How Many Solar Panels Do I Need?

Now that you’ve started planning your DIY home solar power system, you may be wondering how many solar panels you will need to power your house.

In order to find out how many solar panels you’ll need, we need to answer a couple of questions first:

  1. How much electricity do you use now?
  2. How much can you save through conservation?
  3. How much of your own electricity do you want to generate?

Once you answer these three questions, it will be simple enough to calculate the number of solar panels needed to provide the power you need.


How much electricity are you using now? This basically boils down to one number: how many kilowatt-hours you use each month. This can be found on your monthly electric bill. This number, also known as KwH, is the unit that your power company uses to calculate how much you pay each month. The unit of one kilowatt hour represents a 1,000 watt electrical load that consumes power for one hour.

How much electricity can you save? Have you replaced your inefficient old incandescent bulbs with new Compact Flourescent Light bulbs? (“CFL’s”) How about your appliances, are they EnergyStar certified? Before you start your home solar power setup, you’ll want to reduce your electric usage as much as possible through conservation.

How much of your electric usage do you want to replace with electric power from your DIY solar panels? Most homeowners starting out with home solar power begin with the goal of producing 40% of their own energy with solar. As time goes on you can grow and expand your system by installing more solar panels. This will help you move toward your goal of generating 50%, 75% or even 100% of the electricity that you use every month.

So let’s use a concrete example. Let’s say you currently use 800 KwH per month. Then by replacing light bulbs, turning off electronic items when they are not in use, etc., you reduce your monthly usage to 600 KwH per month.

Then you decide that you will want to replace 50% of your usage with your own solar power. That would come out to 600KwH * 0.50 = 300 KwH per month.

Let’s assume that your location gets an average of 6 hours of sun per day. This takes into account some rainy and cloudy days. That’s 6 hours per day for 30 days = 180 sun-hours per month. In order to generate 300 KwH of solar electricity per month, we’ll need to have 1.667 Kilowatts of solar panel generation. That’s 1667 watts of generation capacity. If you have panels that generate 80 watts each, that will take about 21 panels running at 80 watts.

This may sound like a lot at first, but remember that you can start with even just one panel and get moving towards your goal of energy independence. You can easily add more panels as your time and budget allow.
Also, remember that there are now federal tax credits available that will refund you 30% of the cost of any solar panels, solar power inverters, charge controllers, and related solar power equipment that you may purchase.



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  2. april

    I need to generate 800 kWh during our rough months, we are looking at some panels that have maximum output of 235 watts by sharp…we figure that 8 panels is over the top and we should never run out of energy if we make this investment. I could not figure out the calculation to 1.667 , in the one up above but this is my info. Can you help us? Aug = 786 kWh, Dec-662 kWh, 788-Jan ; and my average is 745.33kWh per month. In Africa where I stayed we used complete solar energy.

  3. jeremy

    You will need roughly 4 Kw of solar panels (4000 WATTS) if you know how to use a soldering iron,then I would suggest searching ebay for solar “cells” and easily construct your own panels for around $300-$400 per 1 Kw. Depending on the protective enamle / frame and glass you choose to use. Hope this helps you make a sound investment. I hope I was able to help you get the power you need without having to pay to much and getting turned off to solar energy.

  4. jeremy

    Ebay also has cheap Grid Tie Inverters and battery charge controllers so you can tie into your homes electricity and so you can have a batttery bank for night time and stormy day. :-)

  5. jeremy

    The above calculation hje did was for 600 Kwh per month after lowerinf consumption through conservation. It also only shows what you will need to power Half 1/2 of 600 Kwh. So 1.66Kw would only be enough for 300 Kwh per month.

  6. Certainly, but people need to understand that adding Solar on their house is an purchase that could increase the long term worth of their building if / when they decide to sell. With the environment the way it is going we are not able to overlook any product that offers zero cost power at no cost to both the buyer and more notably the world!

  7. Fred

    November 7, 2012 at 5:22 pm
    You will need roughly 4 Kw of solar panels (4000 WATTS) if you know how to use a soldering iron,then I would suggest searching ebay for solar “cells” and easily construct your own panels for around $300-$400 per 1 Kw. Depending on the protective enamle / frame and glass you choose to use. Hope this helps you make a sound investment. I hope I was able to help you get the power you need without having to pay to much and getting turned off to solar energy.

    How did you figure she needed a 4kw hour system without knowing how many hours of average sunlight in her area?
    I know it was an estimation but can you show the math for it please?

  8. himu

    hello dear Jeremy thank you for your convenience and helping people who want to use green energy .
    dear I think the temperature is 100% important in this case .
    I wanna change the electricity source also can you help me please
    the temperature is between 30° up to 46° and have about 9 hour sun per day
    and need to 50kw per day and mostly about1200 kw.
    how many solar panels I need
    and how much money I should spend
    thank you so much

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  10. Alain Saadé

    good morning
    My name is Alain Saadé from Lebanon and I want to know if I can produce 600 A 24 h per day by using solar panels. If it’s possible can yo please tell me how much and what type of cells i have to use, the number of batteries, the coast of the system and the area that will be used by the solar panels.
    Thank you and best regards

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  22. joe gilman

    how many solar panels are needed for 4000kwh per month. Maryland area
    ground mounted.

  23. Robert King

    I use 300 Kw per 7 days or 1200 per month ave. How many solar panels do I need. I live in Deep South Texas. I have 12 hours sun a day or more in the summer. facing south. in the winter 8 hours in the winter. lots of sun.

    I would like to buy the new battery system that the tesla car owner is touting.
    Estimates is all I am asking. Tks.

  24. Sebin

    I have consumption of 150 kW /monthly and i want to assemble my own panel. I bought 100 pcs of 4.2watt cell with 0.5volt each. Can you please tell me what are the other equipmwnt i required like charge controller,battery,and inverter required to match the consumption.

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  28. Leo

    I use 850kw a mnth im haveing 19 panels put on my roof will i produce enough power and then some??

  29. fred

    This is a question,,,Im trying to figure out how many panels I will need to run my equipment, each unit takes 444 watts per unit , including the psu to power up the unit, im using a meter to check the rate,,it comes out to 0.80 per kwh, I want to hook up 50 units @444 watts per unit,, How many panels and equipment would it take, or if its to much ,, maybe use just 25 units, does any one have a answer,,, This would be off the grid……..

  30. fred

    Also I have 12 hrs. of sun here in ca. facing the south

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