x 77ah Batteries on 48 volt coupled but intend to improve as my money allows me to. I am only running lights at night now. My only concern is not to overload the MPPT controller at this stage. What can my maximum 300 watt Panels be?

  119. why is not using battery of 24v ins teat of 12v in order to increase watt?

  120. Smart The Best one

  121. how can I arrange the 8 batteries each of 100Ah/12v to give the output of 12V, 24V 48V,96V

  122. We have 4 panels of 250W, 7amp.

    we connected all 4 in parallel.

    But we are getting only 18 Amp. charging current.

    what is the maximum charging current we can draw from 4 solar panels of 250 Watt, 7amp.
    for a 24V solar inverter system. Battery = 2 in series of 12Volt 65Ah

  123. Thanks to inform us about flexible solar panel which I want to connect with my solar freezer to save electricity.

  124. Sir mere pass single battery hai or 250 watt ki solar plate hai or uske upper 2 celling fan ka load hai.fir bhi kuch der fan chlane ke baad inverter whistle bajane lag jata hai.Isliye sir main iska karn puchna chahta hu.

  125. We have 190 watt cooler and want to run 18 hours in a day .for this how many solar pannels and batteries are required??

  126. Muhamad owais

    I have a solar plate of 250 watt .
    And now how can i install it ….

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