In this post I have explained through calculations how to select and interface the solar panel, inverter and charger controller combinations correctly, for acquiring the most optimal results from the set up.
Calculating Solar Panel, Inverter and Battery Charger Specifications
For the sake of convenience, let's believe you possess a a 100 watt appliance or load that you would like to operate, free of charge through solar power, for around ten hours every night.
In order to exactly determine the dimensions of the solar panel, batteries, charge controller and inverter the following mentioned parameters will need to be strictly calculated and configured.
If you do not want to do all the calculations manually, you can simply use the following calculator for getting the results quickly:
Solar Panel, Inverter, Battery Calculator
Solar Panel, Inverter & Battery Calculator
This calculator determines the required solar panel wattage, inverter size, and battery capacity based on your power consumption and backup time.
Results:
| Solar Panel Wattage | Inverter Size | Battery Capacity |
|---|---|---|
| 0 W | 0 W | 0 Ah (12V) |
Estimating Load Wattage
1) First you will need to estimate how much watts of electricity you may require for the specified load.
Let's say you have a 100 watt load that needs to be operated for approximately 10 hours, in that case the total power required could be estimated simply by multiplying the load with hours, as given under
100 Watts x 10 hours = 1,000 Watt hours. This becomes the absolute power necessary from the panel.
Determining Approximate Solar Panel Dimension
2) Next, we need to determine the approximate dimensions of the solar panel for satisfying the above estimated load requirement. If we assume a roughly ten hour daily optimal sunshine, the specifications for the solar panel could be simply and quickly calculated as explained in the following expression:
1,000 Watt hours / 10 hours sunlight = 100 Watt solar panel.
However, you may notice that mostly during the summer seasons you may normally get around 10 hours of reasonable amount of sunshine, but the winter season may produce roughly around 4-5 hours of effective sunshine.
Contemplating the above scenario, you too might agree and recommend considering the worst possible sunshine hour into calculation so that even on the weakest of sunshines your load keeps running optimally.
Therefore taking into account the 4 to 5 hours sunshine per day consideration, we calculate the true power for the solar panel which would enable your load to keep running throughout the year .
1,000 Watt hours / 5 hours sunlight = 200 Watt solar panel.
Calculating Battery Ah
3) Once you have calculated the solar panel as per the above calculations, it's time to calculate the AH rating for the batteries that might be required for operating the specified load under all conditions. If the selected battery is rated at 12V, in that case:
Dividing 1,000 Watt hours by 12 Volts = 83 Amp Hours of reserve battery power.
Let's upgrade this value a little more with a 20% added tolerance, which finally gives a rounded up figure of around 100 AH. Hence, a 100AH 12V battery is what you may finally require for the inverter.
Evaluating Charger Controller Specifications
4) Now, to figure out how big your solar charge controller would need to be for the above calculated parameters, you might need to take your solar panel current or the Amperage specs into consideration, which may be simply gotten by dividing the panel's wattage rating with its voltage rating (Ohms law remember?)
100 / 12 = 8.3 Amps.
We have so far applied a "plus tolerance" to all the previous parameters, so let's show some generosity to the Amp spec of the panel also, and instead of sticking to the 8.3 amps limit, you might be happy raising the level to around 10 Amps? That looks good, right?
Assessing Inverter Specifications
5) Finally we boil down to the inverter specifications, and determine the reasonably exact capacity that would keep the unit compatible with the above discussed results, and keep the load running without issues, whenever required.
Well, calculating the inverter specs doesn't look difficult at this point of the discussion.
Since we already know the maximum load wattage which is 100 Watts, implies that we simply choose an inverter which might be capable of handling a 100 watt comfortably.
That implies, we simply need to get an inverter rated at 100 watts,.... OK, you may be thinking of adding some tolerance to this candidate also, not an issue, instead of 100 watts you can opt for a 125 watt inverter, allowing all the gadgets to happily "shake-hands" and your house powered round the clock forever, free of cost.
Questions & Answers
please get me a practical circuit to make a 2000w inverter to work from 300v dc to 230v output
dear Swagatam
in calculating the actual power delivered by a solar panel do we have to consider the efficiency of that panel so as not to undersized the panels required?
Hi Richard,
Yes, when calculating how much power a solar panel really delivers, we need to consider its efficiency. Efficiency tells us how well the solar panel turns sunlight into electricity. If we ignore this, we might end up with a system that’s too small and can’t provide enough energy to meet our needs.
