Do solar panels need direct sunlight?

Key Takeaways:

• Solar panels work best with four to six hours of direct sunlight per day.

• Solar panels can work with indirect sunlight but with less output.

• You may have to remove tree limbs or whole trees so your system can work at peak efficiency.

Your solar panels are tested to produce a certain wattage at full sun, but real life doesn’t always cooperate. Your panels can produce reduced power from indirect and diffused light, though. To make the best of your environment, trim branches and have a solar company optimize the placement of the panels. We’ll show you how solar panels work with and without direct sunlight below.

Solar panels need direct sunlight for best performance

Solar panels deliver the best energy output when they receive uninterrupted direct sunlight, typically requiring four to six hours of peak sun exposure during midday. Photovoltaic cells operate most efficiently when solar radiation strikes them at a perpendicular angle. The light excites electrons in the silicon cells, which create an electrical current. 

Your panels will generate electricity at their rated capacity when these conditions align:

• Positioned at a 30- to 45-degree angle

• Facing south (if you’re in the Northern Hemisphere)

• Free from any shading obstacles

• Properly oriented to match your location's latitude

Panels are less efficient with indirect sunlight

Modern solar panels harness both direct and scattered sunlight for electricity generation, though performance varies significantly with light conditions. During overcast weather, panel efficiency typically decreases to 23% to 67% of rated capacity. Monocrystalline panels are best for diffused light conditions since they’re more efficient than polycrystalline. (Monocrystalline efficiency ranges from 15% to about 22% while polycrystalline ranges from 13% to 16%.)

If you know your solar panels will have less-than-ideal light, it’s important to make them as efficient as possible. You can:

• Use high-quality MPPT inverters

• Use smart modules with integrated power optimizers for real-time management

• Orient and tilt the panels in the proper directions

• Regularly maintain panels for the best light absorption

Be aware that the best equipment costs more than an entry-level installation.

Another way to overcome having less light in an overcast climate is to oversize your solar panel system and get battery storage. Then, you can use energy from the battery when your panels generate less. You’d also have security for power outages with a battery.

Why can’t solar panels be 100% efficient?

Even the best commercial silicon solar panels on the market only reach efficiencies of around 23%. This means 23% of the energy from the sun is converted into electricity. Why? 

Silicon solar panels can’t be 100% efficient because of inherent material limitations, thermodynamic losses, and light wavelength spectrum limitations. Not all photons have enough energy to excite electrons in the silicon, and excess energy dissipates as heat. Other losses from resistance and charge recombination further limit efficiency.

Do solar panels work under trees in the shade?

Solar panels do work under the shade, though output depends on many things. Dense tree canopies can reduce energy production quite a bit. Deciduous trees drop their leaves in the winter and allow more light at that time while evergreens make constant shade. The angle of shade, time of day, and seasonal sun position all affect power generation capacity.

Modern solar technology has ways to continue generating power efficiently in the shade. Whether you want to use microinverters or modern string inverters, as long as you have modern panels you shouldn’t notice a huge difference if one panel is shaded while the others have full sun. Older solar panels don’t perform as well with partial shade when set up with a string inverter, but new technology has fixed this solar panel issue.

Vents, chimneys, and neighboring buildings also make partial shade on solar panels during the day. If you know you’re dealing with obstacles, look into shading tests by different manufacturers or consult a local solar installer that works with many brands.

Do you need to remove tree limbs to install solar?

It can be a good idea to remove some tree limbs if they cast large shadows on your roof. However, you should weigh the pros and cons of removing entire trees if that’s what an installer recommends. If you enjoy having old-growth trees in your yard, perhaps solar isn't right for you.

• Do a site survey: Walk around your property at different times of day and during various seasons. Notice how shadows fall on your roof or installation area. If large portions of the area are shaded during peak sunlight hours (typically between 9 a.m. and 3 p.m.), it may indicate that tree limbs are interfering with optimal panel performance.

• Use shading analysis tools: Tools like a solar pathfinder or shade analysis apps can help you quantify the impact of nearby trees. These tools create a map of your site’s sun exposure throughout the year, making it easier to pinpoint problematic limbs. 

• Consider the length of shade: Even if there’s some shading, it might not be a deal-breaker. Panels can often tolerate short periods of shadow, especially outside of peak sun hours.

• Think about the time of year: Keep in mind that the time of year affects a shadow’s position and length. A tree next to your house might not cast a shadow on your roof in the summer but it could in the winter.

• Consult with multiple installers: Reputable solar installers can perform a detailed shading analysis and advise whether tree limb removal or trimming is necessary. The analysis should include quantified energy data comparing panels with and without the shade.

• Review local regulations: Sometimes, local ordinances or homeowner association rules can restrict tree removal. You should be able to remove branches, though.

Bottom line: Solar can be worth it with less direct sunlight

While solar panels perform best under direct sunlight, they can still be a good investment even with less-than-ideal light conditions. You can optimize panel placement, trim tree limbs, and use advanced inverters to get the best energy in lower light. And don’t forget that output is just one part of the equation. You could have an expensive energy bill that makes solar savings worth it even in a shaded area or cloudy region.

FAQs about solar panels and direct sunlight

Below are a few frequently asked questions on whether solar panels need direct sunlight.

How efficient are solar panels without direct sunlight?

Your solar panels still work without direct sunlight, though overcast skies can reduce output by 23% to 67%. You'll get better results from monocrystalline than polycrystalline panels and from modern panels and inverters.

How many hours of sunlight do you need for solar panels?

You need four to six hours of daily direct sunlight for effective solar panels, ideally. The energy you get depends on panel angle, shade management, and your location's weather patterns.

Do I need to remove tree limbs or trees to install solar panels?

Not always. But if large tree limbs consistently cast shadows during peak sunlight hours, removal or trimming may be necessary. A professional shading analysis can help you decide.