Do Solar Panels Need Sun or Just Light?


Solar energy has come a long way over the years. Almost everyone has a basic understanding of how they’re mean to work. The panels are out, they collect sunlight, and convert that into electricity. Wonderful cheap green energy. However, some people are curious if sunlight is the only light that converts into energy.

Solar panels are designed to turn any type of light into energy. However sunlight is always the best choice for the efficient conversion of light to power. While solar panels can charge from LED light, incandescent light, fluorescent light, and even street lights, sunlight always provides the most energy from exposure.

But if you’re trying to figure out how to power up solar panels without the sun to save money you’re in for disappointment. It will cost more from those other sources of light than the charging of the solar panel will give back. There’s a reason maximizing the time fully exposed to the sun is the goal of any home or homestead setup.

small cabin with solar panel on a foggy morning
Even during days like this, the light that cuts through still charges the solar panels. Not the same as a bright sunny day, but it’s still solar power at work even during less than ideal conditions.

Designed for Sunlight

Sunlight brings the most bang for the buck. Why? Because the sheer amount of energy that is available from sunlight. The scientifically accepted number is that sunlight provides 1,360 watts of energy per square meter (according to NASA) with some variances, but that is the average.

That is a whole lot of energy. Artificial light isn’t going to be able to put that output out there, especially on a per second basis.

Because sunlight offers so much, this is what solar is based around. So the panels are even optimized to look for the specific UV rays of solar light and to optimize them as efficiently as possible.

Will solar panels grab energy from other sources of light?

Absolutely! But since no artificial light can get even close to what the sun puts out, you won’t see the same numbers.

This is a VERY general rule of thumb, so don’t do mathematical equations off of this, but here are some very basic rules of how light is going to work with solar charging:

  • Solar panels get the most energy from direct sunlight
  • Charging from sunlight on a cloudy day takes 300% longer than on a sunny day
  • Charging with an LED light takes 750% longer than on a sunny day
  • Charging with a CFL light takes twice as many watts as an LED to match the LED light’s charging time
  • Charging with an HID light takes six times as many watts as an LED to match the LED light’s charging time
  • Charging with an incandescent light takes 8-9 times as many wats as an LED to match the LED light’s charging time

Like I said, these are rough rules of thumb, but they show how long it takes to charge solar batteries with artificial light. It’s an inefficient process for sure.

For more accurate and in-depth details on each, move on to these next sections.

Solar Panels & LED Lights

LED lights are generally the best artificial option when it comes to needing an outside source to charge gear. The only times this makes sense from an economic practical standpoint is if you have drained outdoor gear that you have inside, where the LED lights will be on anyway, and you have them out in the open where they can capture light on charge.

Though even then, it’s kinda weird. But it does give you a way to charge up and test your gear to make sure it hasn’t lost most of it’s power if you haven’t used it in a while.

If you are going to use artificial light to charge up solar gear then LED lights are the way to go. But keep in mind even natural daylight from very cloudy days are three times better than what LED will be able to provide.

For an in-depth of analysis check out our article: “Can an LED light charge a solar backpack?” to learn all you need to know and more!

Solar Panels & Iridescent Lights

Since iridescent lights are going to be the most common after LEDs in a house. Light from a traditional iridescent light can be used by solar panels to capture that energy and charge something.

However, it is extremely inefficient and unless it’s a flashlight running on batteries or something, it’s almost certainly going to cost more money and take more energy than

Solar Panels & CFL Lights

Yes, solar panels can charge from the light emitted by CFL lights. Generally speaking, among artificial light sources a good rule of thumb is that CFL lights are going to be the most effective option outside of LED. This is still likely to take way longer than sunlight even on a cloudy day.

As in over a day or more if you’re inside the entire time.

But this is an option and any outdoor solar gear you have like backpacks, portable power stations, etc. can still (slowly) pick up a charge as long as the solar panel is facing the light.

Solar Panels & HID Lights

Yes, solar panels can pick up a charge from HID based lights. As with the other examples on here, it’s far from the best solution but it is an option if you are stuck indoors and for whatever reason don’t want to use the conventional sources available.

However, even being outside on a cloudy or even rainy day will still be more effective light for solar panels to use in order to convert to energy.

Can Solar Panels Charge from Streetlights?

Yes. The amounts are going to miniscule, but this is actually possible. We have the nightly readings from the solar panels at the house to prove it 🙂

Can Solar Panels Charge from Flashlights

Weird question, but yes, they can. So if you have a camping lantern or flashlight that is battery operated or, better, can be crank powered (many survival lights have this feature to always allow someone in a survival situation to produce light) then this can be an option to get a bit of charge in a solar charger.

I’m assuming this is to charge a phone or laptop of an outdoor influencer in an isolated area. It’s odd, and it is NOT at all efficient but this is actually doable.

Do Solar Panels Charge from Moonlight?

The answer is no. Moonlight does NOT charge solar panels even a little bit.

Keep in mind that the moon actually doesn’t put off its own light. The only reason we can see the moon is because photons from sunlight are reflecting off of it.

So the moon isn’t giving of light, and the reflection from the sun is far too little to make a difference.

But what about that blog post I saw showing solar panels gathering energy at night?

Fair question. It’s absolutely possible that the solar panels were capturing some energy at night. But it wasn’t from the moonlight.

Solar panels can grab energy from artificial light sources. This includes flashlights, spill out from house lights, or even street lights if you’re living in a town or city.

The solar panels on the garage at our home setup does register a small (very, very small) amount of power generation at night, but that’s because light from an upstairs hallway, bathroom, and bedroom fall out the window right onto the panel nearest to the house. It’s possible light floating out from the kitchen does the same.

There are also two major street lights nearby that also light up the garage area. Add in the raccoons and squirrels that set off the security motion lights, and it’s not much, but the solar panels are always ready to work.

Unfortunately the full moon nights just don’t do it.

In Conclusion

The final answer is that, yes, you can charge solar panels of all sizes with light other than direct sunlight. However, sunlight is always going to be the most efficient way of doing so. From a cost perspective, the electricity you are spending is going to almost certainly be more than you’re saving.

But in the right circumstances where the lights are going to be on anyway or there’s some sort of particular potential emergency or situation where you need an artificial light to charge solar panels it’s good to know that artificial light is indeed an option.

Shane

Hi, I'm Shane! I've always felt a passion for two worlds: one in technology and one for the great oudoors away from it. The amazing advances in solar power in my lifetime have really opened up the possibilities, and both my brother and I are deeply passionate about where solar power meets outdoor gear!

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