What does c37 & c38 stand for and what it does in the circuit.
Thank you
Which circuit are you referring to?
very insightful. thanks.
pleas tell me How much the design insulation (ESH)?
Your Discussions are very helpfull
I have 900w,72v DC brushless intelligent self-priming pump, how many panels are needed to run it.
How many solar panels are needed to run a 850w DC BRUSHLESS INTELLIGENT SELF-PRIMING PUMP ON 72V
You will need a 900 watt 72 V solar panel, you can create this by adding many small panels in series and parallel.
Sorry, I do not have it at this moment.
Not 5000 load is 500 load for 12 hours
I have explained the procedures in the above article. Please use the above data to calculate it yourself.
Pls help me to size panel, charge controller, inverter and battery (5000 load, 12 hours night run) God bless you
What is the fault of my inverter displaying zero input and output voltage
I really appreciate the presentation on this site. Very beneficial, precise and informative. Thank you.
Thank you Engr. Abdulhafeezh
After going through the tutorial above, the question i want to ask is how do I calculate or determine the amount of voltage and Ampere to charge 2 units of 200ams battery and 4 units of 300watts solar panel
For a 200 Ah battery, you will require minimum 20 amp current.
I have a total load of 600w to run for 6 hours, what is my calculations to know the batteries, inverter, panels and charge control I should have
Thanks for the good works. Plz can you help on printed circuit?
Sorry, I can’t supply PCBs.
I have a 4kva inverter with 4 batteries if i am charging it with 8 unit of 300watts solar panels how fast can the sun charge the batteries while supplying light after the sun has gone down
Please provide battery voltage and Ah specifications, and how are they connected, in series or parallel?
Thanks
Please, what can i alter to change to the desired solar charge controller(referring to solar charge controller circuit)
You will have to alter the solar panel and the battery to match your solar controller
thank you
Pls what is the best way to connect panels, is it series or parallel when using a 4x 220amps batteries and a 60amps charge controller.
Mind u my panels are in 200watts.
It will depend on the battery voltage and current.
Hello our able instructor,I ‘ll need your attention on transformer less inverter circuit with a clearer analysis sir, since I have little knowledge about the construction remain bless sir and more grease to the elbow
Hello Olufemi, for transformerless inverters you can refer to the following post:
3 Best Transformerless Inverter Circuits
What is the recommended setting on the solar charge ontroller
Morning sir I have two 200watts solar panels and 2000watts inverter and 200ah battery but still can’t have power for 5hrs
Hello Godfrey, a 200 Ah battery will require a charging current of at least 30 amps for first few hours which must be reduced to 20 amps after sometime….A 200 watt panel will not be able to supply such high current, and therefore the battery will remain under charged.
Thank you God will bless your wisdom
Total Home load is 3600W expected to run for 20H daily let us say 30-40%
I have 12pcs 350w 36v solar panels
I also have 4.5kva inverter
I also want to have 6-8pcs 12v 220AH batteries
I want to know the size of charge controller to use since I have 36v from Panels and 12v for batteries and inverter.
For charging 12V 220 Ah batteries, you can use a 12V/30 ampere charger with auto cut off, and install them individually on each battery.
Thank you for the knowledge you are giving.
I want to get something out.
I have
3 TVs 105W=315W( 12hrs)
1 Washing Machine =450w(3hrs)
5 Fans 50W =250w
3 Laptop 80W= 240w(18 hrs)
20LED light 30W= 600w (20hrs)
Cooker = 400w (3hr)
Deep freezer= 300w
2 A.C 1.5hp(1125 W) =2250w(24/7) (12 hrs)
something yet to be added= 95w
The total wattage is 5000w.
Can you please do the breakdown to the barest minimum for me.
1.Would like to know amount of watt estimated per day
2.best inverter voltage to be used and best and Ah calculate
3.Solar panel calculated
4. How many kva is best and volt system and number of batteries
5.solar charge controller calculation
Thank you for your question, however I have already explained the entire process in the above article for quick calculations…
You have calculate the solar panel watt peak rating by depending on load list. You did not considered the amount of power required to charge the battery. Wil that design able to fully charge the battery while it supply the power to inverter ?
I have shown how to calculate the Ah value of the battery and the optimal current required for charging the battery in 5 hours.
