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What is the output of a solar panel?

Most solar panels on the market in 2023 produce between 250 and 450 watts of power. You might come across these solar panel output numbers from your solar installation quote, which will typically include “245W”, “300W”, or “345W” next to the name of the panel. They are all referring to a solar panel’s wattage, capacity, and power output.

Key takeaways about solar panel output

  1. Currently, most solar panels on today’s market usually produce between 250 and 400 Watts of power — your actual output will depend on factors like shading, orientation, and sun hours.

  2. With a 30-panel system, you’ll be producing more than enough electricity per year to match all of your electricity usage, and maybe more!

  3. You can freely compare solar quotes on the EnergySage Marketplace to see how different wattage panels will affect your unique system

What’s in this article?

What are solar panel output ratings?

All solar panels are rated by the amount of DC (direct current) power they produce under standard test conditions. Solar panel output is expressed in units of watts (W), and it represents the panel’s theoretical power production under ideal sunlight and temperature conditions (25°C). It indicates the expected energy production, or capacity, of one individual solar panel. Solar panel output over a given time period is expressed in kilowatt-hours (kWh). Once you understand these vital solar panel output ratings, you can calculate how much output your solar panel system can produce in a day, month, and even year.

How to calculate how much energy a solar panel produces

All solar panels are rated by the amount of DC (direct current) power they produce under standard test conditions. Solar panel output is expressed in units of watts (W) and represents the panel’s theoretical power production under ideal sunlight and temperature conditions. Wattage is calculated by multiplying volts x amps where volts represent the amount of force of the electricity and amperes (amps) refer to the aggregate amount of energy used.

Most home solar panels on the market today have power output ratings ranging from 250 to 400 watts, with higher power ratings generally considered preferable to lower power ratings. Pricing in solar is typically measured in dollars per watt ($/W), and your total solar panel wattage plays a significant part in the overall cost of your solar system.

For example, if you are getting 5 hours of direct sunlight per day in a sunny state like California you can calculate your solar panel output this way: 5 hours x 290 watts (an example wattage of a premium solar panel) = 1,450 watts-hours, or roughly 1.5 kilowatt-hours (kWh). Thus, the output for each solar panel in your array would produce around 500-550 kWh of energy per year.

What factors determine solar panel output?

Before calculating the amount of energy a solar panel can produce, it’s important to understand the two key factors that determine its power output: cell efficiency and solar panel size.

Let’s assess each factor separately to understand them a bit better.

Solar panel efficiency

Of all the metrics to look at when shopping for solar panels, efficiency is one of the most important. The higher a panel’s efficiency is, the more power it can produce. Today, most silicon-based solar cells can convert between 18 and 22 percent of the sunlight that hits them into usable solar energy, which has led to panels exceeding 400 watts of power. Higher efficiency = more energy, so high-efficiency solar panels generally will produce more electricity for your home. As of 2022, the National Renewable Energy Laboratory (NREL) developed the most efficient solar cell to date at 39.5 percent efficiency.

Number of solar cells and solar panel size

To make things easy, we can divide solar panels into two size groups: 60-cell solar panels and 72-cell solar panels. Usually, 60-cell solar panels are about 5.4 feet tall by 3.25 feet wide and have an output of about 270 to 300 W. On the other hand, 72-cell solar panels are larger because they have an extra row of cells, and their average output is somewhere between 350 to 400 W. Although they have roughly the same width as 60-cell panels, 72-cell panels have an average height of 6.5 feet. 72-cell panels are usually used on larger buildings and in commercial solar projects, not on residential homes. 

Environmental factors: shading, orientation, and hours of sunlight

Solar panel efficiency and the number/size of solar cells in a solar panel are factors that directly impact the rated power of a solar panel. In the real world, there are a few more things that impact how much power a panel will actually produce:

Shading of your solar panels will lead to lower production. Solar panel wattage ratings do not take into account the lowered output of a panel when there’s shade blocking the sun.

Orientation of your solar panels also impacts production in a way that a panel’s output rating doesn’t capture. Ideally, your panels will be angled directly towards the sun. In practice, roof planes are almost never perfectly angled for maximum production.

Hours of sunlight simply refer to the amount of time per day (or year) that your panels are exposed to sunlight. The more hours in the sun, the higher your actual output will be. The amount of sunlight your panels receive not only depends on your location in the country but also the time of year. States like Massachusetts may not receive as much sunlight year-round whereas other states such as California and Florida have a significant amount of sunlight for the whole year.

What can you power with a single solar panel?

In the example above, the solar panel is producing 1.5 kWh per day, which is about 45 kWh per month. That’s enough energy to power some small appliances without too much issue, but if you want to cover the energy used by your property’s climate control systems or large cooking appliances, you’ll need more solar panels. Check out our article on how many solar panels you need for your home to better understand how much solar energy your unique property needs.

