how-much-kwh-From-Solar-Panel
LAST UPDATED ON October 19, 2018

Solar panels are some of the best innovations in these recent few decades. They allow us to power our homes in a very cost efficient and Eco-friendly way, and can even help us save money in the long run. In case you are wondering how much power (kWh) solar panels put out and how many solar panels an average household needs, stick around because that is exactly what we are here to talk about right now.

What are the Major Factors that Will Affect the Electricity Being Produced by a Solar Panel?

When it comes to the different factors that will affect how much electricity is being produced by each solar panel, there are a few different things to keep in mind.

Size

The first factor that will determine exactly how much electricity a solar panel produces is its size. Now, this might sound pretty obvious, but it is very true none the less. Simply put, a solar panel that is twice the size of another, should in theory be able to absorb twice as much sunlight, therefore producing twice as much electricity as the smaller one.

Material

​The next factor that will affect the amount of sunlight absorbed and energy produced by a solar panel is the material it is made out of. Solar panels can be produced with various materials, some of which are more efficient than others. For this particular example, we want to talk about two main types of solar panels.
One of the best types to go with is the monosilicon cell panel. They have higher production costs, but are very efficient. There are also polysilicon cell panels, which cost less to make, but produce more waste and are not as efficient as the monosilicon option. However, recent innovations and research have led to polysilicon panels being almost as efficient as monosilicon models.

Amount of Sunshine

Of course, one of the really important factors that will affect the power output of your solar panel is how much sun it manages to get on a daily basis. After all, solar panels use sunlight to produce energy, so the amount of sunlight will directly affect the final power output. Keep in mind that solar panels don’t need direct sunlight per say; they can absorb light through cloud cover, but obviously being in direct sunlight is much better.

How to Measure the Efficiency of a Solar Panel

Something that you need to be aware of is that solar panels are not 100% efficient. In other words, not all of the sunlight they absorb is turned into usable energy for your home or business. Solar panels used to have an efficiency level of about 6% to 10%, but now with recent innovations, they can be up to 30% efficient or more.
Let’s find out how to measure the efficiency of a solar panel. Do keep in mind that solar panel ratings are often not 100% correct and there is some room for error here. So, when calculating efficiency, you will want to count with a deviancy of ± 2%.

  • 1
    The first thing you will need to do is to multiply the length and width of the solar panel to figure out what overall surface area of the panel is.
  • 2
    Figure out what the power rating of the solar panel is (in watts). This is the name plate rating.
  • 3
    You need to divide the number of watts at which the panel is rated by the total surface area of the panel. For instance, if the surface area is 1,500 square meters, and the rating of the panel is 250 watts, you would divide 250 by 1,500 and then multiply by 100 to find the percentage. For this example, the solar panel in question would have an efficiency rating of 16.67% (250/1500) x (100) = 16.67%

How is a Solar Panel Power Rating Calculated?

Ok, so you probably want to know what the power rating of a solar panel is. The power rating is how much power each and every single solar panel can produce for your home. This is very important to know, because it will allow you to gauge exactly how much of your electricity needs can be met by the solar panels that you have.
There is a specific calculation formula that you must use to determine the power rating of your solar panels, and it is somewhat complicated, so we will do our best to explain it in the simplest terms possible.
The formula that you need to use to calculate the power rating is as follows; E = A * r * H * PR. Let’s talk about what each of these variables stands for. Once you have figured out what the value of each variable is, simply plug the values into the equation and you will have your final power rating.

E (Total Amount of Energy in kW)
This is the total amount of energy in kilowatts that your solar panel produces. This is the end game of the equation, what you are looking to figure out.

A (Total Surface Area)
This is the total surface area of your solar panels. To figure out what the total surface area is, simply multiply the length and width of the solar panel by each other.

​r (Efficiency Rating)
This is more or less the efficiency rating of the solar panel. This is what we figured out how to calculate in the section above. Once again, if the panel in question has a yield of 250 Wp and is 1.6 meters squared in surface area, the overall efficiency would be 15.6%

​H (Global Radiation Value)​
This is the global radiation value, or the average amount of sunlight-based radiation which your area of the world receives. For instance, in Norway, the average is 200 kWh/m2 per year, while in Saudi Arabia it is 2,600 kWh/m2.y. To get this value, you need to figure out the solar radiation data for where you live.

PR (Perfomance Ratio)
PR stands for the performance ratio of the solar panel in question. There are various power losses which occur when solar panels absorb light, light energy that is not converted into usable power due to various processes and pieces of equipment.
Inverter losses can account for up to 10% in losses, temperature for up to 20%, DC and AC cables for up to 6%, and there are various other factors too. To figure out the power rating, or exactly how much power your solar panels will produce, you need to figure out what the performance ratio is first.

How Much Energy Does a Solar Panel Produce Per Square Foot?

Figuring out how much energy is produced by each square foot of solar paneling is important when it comes to determining the size of the solar installation you want to put on your roof. Simply put, once you know how much power each panel puts out, simply divide it by the square feet of the panel. For instance, if you have a panel that puts out 265 watts, and is 65.4 by 39 inches in size, the energy produced per square foot would be around 15 watts. While this does not sound like very much, square feet do add up pretty quickly.

How Much Energy Can a Solar Panel Produce Per Day and Per Month?

Ok, so now that you know exactly how much power a single solar panel creates, you can figure out how much power it can produce per day and per month. So, if you have a 250 watt panel, you need to multiply those watts by the amount of usable sunlight your roof gets in day. For example, in the US, the average amount of full usable sunlight per day is about 4 hours.
Therefore, to figure out how much power the panel produces in a day, simply multiply the 250 watts by 4 hours, which comes to 1000 watts per day. Now, to figure out how much energy is produced per month, multiply those 1000 watts by either 30 or 31 days, depending on the month of course. On average you can expect a solar panel to generate around 30,000 watts per month.

How Much Power Do My Electrical Appliances Need?

This is a very vague and somewhat difficult question because some appliances are very energy efficient while others are not. This becomes crucial when you are looking for portable solar panel systems for your RV.  For instance, an average fridge will use between 1 and 2 kWh, with older models using much more. Water heaters, depending on the family size, can use up to 4,500 watts; other appliances that use a lot of energy include heaters, dishwashers, washers, dryers, and others. If you have a big household, chances are that you might not be able to power your whole home with solar panels. In case of unexpected power outage, it will never hurt to have a stand-by portable solar generator around in the house.  

How Many Solar Panels Does An Average Household Need?

Once again, this is a little hard to figure out because it depends on how many people are in the home, how large the space is, and how many appliances are in use. On average, a normal household will use around 37 kWH per day. So, if you have solar panels that each produce 1 kWh of power per day, you would need a full 37 solar panels to fully power your home. However, keep in mind that there are many factors at play here, so this is really only a rough estimate.


Conclusion

As you can see, there is quite a bit of math and science involved to calculate how many kWh a solar panel can produce per day. There are many different factors which can affect the final power output of your solar panels, so make sure to do all of the necessary research before putting up your own solar installation. Yes, these systems are usually quite efficient, the costs have been lowered, and they are eco-friendly as well. For all intents and purposes, solar energy is the future of green energy production.

That’s it! Thanks for stick around till the end. I hope the math won’t make your head spinning. If you’ve found this post useful, please share this article with your buddies and let us know in the comments below or leave a comment on our social pages.

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