The typical solar panel operates between 250 to 400 watts and produces approximately 1.5 kilowatt-hours (kWh) of electricity daily. Many households are capable of fulfilling their energy requirements with just 20 solar panels, which usually have a power capacity ranging from six to eight kilowatts (kW).
The wattage of a solar panel is measured in a controlled environment, but its real power output fluctuates once it’s in place. The precise energy output of your system varies based on the kind of photovoltaic (PV) solar panels you choose and environmental elements such as sunlight and the surrounding temperature. Continue reading to discover the elements that influence its efficiency and strategies to enhance your solar power production.
How Is Solar Panel Power Production Measured?
The wattage of a solar panel measures how much energy it produces under standard testing conditions. While solar system size is measured in kilowatts, the amount of electricity a solar array generates is measured in kilowatt-hours.
All manufacturers use the same Standard Test Conditions (STC) to determine the nameplate wattage of a PV module:
- The panel is exposed to an irradiance or light energy of 1,000 W per square meter.
- Solar cell temperature is 25°C (77°F) at the time of testing.
- The light spectrum used during the test represents sunlight crossing the atmosphere at an angle of 48.19°. This is known as the “air mass 1.5 spectra” or AM1.5.
The output measured under laboratory conditions determines the rated wattage of a solar panel. This testing also dictates the solar panel efficiency rating. For example, if a PV module generates 220 W per square meter, it is 22% efficient.
As of June 2023, SunPower and Canadian Solar produce the most efficient solar panels in the industry — both companies have reached 22.8% efficiency. However, many other brands make solar panels with an efficiency of over 20%.
Solar panels are manufactured in standard sizes, and wattage increases with size. Smaller, 60-cell panels are common in residential installations, while 72-cell panels are normally used in commercial and industrial installations. You can find other sizes, but 60-cell and 72-cell panels are the most common.
Factors Affecting Solar Panel Power Capacity
The wattage listed on solar panel nameplates is calculated under perfect circumstances that don’t accurately represent how they perform in actual use. For instance, a panel rated at 360 W might actually work more like a 300 W one when placed on a roof facing typical sunlight conditions.
Here are a few elements that influence how much power a solar panel can generate.
1.Amount of Sunlight Exposure
Solar panels produce more power when they receive more hours of direct sunlight. If you were to compare PV systems of equal size, you’d anticipate greater efficiency in sunnier regions such as California. The World Bank Global Solar Atlas can provide an estimate of the number of hours of sunlight your area receives.
2.Ambient Temperature
More sunlight boosts the efficiency of solar panel systems, but soaring air temperatures can negatively impact them. Elevated temperatures can cause a short-term decline in the power generated by PV cells when turning solar energy into electricity.
Solar panels have a specific temperature coefficient that indicates the rate at which their cells’ power output decreases as the panel temperature increases. Typically, most solar panels exhibit a temperature coefficient of approximately -0.3% to -0.5% per °C. Consequently, a 10°C increase in temperature can result in a power output drop of about 3% to 5%.
3.Solar Battery and Inverter Efficiency
A solar panel setup also includes parts like inverters and batteries. An inverter is essential because it changes the direct current (DC) power from the solar panels into the alternating current (AC) that is needed for household devices. On the other hand, batteries are not required for systems that are connected to the power grid, but they are essential for standalone systems.
These components do not use all of the power your setup produces because they are not perfect, but you can locate inverters and battery setups with an efficiency of more than 95%. Even though this is a slight inefficiency, it’s something to think about when putting together a solar energy system.
Estimating the Potential Power Output of Solar Panels
The amount of power a solar array can generate depends on sunshine and weather conditions. To determine a system’s exact power output at any given time, you must measure it directly. But you can use the Global Solar Atlas to estimate how much energy your system will generate annually:
- Using the Global Solar Atlas, click on your location and look for a value called specific photovoltaic power output or PVOUT.
- This value estimates the annual productivity of solar panels in your location, measured in kilowatt-hours generated per kilowatt of peak capacity (kWh/kWp).
- For example, if the Atlas shows a PVOUT value of 1,500 kWh/kWp and you have an 8 kW system, you can expect to generate 12,000 kWh of electricity per year.
- Say you have an electricity tariff of 16 cents per kWh, you could save $1,920 in annual electricity bills.
- To determine the energy production of each panel, divide the total output by the number of panels. For example, if you have an 8 kW system with 20 panels that generate 12,000 kW total, each panel should generate 600 kWh of energy per year.
Power Output by Solar Panel Type
The primary element that influences how much power a panel can produce is the kind of solar cell it has: monocrystalline (the most effective), polycrystalline (a bit less effective), or thin-film (the least effective). The table below outlines the average power generation you can anticipate when looking at different solar panel types.
| Solar Panel Type | Typical Power Rating* |
|---|---|
| Monocrystalline | 320 W–380 W |
| Polycrystalline | 250 W–300 W |
| Thin-film | Less than 200 W |
Clearly, monocrystalline panels, known for their high efficiency, produce more watts than their thin-film and polycrystalline counterparts. Homeowners who have less space on their property can opt for monocrystalline panels to reach the maximum electricity yield.
Maximizing Solar Panel Power Generation
Solar panels have a rated wattage and efficiency, but their actual performance depends on many external factors. You can achieve higher efficiency by following these recommendations:
- Install your solar panels in an unshaded area.
- Clean your solar panels regularly to prevent dust and dirt from accumulating and blocking sunlight.
- Monitor the daily electricity output of your solar panel system. Many inverters have a built-in monitoring app you can install on your smartphone. Contact your solar installer if you notice any dips in system performance.
We recommend a professional installation if you plan to go solar. Solar panels that are not wired properly can suffer from low productivity or even permanent damage. Incorrectly installing your system can also void your manufacturer’s warranty. The best solar companies ensure proper solar panel installation and help you troubleshoot any issues over time.
Conclusion
The typical residential solar panel operates between 250 to 400 watts and produces around 1.5 kWh of power every day. Producers rely on certain controlled lab conditions to set the solar panel’s wattage, meaning the real power output may differ due to variables like the amount of sunlight, temperatures, and energy dissipation among other parts of the system. To increase your panel’s output, it’s recommended to use the most efficient monocrystalline panels, choose a professional to set them up, and ensure your panels remain clean and clear of any obstructions that might hinder the flow of sunlight.
The solar energy provider can determine the most suitable panel size for your property considering your daily energy use, power requirements, and the environmental conditions of your location. Since tests are conducted under uniform conditions, it’s easy to compare the power generation capabilities of panels when looking for a new set.
Additionally, providers use the specified wattages of the panels to determine the best configuration for the solar power system and to forecast the amount of electricity that will be generated.
