What is the power output of a solar panel?

Most solar panels in 2023 produce between 250 and 400 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 all refer to a solar panel's wattage, capacity, and power output.

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 watts (W) units 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 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.

Before calculating the amount of energy a solar panel can produce, one must understand the key factors determining 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 simplify things, 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 watts. On the other hand, 72-cell solar panels are larger because they have an extra row of cells, and their average output is between 350 to 400 watts. 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 directly impact the rated power of a solar panel. In the real world, there are a few more things that affect how much energy a panel will produce:

Shading will lead to lower production. Solar panel wattage ratings do not consider a panel's lowered output 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 toward the sun. In practice, roof planes are rarely perfectly angled for maximum production.

Hours of sunlight refer to the amount of time per day (or year) your panels are exposed to sunlight. The more hours in the sun, the higher your output will be.

Knowing how much energy a single solar panel produces is good, but 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 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 daily. And for one final conversion, if we multiply 43.5 by 365 days 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, check out our blog here, where we look at average sunlight per year by location.

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.

With so many solar panel manufacturers, panel output varies significantly between brands and products. In 2022, these are the top six solar panel brands in the U.S. ranked by their maximum power output panel:

1. First Solar (460 W)

2. LONGi (455 W)

3. REC (450 W)

4. SunPower (435 W)

5. Q CELLS (430 W)

6. Solaria (430 W)

The table below shows the 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

Power output is a crucial 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 grid-tied systems, 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 use battery storage, it's an essential 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 alone 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 higher efficiency or technological superiority.

For example, if two solar panels have 15 percent efficiency ratings, but one has a power output rating of 250 watts, and the other is rated at 300 watts, 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 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 comprise 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 sun each location gets annually.

The effect materials have on output

Solar panels can be made from either monocrystalline or polycrystalline cells – monocrystalline cells are more efficient and can generate more electricity than polycrystalline cells. In contrast, 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. Still, it's also dependent on other factors, such as panel efficiency and temperature sensitivity, the degree of shading that the system experiences, and the tilt angle and azimuth of the roof on which it's installed. As a general rule of thumb, 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 comparing your savings from solar panels with various power output ratings easy.

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 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 roughly 1.2kW to  2.5kW per day. Solar panel output and the available sunlight 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 daily.

How much energy do solar panels produce per hour?

The average solar panel produces 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. 

If you're in the early stage of shopping for solar and would 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.