One of the most important questions you should ask yourself before investing in a new solar system is how much electricity it will produce.
You see, the answer to this question is relative, and what applies to me, may not necessarily apply to you.
The answer to this question starts to become even more critical once you begin calculating rough payback periods.
After all, solar systems are not cheap.
In this article, we will teach you how solar panels convert sunlight into electricity and how you can calculate the amount of electricity you could come to expect from a solar system installed on your particular roof.
How do solar panels produce energy?
Solar panels convert sunlight into electricity via a method known as the photovoltaic effect.
In order for the photovoltaic effect to take place, a solar cell (or panel) needs to be exposed to photons (which is simply small bundles of electromagnetic radiation).
These photons are actually absorbed by the solar cell through two different types of semiconductors. The p-type and the n-type. These two semiconductors are joined together to create a p-n junction.
When you join these two types of semiconductors, you allow an electric field to be formed in the region of the junction as electrons move to the positive p-side and holes move to the negative n-side.
This electric field forces negatively charged particles to move in only one direction, the opposite for positively charged particles.
This whole process eventually results in electricity production.
How many solar panels do I need?
The absolute easiest way to determine how much electricity a solar panel will produce, is by using an online solar calculator.
There are so many intricate equations which affect the amount of energy produced that doing all the calculations yourself is a hard bit of work.
However, if you insist in doing so, there is a slightly more simple/rough way to determine the amount of panels you would need in order to offset your energy consumption.
You can do this by sort of reverse engineering your specific scenario.
The formula looks as follows:
So let's create a working example with the formula above.
You live in California and consume 890 kWh per month. At this location you would receive about 5.250
Now we can simply use the formula above to establish the number of solar panels needed to offset our consumption.
890 / 161 = 5.5 kW
5.5 kW x 1000 = 5,500 watts.
5,500 watts / by 400 watts = 13.75 (400 watt) solar panels are needed to offset your energy consumption at this location.
If you would like to work out your own solar panel requirements, simply repeat the above formula with your own data input.
How much electricity will my solar system produce?
Now, to understand how much electricity your solar system will produce, you need to know quite a few other factors about your solar system.
Most of these factors are fairly complicated, so much so that we don't recommend working it out yourself, but instead, using a solar calculator.
There are many free solar calculators online, but if you are interested in getting the most accurate information fast you should use PV Watts calculator by NREL.
Wirth this calculator you can simply enter your solar system size (which you should know using our formula above), and your location. Then the calculator does the rest.
Here are a few working examples:
- Location: New York City
- Solar system size: 10 kW
| Month | Solar Radiation
(kWh / m2 / day)
|
AC Energy
(kWh)
|
|---|---|---|
| January | 2.90 | 767 |
| February | 3.92 | 921 |
| March | 4.57 | 1,164 |
| April | 5.41 | 1,278 |
| May | 5.41 | 1,303 |
| June | 5.96 | 1,362 |
| July | 6.17 | 1,435 |
| August | 5.88 | 1,372 |
| September | 5.16 | 1,192 |
| October | 4.06 | 987 |
| November | 3.06 | 749 |
| December | 2.41 | 626 |
| Annual | 4.58 | 13,156 |
- Location: California
- Solar system size: 8 kW
| Month | Solar Radiation
( kWh / m2 / day )
|
AC Energy
( kWh )
|
|---|---|---|
| January | 4.74 | 936 |
| February | 5.63 | 996 |
| March | 6.91 | 1,334 |
| April | 7.55 | 1,380 |
| May | 8.16 | 1,517 |
| June | 8.43 | 1,491 |
| July | 8.08 | 1,443 |
| August | 7.96 | 1,415 |
| September | 7.46 | 1,318 |
| October | 6.43 | 1,216 |
| November | 5.14 | 971 |
| December | 4.44 | 885 |
| Annual | 6.74 | 14,902 |
- Location: Idaho
- Solar system size: 6 kW
| Month | Solar Radiation
( kWh / m2 / day )
|
AC Energy
( kWh )
|
|---|---|---|
| January | 2.55 | 392 |
| February | 3.76 | 519 |
| March | 5.06 | 774 |
| April | 6.52 | 934 |
| May | 6.69 | 975 |
| June | 7.22 | 982 |
| July | 7.62 | 1,047 |
| August | 6.98 | 960 |
| September | 6.05 | 822 |
| October | 4.34 | 634 |
| November | 2.96 | 427 |
| December | 2.09 | 326 |
| Annual | 5.15 | 8,792 |
Final thoughts
As you can see, the amount of electricity your solar system produces largely depends on where you live, and what size your solar system is.
Other factors such as module type, array type, system losses, tilt angle and azimuth affect your solar systems energy output too.
These factors greatly increase the complexity of the calculation and that is why using a solar calculator over your head, usually works out best.
