If the sun isn’t shining on your solar panels, they won’t be able to produce energy. When trees or other obstructions are shading solar panels, efficiency losses and reduced power generation may become problematic. In this article we will examine the effects of shade on solar panel production and efficiency.
Do solar panels work in the shade?
Though the output will be reduce, solar panels will still work in the shade – just at less capacity due to lower sunlight exposure. Though the numbers will vary depending on how much shade the panels are facing, the general rule with clouds and shade is that solar panels will produce about half as much energy as they would with direct sunlight.
Where does solar panel shade come from?
Shade on your solar panels can come from several sources.
Trees: Perhaps most obviously, trees near your solar array can cause shading issues. Many residential properties are situated in green spaces, and constantly growing trees and foliage can encroach on solar panel setups.
Other panels: In addition to trees, solar panels can actually be shaded by other nearby panels. Depending on the panel setup, neighboring panels can cast shadows over lower panels in the same system. This issue typically only arises in ground installations.
Your roof: Panels can actually be shaded by the roof they are on. Depending on the sun’s angle and the time of day, different parts of a roof (like a chimney or dormer) can block sunlight to certain panels. Use the EnergySage Solar Calculator to determine the solar potential of your property while factoring in local shading.
Clouds: We can’t discuss shade without mentioning clouds. Despite the fact that clouds do technically block out the sun and cast shade, you shouldn’t worry about solar production on cloudy days. Clouds still let some sunlight through, which means solar panels still can produce energy, albeit at a lower efficiency. You can think about cloudy days and solar production the same way you might worry about getting sunburned on a cloudy afternoon. If you’re outside, you still need to be careful and apply sunblock to avoid getting burned.
Want even more assurance when it comes to solar panels and cloud cover? Take Germany, a world leader in solar production. Germany is further north than the United States – in fact, Berlin is north of Calgary, Canada – and it isn’t exactly known for its sunny days. Regardless, Germany is a solar energy powerhouse, and generates immense power from its photovoltaic units.
Shade and solar panel efficiency
Shaded solar panels produce less power than those in direct sunlight. Exposure to less powerful sunlight is the obvious contributor to lowered efficiency, but the design of your solar installation – specifically, the panels and their inverter(s) – also matters. If your roof is completely shaded for most hours of the day, solar panels may not work well for you, unless nearby trees can be trimmed or removed. However, if your roof only experiences partial shade at certain times of the day, as many residential roofs do, there are solar inverter solutions that will prevent excessive efficiency loss.
Solar inverters are the companions to solar panels – they convert direct current (DC) to alternating current (AC), which is what most homes use for electricity. The right solar inverter also helps minimize efficiency losses from shaded panels. The three types of inverters currently available (string inverters, micro-inverters, and power optimizers) all contend with shade in different ways.
String inverters are the most basic and widespread inverter technology. In a string inverter system, many panels are connected to the same inverter. This means that the entire system can only operate at the power of the weakest panel. For example, if a tree next to your house casts a shadow over one panel in a row on your roof, that entire set of panels will only operate as efficiently as the shaded panel.
A system with micro-inverters will have an inverter installed for each individual solar panel. Micro-inverters operate like a string of Christmas lights – if one light goes out, the rest of the string will still stay lit. In a solar panel array equipped with micro-inverters, if one panel has a shadow cast over it from a nearby tree, the rest of the panels around it can still operate at peak efficiency, because each panel in the array has its own designated inverter.
Power optimizers are akin to a combination of string inverters and micro-inverters. Instead of a micro-inverter at each panel, power optimizers at each panel “condition” the DC electricity generated from the panels and send it to a single string inverter. Similar to micro-inverter systems, power optimizers can help negate the effect of a single panel being shaded on an entire system.
If you expect that your solar PV system will be partially shaded for a significant part of the day, consider installing a system with power optimizers or micro-inverters. These inverter options will be slightly more expensive than a standard string inverter, but they can also result in higher electricity production (and therefore greater long-term savings).
Find the best solar setup for your unique property
Shade causes variations in solar generation, but these variations and dips in efficiency can be minimized no matter where you live through panel layout and inverter selection. Solar installers can customize installations for your property based on shading, among several other factors, to give you the best and most appropriate solar setup. Visit the EnergySage Solar Marketplace to get custom-designed quotes at no cost from solar installers near you. Questions about shading on your property can simply be added as a note in your property profile.