Solar system not producing as much as it should be

Are you wondering why your solar panel system isn’t generating the maximum power it’s rated for? You’re not alone. Many Australian homeowners and businesses face this issue and seek to understand the discrepancy between the installed capacity and actual output of their solar systems. While a solar panel system’s rated capacity provides a standard measure of its potential, several variables can affect its real-world performance.

In this article, we’ll explore the multitude of factors that can influence your solar system’s energy output, from environmental conditions and system positioning to technical aspects and even local regulations. Understanding these variables will empower you to optimise your solar investment and make the most of Australia’s abundant sunshine.

Example Calculation: Understanding Your Solar Output

To grasp why your solar system might not be generating its max output, consider a 10kW system. This system can generate 10kW per hour under ideal conditions—1,000 watts per square metre of solar irradiance, 25°C temperature, and perfect alignment with sunlight.

Assume real-world conditions:

• Current solar irradiance: 800 watts per square metre
• Temperature: 35°C
• Panels are not perfectly north-facing

Example output calculation:

• Irradiance Losses: 10kW reduced by sunlight conditions becomes 8kW (10kW x 800/1,000).
• Temperature Losses: The extra heat might reduce this to about 7.68kW (8kW x 96%).
• Orientation Losses: If your panels aren’t perfectly placed, you might end up with around 6.9kW (7.68kW x 90%).

Under these conditions, your 10kW system might actually produce around 6.9kW per hour.

Remember, conditions can change rapidly. Ten minutes later, a cloud could move or a cool breeze could lower the temperature, potentially increasing your output. Therefore, it’s useful to think of your system’s performance as a range, not a fixed number.

Factors Impacting Peak Solar Production

There are many factors that can impact solar production and cause a difference in your energy generation vs your system maximum rated output, some in your control to fix, others not. This includes:

Export Limiting
When you’re on single-phase electricity, you can only export a maximum of 5kWh of unused solar electricity back to the grid at any given time. This means your system adjusts its output to combine your home’s usage with what can be sent back to the grid, capping the total generation.

For example, if your home is using 1kWh and the export limit is 5kWh, your system will only produce 6kWh, even if its peak capacity is higher and the sun is shining enough to make 10kW. As you increase your homes energy usage to say 4kWh, with the 5kWh your system would produce 9kWh.

The export limit effectively limits your system’s peak production, especially if your household’s electricity consumption is low and you’re already exporting near the allowable limit. To decrease this impact you should either consume more of the solar energy you produce or considering investing in battery storage, allowing the system to operate closer to its peak capacity.

Current Weather vs Maximum Output Rated Weather
When it comes to understanding why your solar panels aren’t hitting their maximum output, weather is a big factor to consider. Solar panels are rated based on ideal conditions, which usually means direct sunlight at a specific intensity, often 1,000 watts per square metre. In real life, the weather varies. On cloudy or rainy days, the amount of sunlight that reaches your panels will be less than ideal, causing your system to generate less electricity than its maximum rated output.

Temperature Of Panels
Another crucial factor affecting solar panel efficiency is temperature. You might think that the hotter it is, the better your panels will perform, but that’s not the case. Solar panels actually become less efficient as they get hotter, a phenomenon known as the temperature coefficient. This means that on particularly hot days, you might notice a dip in your solar system’s energy production.

Temperature of Inverter or Battery
The temperature can also impact the efficiency of your solar system’s inverter and battery. Although these components are typically installed in a secure and suitable location, such as a garage, they may still be exposed to higher temperatures, particularly during Australia’s hot summers. High heat can reduce the efficiency of the inverter as it throttles its performance to lower heat – and the storage capacity of the battery. To mitigate this, ensuring adequate ventilation in their area is crucial. Adding a fan or improving air circulation can help maintain a cooler environment, thus preserving the optimal functionality of these key components, regardless of external temperatures.

Angle and Orientation
In Australia, solar panels often perform best when they’re north-facing. However, your roof’s layout may not allow for this ideal orientation, necessitating the placement of panels on various parts of the roof. This can mean that not all panels are optimally angled to capture sunlight throughout the entire day. Additionally, your system might be designed for balanced daily power generation.

For example, some panels might face east for morning energy production, north for midday, and west for the late afternoon. This approach aims to spread out energy production over the course of the day, rather than achieving peak output for a brief period. So, if you find that your system isn’t reaching its maximum output, it’s often a deliberate design choice to ensure more stable energy generation throughout the day.

Shading
Shading on your solar panels can significantly affect your system’s performance, often more than you might expect. Elements like nearby trees, buildings, or even seemingly minor obstructions like dirt and bird droppings can cast shadows on your panels, reducing their efficiency.

The impact of shading can be especially pronounced in systems where panels are arranged in strings, a common configuration. In such systems, the underperformance of even a single panel can reduce the output of the entire string. This domino effect can happen for a variety of reasons, including manufacturing differences between panels or having panels within the same string oriented differently. So, if you notice that your solar system isn’t generating as much power as you’d expect, it’s worth checking for shading issues that could be impacting the whole setup.

Expected & Gradual Equipment Loss
Your solar system’s output is influenced by both expected and gradual equipment loss. Expected losses, like the 3-5% inefficiency in inverter energy conversion and minor resistance in wiring, are built into the system’s design. Gradual losses occur over time, such as solar panels naturally degrading at an average rate of 0.5% in efficiency per year. While expected losses are a standard part of solar energy conversion, gradual losses can be mitigated with regular maintenance to keep your system performing optimally over the years.

So, What Should You Do?

For factors within your control like shading or export limitations, take proactive steps to address them. Eliminate shading where possible and aim to use more of the solar energy you produce during peak times.

For aspects outside of your control, such as weather, panel angle and orientation, or temperature fluctuations, it’s important to remember that your system will rarely, if ever, generate its maximum rated power.

Instead of dwelling on this, focus on other ways to maximise your investment in solar, such as considering a battery storage solution or being strategic about your energy use during peak production times.