Dear sir,
can you help me that problem
In pv system the distance betweeb the solar PV module is 10metres. The system voltage is choosen to be 12VDC. the PV module and battery are connected by copper cable 2.5mm² cross section area. estimate voltage drop in the cable if it is carrying 3.5A current. What would happen if the cable of 1.5mm² cross section area as used (Assume density of cable is 1.67×10^-8)
Hello Daudi, the calculations can be time consuming, you can try the following software instead:
https://www.homemade-circuits.com/56492-2/
Hello sir,having a solar rating 250w what is the size of charger controller needed and the number of batteries plus their rating
Hello Peter, please provide the voltage and current specs of the solar panel?
thank you mr.swagatam for your articles, my name is Mudasir and I’m a civil engineer by profession. I have a passion for electric and electronic things since my school days and I am always working on some simple circuits etc repairing day to day electric appliances myself. Recently my active project Is development of Rc based lawn mower for which all the parts I have ordered online. however I would need your help in sharing me a circuit diagram for a hybrid solar inverter system of about 6 kilowatt for home use. I have 20 solar panels of 300 watt installed for submersible water pump which works on 3 phase and is controlled by a VFD SOLAR CONTROLLER
Thank you Mudasir,
Can you please provide more details regarding all the features you would require in this hybrid solar inverter system, then I can try to figure it out, and design the complete circuit for you…
thanks for your response, the features include
load 6.2kw
AC GRID LINE INPUT 160V TO 220V @50 Hz
Dc pv input mppt range 90 volt to 450 volt
charging current 40 to 100 amp
out put : pure sine wave
additional features optional built in bms, lithium battery activation, wifi/ gprs connectivity
Thanks, can you please try the following H-bridge inverter circuit and check its response:
https://www.homemade-circuits.com/ir2111-h-bridge-inverter-circuit-with-soft-start/
If you succeed then we can proceed with additional features like MPPT…and upgrade current capacity…
Why did you base your SCC calculation on a 100-watt panel? You have computed it as 200 watts, right? i.e. 1,000 Watt-hours / 5 hours sunlight = 200 Watt solar panel.
The actual requirement is 100 watt but only if sunlight is available for 10 hours, but since 10 hours is not feasible, we have considered 5 hours, which calls for a 200 watt panel. This will charge the battery optimally in 5 to 10 hours.
Hi Mr. Swagatam,
I reside in Western Australia where we get the best sun throughout the year.
I am interested to build up a tilted solar power panel that could keep pointing to the sun ray at 90 degree.
I would be able to construct the tilted revolving base for the panel, but need your expertise advise as follow:
1. Could you provide the complete set of the MPPT Solar Charge Controller and the inverter? If not, then please advise which is the most reliable brand to purchase in Australia. Thanks.
2. How many panels (as minimum as possible) with the highest power rating do I need for the following loads:
(a) 1 x 1.5 Air-conditioner operating mostly from 10 am to 6 pm, summer and winter days
My backyard is huge, with 500 c.m. free space for installing any rotating panel assembly.
(b) 1 x 2000 watts storage water heating tank of 50 gallons capacity
For all other loads, I don’t mind to get regular supplies from the power grid.
3. Please also advise the most suitable panel size for maximum efficiency.
Kindly advise all prices and delivery lead-time, if you could provide.
Thanks for help.
John Lee
Hi John,
I do not have a full fledged working design of an MPPT in my blog, so I may not be able to help you with that. I think if you Google a bit regarding MPPTs you may be able to find many good options online. I personally do not have much experience with the MPPT brands available in the market.
As far as the solar panel is concerned, the following calculations can provide an approximate idea regarding the panel wattage.
1500 + 2000 = 3500 watts x 8hours = 28000 watt hour
assuming peak sunlight is available for 5 hours, we get
28000/5 = 5600 watt solar panels.
Hello,
I have a 5.43 KW Solar system installed. The solar output is through an inverter and then to a breaker box to a 40amp Breaker. My question is, I would like to add another inverter and more panels with a separate system but to the same Breaker box. Can I install two 20 amp breakers to replace the 40amp breaker. There is no more room on this breaker box to add a separate breaker box. How do I determine if a 20 amp breaker will be enough for each system? First system 5.4 KW, Second system is 3KW
Thank you!
Hello, you can divide the 5.43 KW with the voltage of the panel to get the required maximum amp rating for your breakers. If your existing breaker is rated at 40 amps then adding more panels and inverters would demand even higher rated breakers than your 40 amp breaker.
This I all I need for my basics in solar power installation/estimation
Really helpful, God bless the writer
Thank you, glad you found the post helpful…
Sir,
Thank you very much for being so generous. God will bless you more with deep knowledge.
