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

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

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).

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…