If you are planning for a solar installation, you must consider the energy-efficient factors that affect the performance of your solar panel system.

Firstly, solar panel efficiency is the rate at which your solar panel absorbs sunlight and converts them into electricity through the photovoltaic cells. When efficiency is higher, you will generate electricity at a higher rate. In general, most solar panels have an average cell efficiency of 15% to 20%. Anything above 20% is a great value. Secondly, solar panels are rated based on how much watts of energy they generate. For instance, consider a 380 watts solar panel installed on your roof, where you receive 5 hours of direct sunlight. The calculation goes like 5 hours multiplied by 380 watts is 1,900 watts which is roughly about 2.0 kWh per day. So, you generate roughly around 720 kWh of solar energy per panel for a year.

However, the actual efficiency and output of a solar power system vary depending on several factors that affect the overall performance of a solar panel system. Hence, you should consider the following factors while calculating the solar power for your property.

Inverter Efficiency

Inverters convert the DC current from the solar panel to the AC current to attend to the needs of your home appliances. Even though inverters have a higher efficiency rate, they are not 100% efficient. As a result, inverters typically contribute to an 8% loss in the total efficiency of the solar panel.

Battery Efficiency

Your battery will not provide maximum efficiency if you have a hybrid inverter system. Usually, in a hybrid system, the battery tends to operate at an efficiency that is 8% lesser than the rated wattage. So, it contributes to an 8% loss in the performance.

Manufacturer’s Tolerance

A manufacturer’s tolerance is the power tolerance of a solar system. Usually, the output power and the efficiency of solar power systems are calculated in laboratories under the Standard Test Condition (STC). There will be some change in efficiency from the original STC, and that range is power tolerance. Most solar panels have a power tolerance of +/- 5%, and it can be lower or higher depending upon the manufacturer.

DC and AC Cable Loss

Resistance loss in the DC and AC cables also affects the performance of solar panels. The voltage drops between the solar panel and the inverter accounts for a 1 to 2% loss. Similarly, the inverter and the electrical switchboard also experience some voltage drop, affecting the efficiency.

Temperature Derating

Solar panels work best at lower temperatures, whereas heat affects the performance of solar panels significantly. Every solar panel has a temperature coefficient beyond which when the solar panel gets hot, there will be a severe drop in the output voltage. In addition, the type of installation and ambient temperature also affect the efficiency. For instance, solar panels fixed parallel to the roofs may experience a temperature of 35℃, which consistently affects the efficiency.


The build-up of grime and dust also affects the efficiency of your solar power system. They may account for a 5% loss in solar panel efficiency. They may also vary depending upon your location and the panels you use. However, regular maintenance can prevent this loss.

Angles and Placement

The angle of inclination and the orientation of your solar panel also affect solar energy efficiency. Your solar panels must be placed at an optimum angle or tilt to produce maximum solar energy. Sometimes shading and other climatic factors such as clouds and rain also affect efficiency.


For more information contact the local team of solar installers at Always Energy. We offer solar installation services in Port Macquarie, Coffs Harbour, Newcastle, and the surrounding areas of NSW.