Solar Panels in Winter Months

It is common to wonder if solar panels work as well in winter months particularly as photovoltaic systems rely on sunlight to generate electricity. While in winter there are less available sunlight hours, solar panels still work well to produce electricity albeit a little less than in summer months. Solar panels rely on sunlight and uv not heat to produce energy so they still work in the cooler months. There are even some benefits of using solar at this time as they operate more efficiently at lower temperatures. Understanding how solar panels work in winter is important for managing expectations and helping to optimise energy production.

How Solar Panels Produce Electricity in Cold Temperatures

Understanding the way solar panels produce electricity is crucial for explaining how they can work in winter. Solar panels produce electricity using light and not heat so solar panels can work during the daylight hours even when it is cold. Solar panels are made up of photovoltaic cells which are devices that convert light to electricity. Each panel has a series of these cells and when the sunlight hits them, a chain reaction begins to start the conversion process. Each solar cell absorbs the sunlight which is made up of small particles called photons. When these photons strike the cell, they transmit energy to the electrons within the cells, creating the electrical current. This first form of electricity generated from the solar cells is direct current (DC) which must be converted through the inverter into alternating current (AC) to be used in the home. Cold temperatures usually have no effect on the way a solar panel produces electricity as the solar cells rely on sunlight not temperature to work. In fact, colder temperatures can actually be beneficial for solar panel performance as the semiconductor materials are able to more easily capture and convert the sun’s energy into electricity. Hot, sunny conditions, on the other hand, can decrease efficiency. High temperatures above 25°C decrease energy efficiency by about 0.3% to 0.5% for every degree above this temperature.

Solar Panel Efficiency in Winter

Although solar panels do not produce as much electricity in winter, they are still efficient. Solar panel output in Australia typically drops by 20% to 50% due to shorter days and lower sunlight angles. However solar panels are still efficient and often produce 50 to 80% of their maximum potential on clear days. Even states like Tasmania that are perceived as cooler and cloudier, receive ample sunlight for power generation throughout the year. On average, Tasmania receives about five hours of sunlight per day. During the winter months, the average number of peak sunlight hours is about three to four. With five to six hours of sunlight per day, a 6.6kW solar panel system can generate 19kWh to 22kWh of power every day, which is ample for a household with four people. In winter, power generation may be reduced to 10kWh on cloudy days up to 20kWh on clear winter days.

Solar Panel Efficiency in Winter vs Summer

The below table shows each capital city in Australia comparing solar output between winter and summer. The table is based on the same system size of 6.6kW, with panels that are north facing with good tilt and no major shading.

Factors that Affect Solar Panel Efficiency in Winter

While solar panels still produce electricity in winter, efficiency is reduced compared to the summer months in all capital cities except Darwin. In winter there are factors that will decrease solar panel efficiency but also those that will increase it.

Factors that will decrease solar panel efficiency

• Shorter days and lower sun angle: In winter the days are shorter so solar panels have fewer hours to produce electricity. Less hours of sunlight mean less total energy production per day. During winter the sun is also lower in the sky which causes the sunshine to hit the solar panels at a more shallow angle. This reduces the intensity of the sunlight connecting to the panels and increases reflection loss.
• Cloud cover: Winter usually means more cloud cover and less sunny days. Clouds reduce the amount of sunlight that can strike the solar panels to generate electricity. Typically, an overcast and cloudy day may reduce solar panel output by between 10 and 25%.
• Snow, dirt and debris: Depending on the location, snow can be a factor affecting solar panel output. When snow builds up on the solar panel the sun cannot connect to the cells so efficiency is decreased. Dirt and debris from falling leaves, branches or dust has the same effect prohibiting solar panels from receiving light.

Factors that will increase solar panel efficiency

• Cold temperatures: While solar panels require sunshine to create electricity, they do not require heat as too much heat can reduce efficiency. Temperatures above 25℃ increase the electrical resistance inside the panel which reduces performances. Cold temperatures on the other hand, can help increase solar panel efficiency by reducing electrical resistance in the cells, allowing the electrons to flow more freely and creating higher voltage output.
• Albedo effect: The albedo effect is the amount of sunlight a surface can reflect. For those with bifacial solar panels, solar panel efficiency can be increased in winter by using reflective light in addition to standard direct sunlight.

If Solar is Efficient in Winter, Why is my Bill High?

There are several reasons bills might still be high even though solar panels can still produce electricity in winter. Winter days are shorter which means the sun is out for less time. Even though the cold climate can help with solar efficiency, the total amount of energy produced is reduced. This means more reliance on the grid and buying from an electricity supplier instead of creating it all with the solar system. Cloudy or overcast winter days further reduce output so that even high quality panels will produce significantly less than in the warmer months. Typically in winter, energy consumption will also increase as will power bills. Heating, electric hot water and longer lighting hours mean higher consumption which increases energy costs.

Factors like system size and winter energy tariffs can also affect bills. A small or poorly oriented solar system sometimes struggles to meet energy demands and cover peak winter expenses, while the feed in tariffs may not be able to offset winter usage. Bills become higher because the household is using more electricity than the solar system can produce.

How to Maximise Solar Panel Efficiency in Winter

To maximise solar panel efficiency during winter months there are a number of things you can do from using high efficiency panels to maintenance and using battery storage. The best ways to ensure maximum efficiency from a solar system are:

• Ensure optimal panel angle: Solar panels should be angled at the latitude angle plus 15° and face true north in the southern hemisphere. This way they will capture the most sunlight.
• Clear shading: Remove any shading from trees or other fixtures as shading dramatically reduces output.
• Shift energy usage: Change energy usage if possible by focusing on daytime usage and running high energy appliances in daylight hours.
• Consider battery storage: Battery storage is one of the best ways to maximise solar panel efficiency in winter. Even if the solar panels are efficient, shorter days and higher electricity usage can leave homeowners reliant on the grid. A solar battery allows you to store solar energy to be used when sunlight is weak or no longer there.
• Check for rebates: The government offers incents and rebates for installing solar panels or batteries. Check to see if you are eligible.
• Use high efficiency panels: High efficiency panels can help produce more energy in low light conditions.
• Clean panels: Keep panels clean and maintained to ensure they are operating at peak capacity. Make sure panels are free from dust, leaves and bird droppings so sunlight can connect to the solar cells.
• Upgrade appliances: Replace old appliances that may be using more electricity than necessary. Upgrade to energy efficient or solar compatible models.
• Monitor performance: Track and monitor solar panel performance and household consumption to identify any issues of underperforming panels, shading or faults. This will also help to use energy more efficiently in the home.

Benefits of Installing Solar Panels in Winter

If you decide to install solar panels in winter, there can be a range of benefits especially in places like Tasmania where the winters are cooler and darker. The benefits include:

• Lower demand makes it the perfect time to install: When solar panel installations are not in high demand, costs can go down and retailers can offer incentives. As winter is off peak for many solar installers, sometimes systems and installation costs can be reduced.
• Faster regulatory approval and grid connections: As it is off peak it can lead to faster regulatory approval and grid connections. Application volumes for local councils may be reduced and it can be a quieter season for administrative paperwork to be completed.
• Faster payback during high winter demand: Winter electricity bills are typically higher and installing a solar system during this time means you can start offsetting these high energy costs immediately.

Solar panels are effective all year round, whether in the summer or winter months they will always be producing energy. There are even advantages of having solar in winter although you might expect voltage output to decrease. To find out about having solar installed this winter contact the team at Tasmania Safer Solar.