Do Solar Lights Charge On Cloudy Days?

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As solar cells generate power by the bombardment of photons present in sunlight, the degree to which they perform depends entirely on how much sunlight comes in contact with them.

In short, solar lights can and do charge on cloudy days, though the amount of charge is relative to the amount sunlight available.

The key to understanding just how well your solar light will charge, lies in understanding how clouds can cause the deflection of photons – the vital variable that causes the power generating electron flow within a solar cell.

A Brief Look At How Solar Cells Work

Super simplified, solar cells are a lot a billiards table. Things are calm and stable until the cue ball comes along and strikes the other balls.

Once this impact takes place, things are set into motion. The greater the impact, the greater the resulting motion.

A solar cell operates in a fairly similar manner, except instead of a cue ball impacting other balls, photons present in sunlight impact with the electrons present in the solar cell.

Also, unlike billiards which has only one cue ball, there are many photons present in sunlight. Imagine the chaos on a billiards table if there were multiple players driving cue balls into the fray!

For an in-dept look at this process, please read, ‘How Do Solar Panels Work?

Deflecting Photons

Continuing our billiards example, impact works best when a clear path is available. ‘Bank shots’ can work, but some of the driving energy is lost. And if your goal is to really move the other balls, then you want as much energy as possible when coming in contact with them.

Clouds are essentially obstructions for the driving photons present in sunlight. Some clouds result in ‘bank shots’ for the photons, while others result in a ‘soft strike’. The impact to photon energy depends on the make up of the cloud itself.

Types Of Clouds

In solving just how clouds can impact photon flow, one must look at the different types of clouds.

  • Big white fluffy clouds – These type of clouds that periodically float across the sky are, for all practical purposes, a non-event.

It has been my experience of living off-grid, completely on solar power, that power generation in these conditions is relatively unimpeded. Granted, the more of them, the greater the impact. But generally speaking, these pose the least threat to solar power.

  • Haze – It is not uncommon, especially in areas of high humidity, to have a permanent haze in the sky (the sort of condition that allows you to look directly at the sun without having to shield your eyes).

This is type of cloud cover does impact photons. It does not impose a complete obstruction, but it does certainly affect the amount and energy of the photons striking the solar cell of your solar light.

  • Rain clouds – Rain clouds are especially challenging for power generation as the concentration of obstructive material (aka moisture/rain) is very dense. Not only do the clouds themselves offer a great resistance to photon movement, but the rain water running across the solar cell plays a part in reducing power generation.

Solar Light Engineering

While the bulk of this article has been dedicated to cloud cover, there is something to be said about how your solar lights are engineered.

There are three other factors that have a direct impact on how your light will perform after a cloudy day.

  • Solar cell – Sizing a solar cell to power your solar light may have more to do with manufacturing costs than the environmental conditions relative to your exact location. This could result in either a solar cell that exceeds power requirements… or comes up short.
  • Battery makeup – There are many different ‘flavors’ when it comes to energy storage. The battery in your solar light must have the proper balance between capacity and longevity. A discrepancy in either, will show in the event of a cloudy day.
  • LED – LED’s are incredibly energy efficient. However, if too many of them are installed, they will drain your power supply fast. This will also contribute to poor performance in the event of inadequate sunlight.


Making a purchase that performs to expectations depends on one buying the appropriate light for their individual needs and environment.

If you live in area with good sunlight, then you will have a great deal more flexibility in your decision process than if you live in an area with a great deal of cloud cover.

Generally speaking, if the battery in your solar light doesn’t get a full charge, then it doesn’t mean the that light isn’t going to work, but rather it won’t work as long. So be sure to factor in, just how long you need to the to work. You may find yourself able to lean more to aesthetics than hours of illumination.

For more on this, please read, ‘3 Different Types Of Solar Flood Lights.’

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