Do Solar Panels Need Direct Sunlight?

Homeowners who are starting to research solar panels often wonder if they need direct sunlight. The simple answer is that solar panels can generate electricity even in indirect sunlight caused by clouds, rain, shade or snow. 

Let’s take a look at how solar panels work, how the amount of sunlight impacts the amount of electricity they produce, and some technologies that can get better performance out of them.

Direct Sun And Solar Panels: How They Work Together

At a high level, here’s how solar panel systems generate electricity: Photons from solar radiation – another name for sunlight – hit the photovoltaic cells. When they hit with enough force, they separate electrons from atoms. This creates an electrical current.

At this point, the electricity is direct current (DC) and it flows from the solar panels into the inverter. The inverter converts the DC into alternating current (AC) that can power the appliances in a home.

Direct Sunlight Is Often Best For Solar Panel Production

More of the sun’s rays will hit solar cells on a sunny day, leading to higher power output from the system. Sunlight pouring down onto solar panels is generally good thing, but only to a certain point.

Sunlight can also result in high temperatures, thereby degrading performance. That’s true for many electronics. For example, think of what happens when your smartphone gets too hot.

While direct sunlight is great, an occasional bit of cloud cover keeps solar panels a bit cooler and may improve their performance as a result.

Peak Sun Hours: How Much Sunlight Solar Panels Need

A peak sun hour is when 1,000 watts of solar radiation, on average, falls on one square meter in a given amount of time.

Generally speaking, homes in the U.S. that receive 4 or more peak sun hours per day are considered good for solar installations. Southwestern states and California receive some of the highest sun numbers per day, on average.

Some southwestern states, including New Mexico, have aggressive goals for increasing solar generation capacity. A midwestern state, Illinois, also has policies making it more affordable for homeowners to install solar energy systems – even with an average sun number of less than 5. That’s still enough sunlight to make solar worth it.

Do Solar Panels Work In The Shade?

What happens to solar panel performance on an overcast day? If some sunlight gets through the cloud cover, a PV array might generate 80% of its maximum output.

Shading tends to block more sunlight, though. Unlike clouds, which let some solar radiation through, shade tends to be from a physical object like a tree or building. These obstructions don’t let any light through.

A panel that’s 25% shaded may experience a 50% drop in production, while a panel 50% shaded could experience a 90% drop in production, although the exact numbers depend on your unique solar situation.

There are some technological solutions to partially shaded solar panels. They may not result in the same production as an array constantly in direct sunlight, but they can mitigate problems with shade. Up next is a high-level overview.

Microinverters

Older central inverters, also known as string inverters, are prone to shade issues. If one panel is shaded, it decreases production in the other panels. That’s because central inverters reduce the maximum current to the output of the lowest-performing panel in the array. Microinverters allow each panel to perform at their individual best. Microinverters also have other advantages compared to string inverters.

Power Optimizers

If you already have a solar array with a string inverter, power optimizers can give your array some of the benefits of microinverters. Power optimizers allow maximum power point tracking (MPPT) at the individual panel level, which lets each panel provide a maximum amount of power even when other panels in the string produce less power.

FAQs: How To Deal With Solar Power When The Sun Isn’t Shining

Homeowners often ask these questions about living with solar panels in places known for cloudier weather conditions.

Will my house still get power if my solar panels aren’t producing as much?

Most homes with solar panels are grid-tied, which means a local utility company provides power for the home at night and during cloudy weather. The process is seamless and requires no action from the homeowner.

If your utility company offers net metering, your solar power system may allow you to get credit for excess energy it adds to the grid. Net metering is often a major incentive for homeowners to go solar and produce renewable energy.

Should I get a solar battery?

A backup solar battery can be a great investment, especially if your local government agencies or utility companies offer good incentives. However, it’s not a necessity for homes that experience frequent clouds or partial shade. Battery storage often makes sense for homes in areas that have frequent power outages or high charges using electricity during peak hours.

Direct sunlight is often ideal for producing clean energy with solar panels. However, homeowners and utility companies in areas with less direct sunlight and lower sun numbers often produce a worthwhile amount of energy. Cloudy days don’t stop sunlight from reaching the panels, and emerging technology can provide more energy production even in partial shade.

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