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Solar Panel Capacity: A Full Guide to Choosing Solar Panels

solar panel capacity

Alex Richards |

Solar panel capacity refers to the maximum power output of a solar panel and is typically measured in watts (W).

Understanding solar panel capacity is critical when determining how much energy a solar system can generate to power your home or business. Moreover, choosing solar panels of adequate capacity is the key to optimizing your energy output.

In this article, we’ll explain what solar panel capacity is to help you choose the best solar panel system for your needs. Let’s begin!

What is Solar Panel Capacity?

The capacity of a solar panel describes the maximum power that the solar panel can produce under standard test conditions (STC). Solar panel capacity is measured in watts (W).

Standard test conditions in which solar panel capacity is estimated refer to the conditions of optimal sunlight with a temperature of 25°C, and watts are measured per square meter of sunlight with no obstructions.

Understanding how solar panels work, as well as their capacity, is important because it directly correlates with solar energy output. So, if you, for example, choose a solar panel of 250W capacity, it means that in ideal conditions it will produce 250 watts of energy per hour.

Additionally, bear in mind that conditions are never optimal in the real world, so the energy output will vary accordingly.

Nevertheless, choosing solar panels of adequate capacity is vital for ensuring the efficiency and cost-effectiveness of your solar power system. Given the extensive selection of solar panels with varying capacities, consulting with the knowledgeable professionals at Potable Sun can help you narrow down the array of solar kits that best align with your energy requirements.

3 Factors to Consider with Regard to Solar Panel Capacity

group of solar panels in a field

Let’s see three solar panel capacity factors that affect its efficiency and output to understand the role their capacity plays in the solar power system:

#1. Efficiency of Solar Cells

The efficiency of solar cells is the key to solar panel capacity and depends on the type of solar panel that you choose. Monocrystalline solar panels are the most powerful ones because they have solar cells of higher efficiency that can generate more power per square meter than other solar panel types.

Moreover, the latest models of solar panels come with passivated emitter rear cell technology (PERC), which also significantly contributes to the improvement of the solar panel capacity by reducing the loss of electrons.

#2. Panel Size and Type

Higher-wattage panels are a good choice for those looking to maximize energy output with fewer panels, especially in installations with limited space. However, for those with sufficient space or lower energy requirements, medium-power panels are the most cost-effective solution.

Another important factor that affects the capacity of solar panels is solar panel efficiency. Higher-efficiency solar panels can produce more energy while taking up less space, which can compensate for slightly lower power in certain cases.

Monocrystalline solar panels have the highest efficiency rate compared to polycrystalline or thin film solar panels.

It is important to bear in mind that high-efficiency solar panels typically have a capacity of 350-400W, but their performance can match or outperform panels with higher wattages but lower efficiencies.

#3. Sunlight Intensity and Duration

Areas with less direct sunlight can benefit from higher-wattage panels to compensate for the lack of peak hours of sunlight. If you live in a location with high sun exposure, you may not need the highest capacity panels, as even mid-range panels can generate significant power in those conditions.

Conversely, if you’re in a region with frequent clouds or shorter daylight hours, higher-wattage panels will help ensure consistent energy production.

In addition, it is important to install panels at optimal angles to ensure maximum sunlight exposure and maximize solar power usage. Solar tracking systems can also help boost the overall solar system capacity.

How to Calculate Solar Panel Output, Considering Its Capacity

If you want to know how much energy your solar power system can generate, you will need to learn how to calculate solar panel capacity. So, below, we’ve described the most popular methods and metrics for solar panel capacity calculation.

Solar Panel Output Per Day

Here’s how to calculate solar panel output per day in two easy steps:

Determine the panel’s wattage (which is usually stated in documents that come with the panel, on the panel packaging, or in other visible places).

  1. Take the average sunlight hours in your area into account and multiply the solar panel’s wattage by those hours.

The formula would look like this:

Panel Wattage x Sunlight Hours = Daily Solar Panel Output

So, for example, if you have a panel of 300W capacity and live in an area with five sunlight hours on average, this is how you would calculate the output: 300W x 5h = 1500Wh.

Solar Panel Output Per Square Meter

When we talk about solar panel capacity per square meter, we’re actually thinking about solar panel output per square meter. The key factors for calculating solar panel output per square meter are the solar panel’s capacity and size.

The formula for this calculation looks like this:

Panel Efficiency x Solar Irradiance (W/m2) = Output Per Square Meter (W/m2)

So, if, for example, you have a solar panel of 20% efficiency and 1000 W/m2 of sunlight, the power production will be 200 W per square meter.

Multiple Panels System Capacity

Since you’re surely going to need more than one solar panel, and not all of them have to be of the same capacity, it is recommended to calculate the capacity of your entire solar system. This is done by multiplying the number of panels by the panel wattage.

Here’s the formula:

Number of Panels x Panel Wattage = Total Capacity

So, for example, if you have 10 panels of 250W, the overall capacity of your panel system will be 2500W.

How Many Solar Panels Does an Average American Household Need?

solar panel capacity

An average American household typically needs around 20 to 25 solar panels to cover its energy needs. Nevertheless, you should never use this number as an indicator of how many panels you need, as the optimal number of panels for your household depends on solar panel capacities per panel and many other factors that you need to consider carefully.

How To Choose the Optimal Solar Panel Capacity and Number for Your Needs

Higher-capacity panels are a good choice for those looking to maximize energy output with fewer panels, especially in installations with limited space. However, for those with enough space or lower energy requirements, medium-power panels are the most cost-effective solution.

