Solar panel power output explained

Solar panel output is one of those phrases where people using it are often trying to describe different things. The three different things that people may be referring to when they use a term like 'solar panel power output' can be:

  • The wattage or capacity of an individual solar panel, measured in watts;

  • The energy production of an individual solar panel over a time period, installed in a specific place (measured in kilowatt-hours kWh);

  • The amount of energy generated by a complete solar panel system, either per day, per month or per year.

Let’s look at what each of these measures of solar panel output means and then ask the $10,000 question: How much electricity will solar panels produce on my house and how many modules do I need to cover my electricity bill? The amount of electricity produced by a solar panel can vary due to its dependence on three simple yet important components: its size, the efficiency of the solar cells the panel contains, and the amount of sunlight it absorbs.

What is the standard power output (wattage) of individual residential solar panels used in 2019?

Modern solar panels are made from silicon solar cells, either monocrystalline or multicrystalline (sometimes called polycrystalline) silicon solar cells. Both are similar in terms of energy output, although panel efficiency is typically slightly higher in monocrystalline solar panels.

The power output, or wattage of a panel, at standard test conditions, is generally what people are talking about when they refer to solar panel power output. Standard test conditions are when there is a cell temperature of 25C°, and 1 kilowatt per square meter of solar energy shining on the panel.

In terms of power output (measured in watts) it is best to separate solar panels into 60-cell solar panels and 72-cell solar panels.

60-cell solar panels are typically 5.4 feet tall by about 3.25 feet wide and they typically have a power output in standard test conditions of between 270 watts to 300 watts, depending on the exact efficiency of the cells in them. Only a few years ago power output of standard 60-cell panels was more like 250 watts, but improvements in technology have improved average panel wattages.

72-cell solar modules are physically larger, because they have an extra row of cells, and will typically have a power output of between 350 watts and 400 watts. These are less often used for rooftop solar as they are difficult to handle on a roof; they are more commonly used for utility-scale solar farms.

Even though the average size of solar panels hasn't changed in decades, their efficiency has improved drastically. When first used in the 1950s, solar cells only converted about 6 percent of the sun's energy into electricity. At that percentage, an array of 60 cells would only produce about 20 watts of electricity, hardly enough to power a small light bulb.

Modern solar cells are capable of absorbing about 20 percent of solar energy. The power rating of each panel is decided by combining cell efficiency with the size of each solar panel. This means that each panel can be rated to produce a certain amount of wattage.

How much power does a solar panel produce over a month or a year?

Solar panels are rated based on home much power they produce in ideal sunlight conditions and temperature conditions known as standard test conditions. This is defined as the maximum power rating.

The problem is that actual sunlight conditions aren't always at their peak. This means that the amount of electricity your home's solar panels will actually produce on any given day depends on several environmental factors:

  • The average amount of sunlight your roof might get daily or annually.

  • Whether recurrent shading, such as that from wind-blown tree branches, obscures direct sunlight from constantly hitting your solar panels.

  • The size of your solar panels and the level of efficiency the solar cells demonstrate at converting energy into electrical power.

Each kilowatt-hour is a unit of electrical energy equal to power (1,000 watts) multiplied by time (hours). The number of kWh your home uses every month is reflected by the amount of your electric bill. For example, leaving an average 100-watt light bulb on for one hour equals 100 watt-hours. This means that ten 100-watt bulbs equals 1 kilowatt-hour (kWh).

Do solar power panels generate more electricity in certain states?

Yes, solar panel power generation varies with the climate of the state, the number of sunlight hours, and the sunlight intensity that the panels are exposed to. This article shows the power output from solar panels in each state, per day and per year.

Do some solar panels produce more solar energy than others?

  • Monocrystalline solar panels: These are the most expensive and efficient panels on the market. The cells contain pure silicon and undergo a complicated process of growing long crystal silicon rods. The rods are sliced into nearly translucent wafers and formed into cells.

  • Polycrystalline solar panels: These panels are comprised of multiple polycrystalline cells. They're slightly less efficient and more affordable. The cells are processed differently, giving them the appearance of shattered glass. This product is also cut into very thin slices.

  • Amorphous solar panels: The cells are not crystals, but a thin layer of silicon secured to a base material such as glass or metal. While these panels are the least expensive, they also produce far less electrical power. This means you'll need more of them to equal the power output of either of the other panels. The real benefit is the ability to form this material into long sheets that can be applied like roofing materials on south-facing surfaces.

Can you increase the efficiency of a solar panel to output for electricity?

While strides within the industry are being made daily, there isn't much you can do to increase the efficiency of a solar panel beyond performing routine cleaning. Dust and debris, or snow, can affect the efficiency of panels.

How many solar panels will my home need?

Calculating the number of solar panels needed to power your home can be easily done online using a solar calculator. The size of your home, the location of your home, the amount of power you typically use every month, and the rate charged by your utility for electricity will all influence power production you will need from your solar array to wipe out your power bill.

Once you know the power output required and the climate where the solar panels will be installed, it is possible to0 work out the number of solar panels you need and how much solar panels will cost for your home.

Here is a link to an article showing the average number of solar panels to power a home in each state.

Calculate the number of solar panels you need to power your home

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