installing solar panels on the roof

How Much Energy Can A Solar Panel Produce?

The most common solar panels harness between 250 and 400 watts of power. Once
you get your solar installation quotes, you might see your solar panel output numbers,
next to the name of the panel, ex. “245W”, “300W”, or “345W”. These are the numbers that reference the solar panel’s wattage, capacity, and power output.

In addition, solar panels are rated depending on the amount of DC (direct current) power they are
able to produce. The output of a solar panel is described in units of watts (W), this
represents the panels calculated production under ideal conditions (i.e. the panel is at
the ideal angle, facing South, with optimal sun). You can derive the Wattage amount by
multiplying volts x amps, using volts to represent the amount of force of the electricity,
and amps to represent the aggregate amount of energy used.

It is common for a home’s solar panels to have power output ratings (POR) from 250 to
400 watts. Generally, a higher power rating is preferable when compared to a lower
power rating; because the less power one panel can produce, the more panels you will
need to power your home. Keep in mind, while pricing for a home solar system is
typically measured per watt, the materials needed to produce the required watts and the
installation time needed will affect the overall price for your solar system.

Let’s look at an example:

If your home is receiving 5 hrs of direct sunlight per day, you can calculate your solar
panel output like this: 5 hrs x 290 watts (example from a common solar panel) = 1,450
watt hours, or approximately, 1.5 kilowatt hours (kWh). Therefore, each solar panel in
your array would produce approximately 725,000 – 797,500 watts of energy per year,
which is equal to 500-550 kWh of energy per year.

What will affect my solar panel output?
There are three main factors that can be used in order to determine a solar panel's
output: cell efficiency, solar panel size, and various environmental factors.

The Efficiency of a Solar Panel

The first can be determined by the percentage of sunlight that a solar panel is able to
convert into usable energy. For instance, on average a solar panel can convert about 20% of the
sunlight it collects. This has led to an increase in the amount of wattage in a solar panel
(going from 290W up-to 400W). The higher your efficiency the more energy your panel
will be able to produce. Higher-efficiency panels will produce more electricity for your

The Size of a Solar Panel

The size of a solar panel can be determined by the amount of cells it has. Moreover, there are two
main solar panel size groups: 60-cell solar panels and 72-cell solar panels. The average
size of a 60-cell solar panel is approximately 5.4 ft tall by 3.25 feet wide, with an average
output of 270 to 300 watts. In contrast, a 72-cell solar panel is larger, with an output
between 350 to 400 watts.

Note: 72-watt panels are not typically used on residential homes, and are more suitable
for use on commercial solar projects, like solar farms.

Environmental Effects on a Solar Panel

At any rate, there are a few environmental factors that go into determining the output of a solar
panel. Which are: Natural obstructions, Location/ Angle, and the total amount of
sunlight hours your solar panels will receive.

Natural Obstructions

Firstly, natural obstructions can affect the amount of sunlight your solar panel array will have
access to, the most common being shading, often from trees, or higher neighboring
homes. In addition, it is important to remove anything that could be blocking your panels from
receiving full sun.

Angle/ Location

Secondly, the angle/ Location of your solar panels will impact their production. For this reason, it is ideal that
your solar panels be facing directly towards the sun. Of course, some roof planes are
not always perfectly angled for maximum production.

Sunlight Hours

Thirdly, sunlight hours will refer to the total amount of sun your panels will be exposed to under
perfect conditions. In fact, the more sun hours you have, the greater your solar panel output will
be. You can better understand this by comparing the amount of sunlight hours a state like California would have compared to a state like Alaska.
Note: both of these states have the ability to go solar.

Why is the efficiency of a solar panel so important?

To conclude, the higher a solar panel’s efficiency, the more power it can produce. If a
solar panel’s output is higher it will provide you with more energy that can be used to
power your home.

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