So, let’s go through all the key factors that need to be considered when choosing solar panel capacity:

#1. Energy Requirements

The first step is to determine the energy needs of your home or business. You can calculate this by looking at your electricity bills, which show your monthly and annual energy consumption in kilowatt-hours (kWh).

For example, if you use 10,000kWh per year, divide this by the maximum number of hours of sunshine your location receives per year. If your area receives 1,500 hours of sunlight per year, you will need about 6.67 kW of solar panel capacity.

To achieve this capacity, you can choose a combination of solar panels of the appropriate power. For example, when using 400W panels, you will need approximately 17 panels.

#2. Available Roof Space

The size of your roof or the area where the panels will be installed determines how many panels you can install. Higher-wattage panels (such as 500W or 600W) are usually larger but produce more power, meaning you may need fewer of them compared to lower-wattage options.

If your roof space is limited, it is better to opt for high-power panels to maximize energy production in a smaller space.

#3. Budget and Cost-Efficiency

As we have already mentioned, higher-wattage panels are usually more expensive but offer higher efficiency per panel, meaning fewer panels need to be installed. This can reduce labor and installation costs, as well as wiring and mounting system costs. However, lower-wattage panels may be a better option for budget-conscious consumers, especially if space is not an issue.

Comparing cost per watt is a useful metric to ensure you get the most energy for your investment.

#4. Efficiency of Solar Panels

Solar panel's efficiency plays a significant role in how much energy they can produce from the available sunlight. Higher-efficiency panels can produce more energy with a smaller area, which can make up for slightly lower capacity in certain cases.

Solar panels with a high-efficiency rating can be as powerful as or more powerful than panels with a lower efficiency rating, even though their wattage ratings are lower.

The point is that if you have limited space but high energy requirements, choosing a high-efficiency panel, even with a slightly lower capacity, could be a smart move.

#5. Sunlight Conditions

If you live in places with abundant sunshine, you will need fewer panels to produce the same energy as in places with less sunlight. So, your geographic location and sunlight hours are two of the most important factors to consider.

#6. Energy Independence Goals

If you want to go completely off-grid, you might need a higher number of solar panels or panels of higher efficiency and wattage. Adding energy storage, such as solar batteries, is also a great option in this case and may influence the total number and wattage of panels that you might need.

Battery storage and solar capacity are connected in the sense that the overall solar power system efficiency is increased when you use battery storage.

How to Maximize Solar Panel Capacity and Solar Panel Efficiency Tips

While solar panel capacity can’t be maximized per se, you can maximize solar power usage and the panel's output and efficiency. With that in mind, here are some crucial factors affecting solar panel performance and key strategies that can help you take maximum advantage of your solar power system:

  • Regular maintenance and cleaning. By cleaning the panels regularly and removing dust and debris, you're maximizing their exposure to sunlight, ensuring optimal conditions for their operation.
  • Optimize installation angle. By adjusting the tilt of the panels to maximize sunlight exposure depending on seasonal changes, you’re contributing to solar panel efficiency.
  • Upgrade solar system components. Installing microinverters or power optimizers can improve the panel’s power output, as can using the latest models of solar generators and other solar system components.
  • Use solar tracking systems. By installing single-axis or dual-axis solar trackers, you can track the sun's movements, thus maximizing the solar panels’ exposure to sunlight and improving the system’s efficiency.
  • Reduce shading effects. Trim surrounding vegetation to reduce shading on the panels.
  • Monitor system performance. Use monitoring tools to regularly check system performance and identify problems. 
  • Manage temperature. Ensure adequate spacing between panels for better airflow and lower temperatures.
  • Upgrade wiring and connections. Check and secure electrical connections, using thicker wires if necessary to reduce energy loss.

Ready to Harness the Solar Energy?

Take your energy independence to the next level with Portable Sun’s products! We’ve got everything you need to optimize your solar power system, and our experts will be happy to help you make all the calculations and design the solar configuration that perfectly meets your energy needs.

Explore our solar products offer here!

Final Thoughts

After reading this article, you should be able to understand the difference between solar panel capacity and solar panel efficiency and why they are important.

If you’re interested in solar energy and installing a solar power system, the best thing to do is to consult solar energy experts about all your concerns. At Portable Sun, you can always get all the information about solar panel capacity for your home, as well as other answers to questions related to your solar panel system.

Solar Panel Capacity FAQ

#1. How much energy do solar panels produce per day?

The energy solar panels produce per day depends on their capacity and sunlight exposure. For example, a solar panel of 300W exposed to direct sunlight for 5 hours will produce 1.5 kWh per day.

#2. How do I check that my solar panels are working efficiently?

The best way to check if your solar panels are working efficiently is to use a monitoring app and compare real-time production with expected values based on solar panel capacity and sunlight hours. Regular solar panel maintenance can also help in ensuring optimal performance.

#3. How big is a 1 kW solar panel?

Typically, a 1 kW solar panel takes about 5-6 m2 of space. However, the size of the panel depends on its wattage and efficiency. Higher-efficiency panels usually require less space.

#4. What solar panels have the highest capacity?

Monocrystalline solar panels, like those included in the Portable Sun’s offer, usually have higher capacity than other panel types. High-capacity solar panels maximize energy production while reducing the number of panels needed for your system.

Disclaimer: The content on Portable Sun is for informational purposes only. Electrical work can be dangerous—always consult a qualified professional. We are not liable for any injuries, damages, or losses from installation or use. Always follow local regulations and safety guidelines when handling electrical components.