Should I add solar when I reroof? Have you been thinking about adding solar panels to your roof, but you’ve been told that you have too much shade? While shade does affect the efficiency of solar panels, it is less of a concern today than it was several years ago. In some systems, a shadow cast on one panel can affect the efficiency of the entire solar panel array. But with many modern inverters and solar power systems, inefficiencies due to shade coverage can be limited.
As you’re probably aware, solar panels need direct sunlight to convert light to energy. The more sunlight your roof is exposed to, the more efficient your panels will work and the more energy they’ll create for the homeowner.
Trees play an important role in many leafy city suburbs, but they are often considered problematic when you want to reduce your home’s carbon footprint by adding solar panels. It may not be possible to cut back trees in many suburbs due to local regulations. If your home is next to tall buildings, your solar panels can be affected by shade during the winter months.
At SOllOS, we can answer some of the many questions about shade and solar panels. We’ll offer solutions to installing solar panels when your home is covered in partial shade, either due to trees or tall buildings.
Should I add solar when I reroof?
Solar panels will still work in the shade, but their efficiency will be reduced. Solar panels require unrestricted light to work at peak efficiency, so the more things that limit the amount of light they’re exposed to, the less energy they can collect.
The most common causes for shade on solar panels are tree cover, roof type, other buildings, and the weather. Out of these three, trees are usually the easiest to deal with because you can remove any branches that shade your panels. If you need to remove tree branches, it is best completed before installing panels. After your panels are installed, you’ll need to monitor trees as they grow and regularly trim them back.
The type of roof you install panels on can create patches of shade. For example, if you have a split roof and one is significantly higher than the other. In this case, installing panels on the lower roof can result in them being shaded during parts of the day.
The weather you experience will also affect your solar panels. Unfortunately, there is not much that can be done about cloud cover and rain. If you’re concerned about your power use and generation abilities during inclement weather systems, you can install a battery storage device.
Why does shading have such a dramatic impact on energy production?
Solar photovoltaic (PV) systems designed for residential homes and businesses will include solar panels (often referred to as an array) and an inverter. The solar panels will work as a filter and extract energy from light as it passes through and converts this energy to direct current (DC) electricity. DC is not usable by most homes, and the inverter will take on the job of converting this energy into alternating energy (AC), which can be either used by the home or transferred into the energy grid.
In a standard solar power system for homes and small businesses, your solar panel array will be made up of six to thirty panels. However, solar panel systems are often known by their capacity, measured in kilowatts (kW). If you ask a homeowner about their solar panels, they likely know the kW, but they’ll need to count how many panels. Many modern solar panel arrays are separated into strings. These strings can be one panel, but they are usually more. Small home solar power systems will only have one string, but larger ones may have more. It all depends on how the system was installed.
The strings in a solar panel system are a lot like water pipes. The energy flows through the pipes and into your inverter. However, when shade affects one of your solar panels, it can be like a tree root blocking a pipe. The shade will act as a blocker and stop the energy from flowing. The strength of the shadow will change the efficiency of the panel. For example, if the panel is half-covered by a solid shadow from a building, the efficiency will be limited to about 50%. In contrast, if the dappled shade of a tree covers the panel, then the efficiency may be reduced by 30-40%.
In old solar panel systems, shading on one cell could affect the entire panel! However, many modern solar panels use newer technology (such as bypass diodes) to minimise the effects of shade on solar panels.
Bypass diodes allow for the energy generated by solar cells to flow around shaded cells. Instead of a single pipe, it is more like a shallow river, and the shadow acts as rocks, but the water can flow past in the places of least resistance. However, bypass diodes require a certain amount of shade to affect a panel before they are activated, restricting their effectiveness.
Avoiding shade for the best results with your solar panels
The best and easiest way to avoid problems associated with shade is to install your solar panel array so it won’t be affected. Before installing the panels, you need to consider all times of the day and how the roof is exposed each month of the year. For example, a section of your roof may only get 10% shaded in summer but 75% shaded in winter. In this scenario, it may be best to install the panels on your roof where you get 20% summer shade and 30% winter shade.
For the best results, you can have a solar expert review your home and determine the best location for your solar panels. Solar installers use a host of modern tools to decide if your home will be affected by shade.
