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Can You Charge a Solar Panel With a Light Bulb?

There’s no doubt that the effects of solar panels are amazing. They can power just about anything, too! But what if you don’t have access to the sun and need a charge on a solar panel? That leads us to the main question and topic of our article.

Can you charge a solar panel with a light bulb? You can charge a solar panel with a light bulb, yes. However, it’s relatively inefficient and counter-intuitive. It will also take much longer to charge a solar panel with a light bulb than with natural sunlight.

Can you charge a solar panel with a light bulb?

We’ve compiled the important things you need to know about charging solar panels with light bulbs, like how solar panels work, what types of things solar panels can produce energy for, and how you can charge a solar panel with a lightbulb – albeit inefficient and slower.

An Overview of Solar Panels and Charging

To explain to you how to charge a solar panel with a light bulb (and why it’s not your best option for charging a solar panel) it’s important that you first know some of the basics about solar panels.

Solar panel basics

To put it very briefly and simply, solar panels are objects that are generally made up of photovoltaic cells that absorb sunlight and convert it to useable energy.

When you think of solar panels, you may think of the large solar panels that are on the ground or on the roofs of homes. You’d be correct, those are indeed solar panels.

Additionally, there can also be smaller solar panels and other solar components that power smaller items, like watches, flashlights and outdoor lights.

Solar panels are often a part of an entire solar system to absorb and convert sunlight to energy, as is the case with solar panels that are on the roof of a home. Solar systems also usually include inverters, rackings, batteries, and charge controllers in addition to solar panels.

Charging solar panels with artificial light and light bulbs

You’ve learned by now that you can indeed charge solar panels with artificial lights. How is that possible? As it turns out, it has to do with the types of light waves and light spectrums each form of light produces.

Light waves and light spectrums

Natural sunlight and artificial light both put off light waves that solar cells can respond to and absorb. However, solar cells respond differently to different light waves. 

The difference in charging solar panels with lightbulbs (and therefore, artificial light) has to do with the light waves each different type puts off. Because the light waves in each type of light source is different, solar cells respond to and absorb them differently.

Solar cells are so responsive to the sun’s light waves because they roughly match the Sun’s spectrum of light. Therefore, it can more easily absorb and respond to those light waves.

The light waves that come from incandescent or LED light bulbs are different than the light waves that come from the sun. Because of that, the solar cells absorb and convert some of the light waves, while ignoring others.

Lightbulbs you could charge a solar panel with

Now that you know that different types of light put out different light waves and have different light spectrums, you can understand what we’re about to get at next: there are actually light bulbs that are better for charging solar panels with than others.

Again, this has to do with light waves and light spectrums, but it also has to do with power and efficiency.

First, you should know that there are different types of light bulbs and artificial lights that are commonly used, including:

  • LED light bulbs
  • Incandescent light bulbs
  • Fluorescent light bulbs
  • UV light bulbs

You can, in theory, charge a solar panel with any of these light bulb types. However, if you’re considering charging a solar panel with a light bulb, an LED light bulb is going to be your best bet. There are a few reasons for this.

First, LED light bulbs are more efficient at converting electricity to light than other light bulbs, while also being safer and less hot than other light bulbs.

LED lights are about 80% efficient at converting electricity to light. This means 80% of their energy is converted to light, and the other 20% is converted to heat. In comparison, incandescent light bulbs are the exact opposite; they are 20% efficient at converting energy to light. The other 80% of their energy is converted to heat.

Since LED lights are more efficient, they produce less heat. It may seem weird, but direct intense heat can actually damage solar components, especially small ones that you might see in a solar watch or a flashlight. So, if a light bulb is more efficient and less hot, it’s much better.

Tips for charging a solar panel with a light bulb

If you’ve decided you want to try charging a solar panel with a light bulb either as an experiment or for another reason, there are some tips that are important to be aware of.

First, the higher the wattage of the lightbulb means the higher the charge it can produce. For example, on a normal, sunny day, the sun produces about 1,000 watts of solar energy per square meter on the Earth. A typical lightbulb produces anywhere from 40 to 100 watts total. 

Next, keep a safe distance between the solar panel and the light bulb when attempting to charge one with the other.

This is especially for small panels like those that are in flashlights, solar lights, garden lights, and watches. Keeping the panel at least 20 inches away from the light bulb is a good rule of thumb.

Reasons Why You Should Avoid Charging a Solar Panel With a Light Bulb

As you know by now, it’s entirely possible to charge a solar panel with a light bulb. However, that doesn’t mean it’s very efficient or useful. In fact, it’s actually pretty inefficient and counter-intuitive.

Let’s dive into why you should try to avoid charging a solar panel with a light bulb and just stick with natural sunlight for charging.

Natural sunlight is more efficient

Efficiency, efficiency, efficiency. You’ve read quite a bit about efficiency in this article so far, and we promise it’s for a good reason. Efficiency is important.

One of the reasons solar energy is so revolutionary is because it’s so efficient; we can harness energy right from the sun and use it to power many of the things in our everyday lives.

You already know this, but light from the sun is free. We can’t say the same for the light that comes from a lightbulb.

The point is, why charge a solar panel with artificial light that costs money and energy, when you could harness the energy for free from the sun?

Unless you absolutely need to charge a solar panel with a light bulb, or unless you’re looking to do a fun experiment, you should probably just skip that method all together for actual power and efficiency.

Charging solar panels with natural sunlight is much faster

Sure, you can charge a solar panel with a light bulb, but the going is slow (and we mean really SLOW).

Let’s take charging a solar watch, for example. Solar watches are meant to be charged by natural sunlight, but they can also be charged by artificial light (like a light bulb).

To get a solar watch to a full charge using direct natural sunlight, it only needs to charge for about 20 hours.

To get a solar watch to fully charge in artificial (LED) light, it needs to charge for 150 hours, and even then, it can potentially be harmed by the heat given off by the LED light. Simply put, it’s much faster to charge a solar panel with natural sunlight than it is to charge a solar panel with artificial light (especially just a lightbulb!).

Title image by Marco Verch