How much output do you get from solar panels?
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‘How much power do solar panels produce?’ is a question we often receive from consumers. In our experience, they could be asking about either of the following two things:
These are both crucial things to know for anyone interested in, or already using, solar power. The good news is that both of these concepts are closely related and relatively easy to understand.
Once you understand solar panel output, we can move on to asking 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 power rating tells you how much power a solar panel was designed to produce. It measures the wattage of a panel when it is operating at standard test conditions.
“Standard test conditions” is when there is a cell temperature of 77F° (25C°), and 1 kilowatt per square meter of solar energy shining on the panel.
In other words, a solar panel’s power rating measures how much electricity an individual solar panel will produce under ideal operating conditions.
Solar panels used on homes in 2023 generally have power output ratings between 350 and 450 watts of DC power per module.
Solar panel wattages have steadily increased over time. Just consider the fact that 400-watt solar panels are now commonly-used in home solar panel installations. The first residential panel with this level of power output, 400 W, only came out in March 2019 (it was released by SunPower, and it was very expensive); at that point, many homeowners were still installing solar panels that were between the 250 W and 300 W mark.
The reason for the growing power wattages of solar panels is due to improvements in solar panel efficiency. Higher efficiency means that you can produce more power in the same amount of space.
Higher efficiency solar panels are especially important when you are looking to install a residential solar power system on your home, but you have limited roof space. You can use fewer high efficiency panels to produce the same amount of energy as you could if you had used more lower efficiency panels.
The amount of electricity produced by a solar panel can vary based on three factors:
Even though the average size of solar panels hasn't changed in decades, their efficiency ratings have improved drastically. When first used in the 1950s, solar panels could only convert one-twentieth of the sun's energy into electricity. At that percentage, a standard-sized solar panel would only produce about 20 watts of electricity, hardly enough to power a small light bulb.
By contrast, modern solar panels are capable of absorbing around one-fifth of the solar energy that hits them, allowing a single solar panel to reach 400 watts of output or more.
The power rating of each panel is determined by combining cell efficiency with the size of each solar panel. This means that each panel is rated to produce a certain amount of wattage.
In terms of power output, it is best to separate solar panels into two categories: 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 have a power output in standard test conditions of between 350 watts to 400 watts, depending on the exact efficiency of the cells in them.
72-cell solar modules are physically larger because they have an extra row of cells, and will usually have a power output of between 400 watts and 450 watts. These are less often used for rooftop solar because they are difficult to handle on a roof; they are more commonly used for utility-scale solar farms.
Modern solar panels are made from silicon solar cells, which are either monocrystalline or polycrystalline (sometimes called multicrystalline) silicon solar cells.
Both are similar in terms of energy output, although panel efficiency is typically slightly higher in monocrystalline solar panels.
There’s also a third, less common type of solar module: amorphous solar panels. They are cheaper, but also produce much less power.
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 as they’re being constructed. The rods are sliced into nearly translucent wafers and formed into cells.
These panels are composed of multiple polycrystalline cells. They're slightly less efficient, but more affordable. The cells are processed differently, giving them the appearance of shattered glass. This product is also cut into very thin slices.
The cells are not crystals, but rather 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; otherwise they will not produce enough energy. The real benefit to creating amorphous solar panels is being able to form the material into long sheets that can be applied like roofing materials on south-facing roofs or other surfaces.
When we measure a solar panel’s output over time, we use the unit kilowatt-hour (kWh). One kilowatt-hour is equivalent to 1,000 watts (1 kW) of continuous power production over one hour.
Here’s how much solar power output you can expect from different sized solar panels, and how many of them you would need to build a typical 6 kW system:
|Rated output||Average monthly output*||Average yearly output||# panels for 6kW system||Example panel|
|350 W||42.6 kWh||511.3 kWh||18||Silfab Solar SLG|
|375 W||45.6 kWh||547.9 kWh||16||LG Neon R|
|400 W||48.7 kWh||584.4 kWh||15||SunPower Maxeon 3|
The above table is useful in helping you get an idea of how many solar panels you need to reach a desired power output. It allows us to answer the following questions:
A 400-watt solar panel will produce, on average, 1.6 kWh of electricity over a day, and 48.7kWh of electricity per month.
To produce 1,000 kWh in a single month, you would need 21 solar panels rated 400-watts each.
Solar power ratings are based on how much power they produce in ideal sunlight and temperature conditions (AKA 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, including:
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.
There’s no way to increase the solar panel output and efficiency a solar panel was designed to achieve.
What you can do is make sure that the solar panels are performing as efficiently as possible; this is achieved by performing routine cleaning. Dust, debris, and snow can lower the efficiency of the panels, so you’ll want to keep them clean.
Calculating the number of solar panels needed to power your home can easily be done online using our solar panel calculator. The calculator will take into account:
All of these factors influence how much solar power you need to maximize your savings where you live.
The calculator will then provide an estimate for all the key solar information you need:
The next step is to talk to local installers. They can conduct a detailed assessment of your roof and provide an actual quote and timeline for the installation of a complete solar panel system for your home. The calculator makes this process easy by allowing you to choose how many solar installers you would like to receive quotes from.