After the panels are installed, it is up to the homeowner to make sure any trees nearby are maintained properly. This may involve engaging the services of a qualified arborist to trim overhanging branches while maintaining the tree’s integrity. If your home is located in an area where tree removal is discouraged, you may need to seek approval before modifying trees on or near your property. If the branches pose a significant risk to property, approval will often be granted, but this may require the services of a tree inspector.
As solar panels will last around twenty-five years, it gives trees plenty of time to spread their branches. For the best results, have any nearby trees inspected every five years to ensure they’re not affecting your solar panels.
Clouds are another potential cause for shading on solar panels. However, shade from clouds is completely unavoidable. As a guide on cloudy days, your solar panels will produce 25-45% of the energy you’d expect in ideal conditions. The average cloudy days you can expect in Australia is 150, but this will vary based on your specific location.
Choosing the best inverter for shaded homes
If you can’t position solar panels or remove trees (and buildings!) to reduce the impact of shade, your other option is to choose a more suitable inverter. Solar inverters are required to convert the DC power of solar panels into AC to be used by the home. You can think of an inverter as like the engine in your car, and the panel is the petrol. You need good clean petrol, but with an engine to convert the petrol into energy you can use, you’re not going very far!
When looking at inverters, there are three main types to choose from: string inverters, micro-inverters, and power optimisers. These inverters all deal with shade in different ways.
String Inverters
String inverters are basic inverters, and these are seen in most solar panels systems installed today. All the panels are connected and work together as a complete unit. Unfortunately, if one panel is not working at peak efficiency due to shade, the entire system is affected.
If you have one panel constantly affected by shade and a string inverter, then it may be best to remove or reorientate that panel so your system can perform more efficiently. However, in most situations choosing a different inverter is the better choice.
Micro-inverters
A micro-inverter system will have inverters installed on each solar panel. These inverters operate similarly to modern LED string lights. If one light goes out, it doesn’t affect the rest of the lights in the chain. When a shadow is cast on a panel in a micro-inverter supported system, only that panel drops in efficiency instead of affecting the entire system.
If you cannot avoid shade on your roof, micro-inverters can be an excellent option. Installing a system with micro-inverters will have a higher cost. But as the system will be more effective in shaded areas, the higher cost is worthwhile.
The advantage of a micro-inverter solar system is you don’t have a high voltage DC system on your roof. Also, there is no central point of failure; if one micro-inverter fails, you can replace that one instead of the entire system being out of action.
Power optimisers
Power optimisers are essentially a combination of string and micro-inverters. A power optimised system uses power optimisers instead of micro-inverters at each panel. The power optimisers will condition the DC electricity before sending it to a string inverter. The results from a power optimiser system are similar to a micro-invert system, and it can negate the effects of having one panel affected by shade.
The main advantage of installing power optimisers is that you can install them only on the panels affected by shade. Installing a solar panel system reduces the costs you’d typically expect with a micro-inverter system.
Which inverter style is the best?
There are pros and cons to using any inverter style. If your roof is affected by shade, it may be best to avoid using only a string inverter. If you’re looking to save money on equipment costs, a system designed with power optimisers may be the best solution. For a homeowner, after flexibility and increased safety, micro-inverters could be the best option.
Talking to your solar panel provider will give you a good insight into the best system. All homes are different, and each system may have additional pros and cons. The more information you can provide your solar panel provider, the better advice they can provide.
Use the best solar panels and inverter set up for your property
After talking to your solar panel provider, you’ll know the best solar panel system for your roof. But, the choice is still yours to make. If you want to save money on the installation costs and deal with the reduced efficiency rating, then perhaps a system with a string inverter is your best option.
However, if budget constraints are not an issue, and you want to ensure your solar panels deliver the maximum amount of power during the shade, rain, and cloud coverage, then micro-inverters or power optimisers are ideal.
Installing a string inverter system is probably your best option for a home with no shade issues, such as a farm property, or you live in a new suburb. In this system, you can trim any trees as they grow. However, if you’re in a new suburb and the neighbouring properties have not been built, you can wait to see if you’ll be affected by shade or install an optimised system that factors in potential building shade.
At SOllOS, we use various tools to make sure the panels we install are positioned to be the least affected by shading. If you’re thinking of installing solar panels and are concerned about shade, give SOllOS a call, and we will provide you with a range of suitable options.
Also read: Can I install solar myself?