How much energy does a solar panel produce? Solar panel output explained

Power output or wattage is an important factor to consider when comparing solar panel options. You may hear your solar installer say, “it’s a 255 Watt panel” or “the panel I am recommending is has a solar panel wattage of 300.” Or, when you are reading a quote from a solar installer, you might see numbers like 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.

Last updated on 04/07/2022

What’s in this article?

• What factors determine solar panel output?
• What brand of solar panels produces the most electricity?
• How much energy does a solar panel produce?
• How much energy will your whole system produce?
• Why does solar panel output matter?
• How many watts of energy does a solar panel produce?
• What solar panels produce the most electricity?

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 and output

Today, most silicon-based solar cells can convert about 20 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.

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 watts. 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 watts. 72-cell panels are usually used on larger buildings and in commercial solar projects, not on residential homes. 

What brand of solar panels produces the most electricity?

The average range of most solar panels available to day is 250-400 watts. Currently, SunPower’s monocrystalline solar panels produce the most electricity of all solar manufacturers. Their average efficiency is almost 21%, which is slightly better than the runner- up, LG. For homes that live in areas that may not get a full day of sun all the time, or properties with fewer square meters to work with, a more efficient solar panel may be the best option.

How much energy does a solar panel produce?

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. 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 can you power with a single solar panel?

In the example above, the solar panel is producing 1.5 kWh per day, which ends up being 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 a 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 a 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, check out our blog here, where we take a look at average sunlight per year by location.

Why does solar panel output matter? Calculating panel wattage

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) refers 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 is a result of the electric energy that it generates over time (expressed in kilowatt-hours).

What is more important -Size  quantity? Typical solar panel ratings and capacity

Power output on its own is not a complete indicator of a panel’s quality and performance characteristics. For some panels, their 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 every year in Los Angeles because of the amount of sun each location gets each year.

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 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 Solar Marketplace makes it easy for you to compare your savings from solar panels with various power output ratings.

How many watts of energy does a solar panel produce? Individual products compared

The graphic below presents a view of power output from many of the manufacturers who supply 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 minimum, maximum, and average power outputs of the solar panels within each manufacturer’s portfolio.

Electricity output (in Watts) of solar panel manufacturers

What solar panels produce the most electricity?

Solar panels usually range in wattage output from around 250 watts to 400 watts, but some panels exceed the 400 watt mark. The solar panel with the highest watt is the SunPower E-Series, a commercial solar panel line. The top panel in the E-Series comes out at a whopping 435 watts. When just looking at residential solar panel wattage, the top panel available is the SunPower A-Series AC Module – the top panel in the A-Series line boasts a wattage of 425 watts.

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 that 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.

The most 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.