I want to know sir, For a 5KW System,6KVA PCU and load is 4KW, How many 2V ,C10 batteries required and what will be its Ah ????
Awaiting Your Valuable Response Sir…
Abhishek,
you will require 3 such batteries which may give aback up of more 1.5 hours for a 4kva load
Hi Sir Swagatam;
Thank you for sharing your knowledge with us. However, I really acknowledge that I am short in understanding your illustration because I have no formal education in Electronics. I and my wife plan to DIY install Solar Power as an alternative source of energy on our home. Luckily I found your article online which we really need on what and how can we implement our plan. Can we request your help to compute for us what size of Solar Panel, Battery, Charge controller and Inverter we need for our project based on the following load/s we currently have?
1 Fridge – 95W – 24/7/365 continuous running
5 Wall fans (50W each) 250W – 2 runs for 10-12 hrs/day
4 laptops (65W each) 260W – 3 runs for 12 hrs/day
2 LED Lights (36W each) 72W – runs for 3 hrs/day
1 Rice Cooker 450W – 3 hrs/day
1 Water Heater 600W – 20 mins/day
1 flourescent lamp 20W – 1 hr/day
1 Water pump 450W – 30 mins/day
1 Washing Machine 400W – 1 hr/week
Approximately/Roughly we have 2,700 watts load but not all runs continuously.
We express our gratitude as early as this time for your generosity.
Marlon Joseph Laurel
Philippines
You are welcome Marlon, I will try to calculate it for you!
It seems we can assume on an average 30% of 2700 watts would be always running 24×7, then this would call for a 810 x 24 = 19440 watts
Since the wattage is high I will advise using a 24 V or 48 V inverter with battery. So considering 5 hours of peak sunshine on a average the solar panel will need to be 19440 / 5 hours = 3888 watts, and this should be rated at 36 V for charging a 24 V battery. The current will depend on the type of battery selected.
Assuming a 24 V system, the battery will need to be 19440 / 24 = 810 Ah @ 24 V
Inverter can be a 1kva or 1.5 kva at the most.
Charge controller will depend on the battery type.
Please let me know what will be the battery like, Li-Ion or lead acid
Sir Swagatam,
Thank you very much for being so generous. God will bless you more with deep knowledge.
The most common battery here in our Province in the Philippines is Lead Acid battery and that’s is what I am planning to buy unless I can buy Li-Ion battery online or somewhere in Manila.
Will it be okay if I buy 2 x 2000W Solar panel and be connected in series to meet the 3880 watts rated 36 V to charge the 24V battery?
By the way sir, how many batteries will it be for 19440/24=810Ah @24V? will it be 1, 2, 3, 4 or 6 batteries in parallel connection?
1KVA or 1.5KVA inverter means 1000W or 1500W?
Sorry for these additional queries sir because I am not knowledgeable in electronics. I just wanted to ease the heavy monthly bill we have here in the Philippines.
Marlon
No problem Marlon,
The panels must be able to provide 4000 / 60 V = 66 amps for charging the 810 Ah battery, which must be actually 1000 Ah, to ensure some additional margin. This means the solar panels must be rated at a net value of 60 V, 60 to 70 amps, which can be configured as per convenience.
For a lead acid battery, the charge controller must be a 3-step charge controller, with SMPS buck converter 60 V to 30 V with automatic cut-off
You can configure of 24 V 1000 Ah by any possible means, either by using 24 V batts in parallel, or by using 12 V batts in series/parallel connections.
Please note that the above calculations are only assumed approximately, therefore could be some errors in this, but we can always upgrade it if it is required.
Yes the 1kva = 1000 watts approximately and so on.
If the estimated figures are higher than the present requirements, then it can be an added reserve facility that could be utilized some time in future for operating additional electrical appliances.
Sir Swagatam,
Thank you so much for your guidance. I will be very happy to inform you once our project is done. Should you wish to visit my Country, the Philippines, in the near future I will be very glad to assist you or be our guest in our humble home. Just a humble gesture of reciprocity for your generosity.
By the way sir, I have 2 motors that i have been keeping for a while with the intent of using them for DIY project. 1 is an induction motor, 135W, from our old washing machine and the other 1 is a DC motor which can produce electricity of up to 230 V, 10A.
I am planning to use my induction motor to drive my DC motor, using pulley and pump belt so it can produce electricity, as reserve power.
