How Much Output Do You Get From Solar Panels?

There are three different terms that people may be referring to when they use a term like 'solar panel power output':

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

  • The energy production of a 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 'big' 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 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 2020?

Modern solar panels are made from silicon solar cells, either monocrystalline or polycrystalline silicon solar cells. Panel efficiency is 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 it is best to separate solar panels into 60-cell solar panels and 72-cell solar panels.

60-cell solar panels are typically 1700cm tall by about 900cm wide and they have a power output in standard test conditions 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. They are more commonly used for solar farms. Even today, manufacturers are already working on 500-600 watt panels and testing them for future use.

 

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.

 

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 how 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 generate 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 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 or quarter is reflected by the amount of your electric bill.


 

For example, leaving an average 50-watt light bulb on for one hour equals 50 watt-hours. This means that twenty 50-watt bulbs equals 1 kilowatt-hour (kWh). Kilowatt hour is the unit of measure at which your electricity retailer can charge you for the electricity used.

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.

 

It is not a surprise that suburbs in Western Australia and Queenland have among the highest solar installations in Australia. See https://www.econnex.com.au/suburbs-generates-more-solar-power-than-the-big-cities/

 

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. They have lower rate of light induced degradation (LID) and a better temperature coefficient than polycrystalline panels.

  • 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.

  • 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. The real benefit is the ability to form or mould this material into long sheets that can be applied like roofing materials on south-facing surfaces.

Latest Solar Technology

Here we highlight the latest solar panel and PV cell technologies used by leading manufacturers. The best quality panels are expected to perform over a 25 year life. The manufacturers of these panels use the latest solar cell innovations. Their aim is to develop the most efficient and reliable panels with the longest life and highest performance.


 

PERC - Passivated Emitter Rear Cell

Has a more advanced cell architecture using additional layers on the rear side of cell to absorb more light photons. PERC technology boosts efficiency through the addition of a layer to the back of a traditional solar cell. PERC technology is less costly to manufacturer and is favoured by most solar manufacturers.


 

Bifacial -Dual sided panels and cells

Bificial cells absorb light from both sides of the panel, in the right location and conditions, and can produce up to 27% more energy than traditional monifacial panels. They typical use a glass front and clear rear polymer backsheet to encapsulate the cells which allows reflected light to enter from the rear side of the panel.


 

Multi Busbar – Multi ribbon and wire busbars

Busbars are thin wires or ribbons which run down each cell and carry electrons through the solar panel. A normal panel has 3, 5, 6 busbars. Multi busbar systems have up to 12 or 16 thin round wires. They provide lower resistence and shorter path for the electrons to travel – resulting in a higher performance. Furthermore, if there is microcracking in the cell, having more busbars allows less chance of cell hotspots so that electrons can flow freely.


 

Split panels – using half cut cells

This effectively splits the solar panel into 2 smaller panels which work in parralel. Therefore, the width of busbars are reduced by half and reduces cell shading, losses and increasing efficiency.


 

Shingled Cells – overlapping cells

Shingled panels have slight overlapping of each cell strip which hides the single busbar – interconnects the cell strips. These shingled cells are connected in parrallel -reducing the effects of current loss through shading.


 

IBC – Interdigitated Back Contact cells

These cells have a grid of 30 or more conductors integrated into the rear side of the cell – unlike standard cells which typically have 4-6 large visible ribbons busbars and multiple fingers on the front side of the cell. IBC cells don't shade the cell and don't reflect some of the light photons. The world's most efficient and best performing solar panels use IBC -N type cells, are also the most expensive because of their manufacturing costs. Examples are Sunpower and LG panels.


 

HJT – Heterojunction cells

Uses a base of common silicion with additional thin film layers of amorphous silicon on either side of the cell. It has multi layer heterojunction cells to increase efficiency to capture the different spectrums of light. Known to be the second highest efficiency because of its low temperature coefficient.


 

Perovskite Solar Cells

Still in the laboratory in testing and development, perovskite solar cells are showing promise with efficiency close to 30%. So far they are a low cost to produce as an alternative to silicon cells, but need to overcome other challenges, like handling moisture content for it to be competitive with existing panels. For more information, see

https://www.energy.gov/eere/solar/perovskite-solar-cells

Reverse Solar Panel

Researchers in Singapore have developed the concept of harvesting energy in the presence of shadows. They call it 'SEG' shadow-effect generator. So far created on a device, it gives an advantage over commercially available solar cells by operating in dark areas. Can this technology be used for the wider solar PV industry? Time will tell! See more details here.

 

Can you increase the efficiency of a solar panel?

As briefly described above, and the strides taken within the industry being made daily, there isn't much you (as the home owner) 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 with the expert assistance of solar installers or accredited designers.

 

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 energy retailer for electricity will all influence power production you will need from your solar array to save on your power bill.

 

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

Call us for a free solar assessment!

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