How Solar Works When It’s Not Sunny

It’s well-known that going green and installing a solar panel system on your home reaps both environmental and financial benefits, but to some just learning about the technology, it might be confusing how solar systems can provide electricity consistently throughout the day. After all, the sun isn’t always out; clouds and rain happen, and then there’s nighttime. How do solar systems work when it isn’t sunny?

Most modern solar installations at homes and businesses are photovoltaic (PV) grid-tied systems. Photovoltaic means they collect sunlight and convert it to electricity. Grid-tied means they’re connected to the regional energy “grid,” of which your local electric is a part. When it’s a sunny day and your home is generating more electricity than you’re using, the utility grid takes what energy you don’t need from your system and sells it to others who do need it. The power company pays you for this electricity in the form of a credit.

When your system isn’t producing enough electricity for your home’s needs, you draw power from the grid, just like any other home that’s connected to the electric company. But because you sold them electricity earlier, the credit you earned reduces (or even negates) what you have to pay for what you draw. This energy-efficient process is called “net metering.”

Switching back and forth between drawing power and selling power may happen during the same day. If you’re away from home during the sunniest part of the day, your home probably uses less power than it consumes. Then when you return to home after work and the sun goes down, you consume more power than your system produces, until you leave for work the next morning.

However, you don’t necessarily rely on power credits to power your home during non-sunny times. Grid-tied solar panels still produce electricity on overcast days, though it might be at only 10 percent to 25 percent of their capacity. The amount of sunlight that gets turned into electricity on a cloudy or foggy day depends on the density of the clouds and the efficiency of the panels. Depending on the cloud cover, you might even end up producing more power than on a clear day, because sunlight that bounces off the earth can be reflected by clouds right back down again.

Speaking of reflected light: moonlight, of course, is just sunlight reflected by the moon. This makes it possible to produce a little bit of solar power at night if there’s a full moon and the weather is clear. But don’t expect it to power your refrigerator. The amount of electricity produced by moonlight is negligible even under ideal conditions.

Fortunately, most places in the United States get more than enough sunshine regardless of low-sun days for grid-tied solar power to make economic sense for most homes and businesses. This is the case in the tri-state area of Pennsylvania, New Jersey and Delaware, when TerraSol Energies, Inc., provides solar power installation and service. Contact us for a free consultation and estimate: 888-873-9995.