This is my planned schematic:
12V battery > Inverter > Induction motor > DC motor
then…
DC motor > battery charger/charge controller > 12V Batteries(including the battery that runs the induction motor) > 12V to 1000W Inverter (?) > Load/s
Would such schematic be possible, sir?
Thanks again!
Marlon
Hello Marlon, your idea of using the motor output back to the batteries so that the system can work in a perpetual will not work, due to the huge losses that would happen during the conversion of the power from one form to the other…
Solar charge controller calculated should be 200W /12v, isn’ it?
Very insightful.
Hello Sir. I have a 20 amp MPPT charge controller. Battery is about 9’ from controller, what size wire is needed.
Thank you
Rick
Hello Richard, you can try the following software to calculate the wire thickness:
https://www.homemade-circuits.com/56492-2/
Dear sir
I have been visiting your tech. site regularly.I am not here to ask question but to say thank you so much for sharing these invaluable lessons free of charge.Many Technicians out there would not do it.How i wish you form a marketing outlet for sourcing electronics components, equipments and books.If that is your related field,and for those us with some electronics knowledge,it will be highly welcomed if you delve into programming.I mean ic programming lessons.
Once again i say thank you so much.
Thank you Dear Patrick, I appreciate your thoughts. I too want to upgrade my knowledge and innovate my website with new features but due to lack of time I am unable to proceed with any of these ventures, although I am always trying my best.
Hello Swagatam,
I am working on a solar car project and need some guidance regarding the number of solar panels required and their specifications.I want to run a 5-6kW BLDC motor directly through the solar panels,i am not sure about the approach so it will be of great help if you can throw some light on it.
Hi Karan, If you implement the steps mentioned in the above article you will be able to get the answers to your questions correctly. Along with load specifications, there are a few other parameters which you will need to include in the calculations. Please try it and let me know if you have any problems.
Hello sir.hop u fine.i have a 50ah solar battery.my panel is 120w.my load at night is only 50w TV,roughly 70w.problem is when I power on my inverter with TV on the battery drains from 13.4v to 12.3v in that moment.then inverter goes off after only 2hrs not even 4-5hrs I expected.please help sir,am using a computer ups as inverter….
Yusuf, to get 5 hour back up for 70 watt load, your battery must be rated at 50 Ah. If your battery is 60 Ah, then check the current consumption by connecting an ammeter in series with the battery positive, it should be around 6 amps at 70 watts, if it is higher then either your inverter is malfunctioning or your load is above 70 watts. If it is 6 amps then your battery has gone bad.
Thanks so much. This article looks much educative
Thank you, Glad it helped you!
Good morning, please I have 96 batteries of 12v 150ah With inverter of 48v. Please how many watts of solar panel will be required? To charge it effectively?
What is the energy demand or load
Hi Adekunle, the solar panel specs will depend on how the batteries are configured, and the number of batteries connected in series and parallel. If you specify this then I can give you a rough idea regarding the solar panel capacity.
Hello Swagatam, I’m trying to figure out roughly what I’ll need in battery size and solar panel size. I’ll be powering music amplifiers and laptop, with a total draw of about 8 amps AC, using a 1500W inverter connected to a 12V battery. I’ll need a minimum of 5 hours run time, with the solar panels charging the battery as I go.
So my question is, will a 100Ah 12 volt SLA battery be enough, and if so how much solar panel wattage will I need to keep the battery going for 5 hours under my load? I’ll be using the amplifiers at a volume you’d expect in a very small venue.
Thank you!!
Hello Glen, I think the calculations given in the article quite matches your requirement. So a 200 watt panel is what you may need for your application.
A 100 Ah battery should work fine.
Hello , I would like an estimate of how many panels and battery’s i might need for an all electric 40 square meter house . The hot water heater is only 20 liters , the lights are LED , the stove top is induction and the oven is like a normal oven .The frig is a single door. The water pump is demand pump and a computer AIO. There are other appliances such as kettle for water , rice maker , toaster , oven and microwave . all which could be removed or not. Cheers, John
Hello Mr Swagatam
I need to install 100 watts street light with solar panel.
Can you advise me which type of battery I should use and is it 100Ah 12V enough?
Siva
Siva, if the light is also 12 V then 100 Ah will be enough, provided the panel gets vertical sunshine at least for 8 hours.
God day sir, I really appropriate this article, and I benefited from it, my question is if the system voltage is 24v how the calculation will be for total wattage of 2000w.thanks sir, I am expecting the answer via my email