How much energy will an entire solar panel system produce?

Knowing how much energy a single solar panel produces is all well and good, but more importantly, how much solar power can your roof generate? Let’s do the math below:

Take our example above, where you’re getting an average of five hours of direct sunlight per day (an average amount of sunlight for most areas of California) and using solar panels rated at 290 W. Let’s say you install 30 of those premium solar panels on your roof–that nets you an 8,700 watt, or 8.7 kW solar panel system, near the average system size purchased on the EnergySage Marketplace. Multiply the five direct sunlight hours we estimated above by 8.7 kW, and we get approximately 43.5 kWh of electricity produced per day. And for one final conversion, if we multiply 43.5 by 365 days in a year, we get approximately 15,800 kWh of electricity produced in a full calendar year from a rooftop array of 30 premium, 290 W solar panels. Considering that the yearly average for electrical power is around 10,600 kWh in the U.S., that’s probably more than enough to power your home on solar.

This estimate is likely on the high end for most solar shoppers, and likely because of our estimate for the amount of sunlight the system will get (known as sun hours). To learn more about average sun hours,  you can learn more from our blog post where we take a look at average sunlight per year by location.

Solar panel output and cost

The output of a solar panel has a significant impact on its cost. This cost can vary based on where you live and what your needs are, but with data from the EnergySage Marketplace, we can get an idea of how much it could cost on average for 3kW,4kW, 5kW, 6kW, 7kW, 8 kW, and 10kW solar systems. To find out how much this could be for you, simply find the average cost per watt in your area and multiply that by the output of the solar panel you have in mind.

What are the best solar panels by output?

With so many solar panel manufacturers on the EnergySage Marketplace, panel output varies significantly between brands and products.With so many solar panel manufacturers on the EnergySage Marketplace, panel output varies significantly between brands and products. RankBrandEfficiencyPower output 1SunPower22.8%440W 2Canadian Solar22.8%430W 3REC22.3%430W 4Panasonic22.2%410W

The table below presents a view of power output from many manufacturers supplying solar panels to the U.S. market. Because panel manufacturers often produce more than one line of solar panel models, the power output of most companies has a significant range. The table below lists the solar panels’ minimum, maximum, and average power outputs within each manufacturer’s portfolio.

Electricity output (in Watts) of solar panel manufacturers Solar Panel Manufacturer Minimum Maximum Average Amerisolar240330285 Astronergy350370360 Axitec250385302 BenQ Solar (AUO)250295277 Boviet Solar320340330 Canadian Solar225410320 CentroSolar250320278 CertainTeed Solar70400308 ET Solar255370306 First Solar420460440 GCL310330320 Grape Solar160285237 Green Brilliance230300266 Hansol250360304 Hanwha365385375 Heliene250370306 JA Solar260410329 JinkoSolar315410367 Kyocera260330295 LG315415365 LONGi305455387 Mission Solar Energy300390334 Mitsubishi Electric270280275 Neo Solar Power310330320 Panasonic320370340 Peimar310310310 Peimar Group270330301 Phono Solar260350294 QCELLS285430358 REC275450347 RECOM265370308 Recom Solar310350330 ReneSola245320277 Renogy Solar250300268 RGS Energy556058 Risen270390329 S-Energy255385334 Seraphim255340294 Silfab300390335 Solaria350430375 Solartech Universal310325318 SunPower320435355 SunSpark Technology310310310 Talesun275415365 Talesun Solar Co.400400400 Trina265415337 Trina Solar Energy260320288 Upsolar270365311 Vikram Solar320340330 Winaico325340332

Why does solar panel output matter?

Power output is an important metric for your home or commercial solar panel system. When you buy or install a solar photovoltaic (PV) energy system, the price you pay is typically based on the solar panel output of your system (expressed in watts or kilowatts).

Solar panel wattage represents a solar panel’s theoretical power production under ideal sunlight and temperature conditions. Wattage is calculated by multiplying volts x amps where volts represent the amount of force of the electricity and amperes (amps) refer to the aggregate amount of energy used. For systems that are grid-tied, open-circuit voltage and the voltage of your system may not be as significant of an issue. For those that are off-grid or wish to utilize battery storage, however, it’s an important part of your PV system. The financial savings you derive from your solar system result from the electric energy it generates over time (expressed in kilowatt-hours).

How do size and quantity impact output?

Power output on its own is not a complete indicator of a panel’s quality and performance characteristics. Some panels’ high power output rating is due to their larger physical size rather than their higher efficiency or technological superiority.

For example, if two solar panels both have 15 percent efficiency ratings, but one has a power output rating of 250 watts, and the other is rated at 300 watts, it means that the 300-watt panel is about 20 percent physically larger than the 250-watt panel. That’s why EnergySage and other industry experts view panel efficiency as being a more indicative criterion of solar panel performance strength than solar capacity alone.

