May 30, 2013

How to Calculate and Match Solar Panel, Inverter and Battery Charger Specifications for Acquring Optimal Results

The following post explains through calculations how to select and evaluate the right solar panel, inverter and charger controller combinations for acquiring optimal results in the form of free electricity.

For convenience, let's believe you possess a a hundred watt gadget that you would like to operate with free of charge solar power for ten hours every night.

To determine how large solar panel, batteries, charge controller and inverter it is necessary to have, observe the below conditions.

1. Estimate the amount of electricity required. 100 Watts x 10 hours = 1,000 Watt hours. Which is the absolute power that is necessary.

2. Next figure out how large solar panel you really need. Depending on a ten hour day of luminosity, the approximation is straight forward:
1,000 Watt hours / 10 hours sunlight = 100 Watt solar panel.

The simple truth is that nearly all the summer time days or weeks provide roughly 15 hours of sunshine and winter season you receive roughly 4-5 hours of natural light. Invariably select the worst case predicament for
your solar panel. On those grounds, choose a winter season day of sunshine.
1,000 Watt hours / 5 hours sunlight = 200 Watt solar panel.

(Based on normal United States daily sunlight .)

3. Calculate the optimal size of the batteries which might be essential. 1,000 Watt hours divided by 12 Volts = 83 Amp Hours of reserve battery power. 1,000 / 12 = 83.3
A typical marine deep cycle battery works nicely in this case. Choose much bigger battery to rest assured, assume 100 Amp hours power.

4. To estimate how big solar charge controller you might need, consider your solar panel energy specs, which happens to be a hundred watts divided by twelve Volts.
100 / 12 = 8.3 Amps.
Desirably choose bigger sized units, and therefore utilize a ten Amp solar charge controller.

5. Determine what capacity inverter can be used. That's the hassle-free aspect. You might want to energize a a hundred Watt load, therefore choose an inverter which includes
no less than a hundred Watts steady power standing.


  1. hi sir i have a question that i have a 55w solar panel 50ah lead acid batery i dont have a controler so for how long the batery will be full charged? and also i can run 2w 5 bulbs,40w tvand dvd for how many hours? and also what is the suitable charge controller needed? thanks

    1. Without a charger controller it would be dangerous to charge the battery, or drive any gadget.... not recommended.

  2. Dear Mr. Majumdar

    Can you help me in installing a solar panel at home?

    I have the following data:

    Solar panel wattage: 216 watts
    Electricity required in our home: 106 watts
    Hours of use: it doesn't matter to me as long the hours wont go below 10 hours.
    Hours of sunlight (based on the normal daylight ): Max.- 7 hrs.; Min.- 6 hrs

    Can you fill in the blanks? :
    battery: voltage:___; amp-hours:___
    inverter: wattage:___; voltage: 220

    Can I ask if you can make me a solar charge controller out of the data above?

    And can you add a function to the solar charge controller? : If the sun has enough light,
    the inverter will get the source from the solar panel while the battery is being charged.
    Then the moment the cloud dims, in which the solar panel can't produce enough voltage,
    the relay will change the inverter's source, which is from solar panel to battery. With this function I can protect the appliances from low voltage and use the solar panel during daytime.

    thanks a lot for your kind consideration!!!!

    yours truly
    Eshkariel Tapiador

    1. Dear Achiless,

      I'll try to do it and respond soon.

  3. Replies
    1. Good day Eshkariel,
      you can try calculating the parameters with the help of the data given in the above article. It isn't very difficult if you see.

      I'll try to design the solar charger that you have asked and will let you know soon, pls remind me if i forget, though:)

  4. This comment has been removed by the author.

    1. Good Morning Eshkariel,

      Your calculations look OK to me.

      You can try the inverter that's been covered in this article although it's not a pure sine wave, just a modified one.

      transformer rating could be = required wattage divided by available voltage, this will give the amp rating for the trafo.

      Battery could be rated at = required wattage divided by voltage,this will give the AH of the battery, but make it twice at least for a reasonable back up time.

  5. Replies
    1. eshkariel, I think it's already published in my blog, you can refer to this post for more info:

  6. hello sir I want to run 100 watt inverter on solar panel so how many watts panel require for it???

    1. hello kanu, you can try a 25 watt panel and a 25 AH battery

  7. hello sir I am student from Anand,Gujarat, I
    want to make 100 watt solar
    inverter,so how many watts solar panel and
    battery require for it?

  8. Hello sir. Can you suggest me what are all the components to be bought by me including their grades as I am not much aware of electrical components

    1. Hi Nandula, please specify your requirement specifications....only then I would be able to suggest.

    2. My requirement is making a speed restrictor for vehicles.

    3. you can try the following circuit

  9. I hv a 1000 wt invetor and a 240 solar panel and battery but if I try to connect the invetor it just says faulty Wat cn be the problem with it

    1. your specs are not sufficient for judging the fault...


Swagatam Majumdar
Swagatam MajumdarHi Friends, Welcome to my site, a place where you will discover a massive collection of electronic circuit ideas, mostly requested by the dedicated readers and exclusively designed by me for their customized application needs. I have posted more than 1100 circuit designs in this site, if you have a personalized circuit requirement you may feel free to request it through the comment box, if it seems feasible to me then surely you may find it published here with your credentials attached in the post, thanks and please keep reading

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