In practical terms, a solar panel system with a total rated capacity of 5kW (kilowatts) could be made up of either 20 250-Watt panels or 16 300-Watt panels. Both systems will generate the same amount of power in the same geographic location. Though a 5kW system may produce 6,000 kilowatt-hours (kWh) of electricity every year in Boston, that same system will produce 8,000 kWh yearly in Los Angeles because of the amount of sun each location gets each year.

Solar panels can be made from either monocrystalline or polycrystalline cells – monocrystalline cells are more efficient and able to generate more electricity than polycrystalline cells, while polycrystalline solar panels are much more affordable. NREL also has a team of researchers working to improve solar cell technology to increase efficiency and lower manufacturing costs.

The electricity generated by a solar PV system is governed by its rated power output, but it’s also dependent on other factors such as panel efficiency and temperature sensitivity, as well as the degree of shading that the system experiences and the direction and angle of the solar panel.

Panel efficiency: Solar panel efficiency is the percentage of incoming sunlight a single solar panel can convert into usable electricity. For example, a high-efficiency solar panel with a 20% efficiency rating will convert 20% of the sun’s energy to solar energy. If two solar panels receive an equal amount of sunlight for the same duration, the panel with a higher efficiency rating will produce more output than the panel with a lower efficiency rating.

Temperature sensitivity: Homeowners considering solar often wonder, “can solar panels overheat?” Similar to any other electronic equipment, solar panel performance declines as the system gets hotter. Thus, increased temperatures will always lead to decreased output for PV cells. This loss is quantified in a “temperature coefficient” by panel manufacturers, which varies from model to model.

Degree of shading: As mentioned above, shade on your solar panels will reduce output. Shade can come from several sources, including trees, clouds, other solar panels, and even your roof. Depending on the sun’s angle and the time of day, different parts of your roof (like a chimney or dormer) can block sunlight to certain panels. Solar panels will still work in shaded areas. However, they will operate at a reduced capacity due to lower sunlight exposure. Though the numbers will vary depending on how much shade the panels are facing, the general rule with shade is that solar panels will produce about half as much energy as they would with direct sunlight.

Solar panel direction: The direction that your roof faces is one of the primary factors in determining how much sunlight your solar panels will receive throughout the day. For those north of the Equator, the best direction for solar panels is south, while homes in the southern hemisphere would position solar panels on roofs with a northern-facing orientation. Solar panels do not need to be south facing, but by positioning them according to true south and the azimuth angle–the angle of the sun in relation to true north and true south–you’ll be able to get the most output.

Solar panel angle: The angle, or vertical tilt of your solar panel system, greatly affects the performance of your solar panels. In order to collect solar power energy more efficiently, you should angle your solar panels to face as close to the sun as possible. Photovoltaics produce power when the angle at which the sun’s rays hit the panel surface (the “angle of incidence”) is small, or when light strikes the panel as close to perpendicular as possible. Therefore, the best angle for your solar panels is the one that allows the panels to get the most direct, perpendicular light. As a general rule, it makes prudent financial sense to install a solar system with as much power output as you can afford (or that your roof will accommodate). That will ensure you maximize your savings and speed up the payback period of your solar energy system.

Find out more about average prices for solar across the country for 3kW,4kW, 5kW, 6kW, 7kW, 8 kW, and 10kW solar systems. The EnergySage Marketplace makes it easy for you to compare your savings from solar panels with various power output ratings.

Common questions about how much energy a solar panel produces

Because few people own just one solar panel, we talk more about the system output than individual solar panel output. Here are some of the questions we are frequently asked surrounding how much energy solar panels, and solar panel systems as a whole, generate.

How many solar panels do I need for 1000 kWh per month?

This depends on weather conditions, how much sunlight a location gets, and solar panel output. It would take about 27 solar panels to produce that much electricity in ideal conditions with the average solar panel.

How much does a 300-watt solar panel produce?

A panel of this size would produce between roughly 1.2kW to  2.5kW per day. Solar panel output and the amount of sunlight available will impact how much energy it produces.

How much power does 5kW solar produce?

If exposed to the sun at least four hours a day, a system of this size can produce up to 20kWh per day.

How much energy do solar panels produce per hour?

The average solar panel produces from 170 to 350 watts every hour, depending on the region and weather conditions. This works out to about 0.17 kWh to 0.35 kWh per solar panel. 

Explore your solar options today with EnergySage

If you’re in the early stage of shopping for solar and would just like a ballpark estimate for an installation, try our Solar Calculator, which offers upfront cost and long-term savings estimates based on your location and roof type. For those looking to get and compare quotes from local contractors today, check out the EnergySage Marketplace.

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