Can a Light Bulb Charge a Solar Panel?

As an Amazon Associate, this site earns commissions from qualifying purchases. For more details, click here.

Can you charge solar panels with a light bulb? If you can charge a battery with electricity, why not PV modules with lights? There will be days when the sun won’t shine as brightly as we would like, so can a LED or incandescent light be an alternative?

You can charge a solar panel with a light bulb, but it is not an efficient method. LED bulbs convert only 20%-30% of light into electricity, not counting the energy losses from the solar panel and inverter. You have to use a reflector lens concentration device to focus a light bulb into the panel for better results.

How to Charge a Solar Panel with a Light Bulb

If you still want to do this, it is very easy. Get a light bulb, turn it on and position the solar panel at least 20 inches from it. Your solar power system should have an indicator that will notify you when it is fully charged.

The basic steps are simple but the key here is its efficiency. Here are some tips that can speed up the charge.

Use a LED Bulb. LED bulbs have a 20% light into electricity conversion rating. Some high end LED bulbs may go as high as 40%-50%. By comparison, incandescent light bulbs are only 10% efficient.

LED bulb has many advantages over incandescent, but in this case the most important is its efficiency. Solar panels are not 100% efficient either so you need to make up for that with a good quality light bulb. When it comes to converting light into electricity, LED is superior to incandescent.

Use a high wattage bulb. On average the sun generates a thousand watts of energy per sq m on the planet. No one expects a light bulb to produce that kind of power. But use the highest wattage LED bulb available. For value and quality we go with the Sylvania LED Light Bulb Value Line.

An average LED bulb generates anywhere from 40W-100W. If you are going to recharge solar lights, portable solar chargers and other small solar panels, a a few of these light bulbs will do. For larger solar panels you will need several of these.

As for solar panel, you should go with something small. If you just want to find out if this will work, the 30W Newpowa 12V Solar Panel is just the right size.

Proper Distance. As we mentioned the ideal distance is at least 20 inches. You do not want the light bulb and sola panel too close, but you don’t want it too far apart either. For charging small solar powered devices, 20 inches or about two feet is right. For larger ones, you have to experiment to see which works best.

Sunlight vs. Light Bulb Solar Charging

In our comparison of hydro, wind and solar, we pointed out why solar is the most ideal for homes and individuals. And mainly it is because of efficiency. Sunlight is freely available and offers many advantages over light bulbs.

Sunlight is free. This is stating the obvious but it is true. We use the sun to power solar panels at no cost. Once you buy the solar panel you don’t have to pay for anything else. You get free energy. As long as the solar panels are well maintained, they will run for decades.

LED bulbs are affordable but free is better. Second, the low cost will quickly rise because you have to buy several LED light bulbs to charge a solar panel. If you are using incandescent then the cost will be even higher.

The bottom line: charging solar panels with a light bulb, or any other artificial light, is not as effective compared to the sun. You should only use indoor or artificial lights as a last resort. This is why most solar power users have a battery bank so they have reserve solar power in case it rains.

If you need another reason not to use light bulbs, here is one: they are very slow. You can charge a solar watch under direct sunlight in twenty hours more or less. With a LED bulb it will take 120-150 hours or more. Now imagine charging an entire solar panel. Even if you have an array of LED light bulbs, it will take a very long time.

And that again brings to the reason why light bulbs are inefficient. One of the many benefits of solar power is you will save money on electricity. You will no longer be dependent on a power company, or at least reduce your reliance on them. Using light bulbs to recharge PV modules defeats the purpose. You will end up spending a lot of money on light bulbs when the sun is out there free and more efficient.

How to Make Light Bulb Solar Charging Faster

The only time it makes sense to use light bulbs is if it’s the only option. If the sun has gone down and you don’t have a battery, then indoor charging via LED is the best option. Aside from the guidelines above, you can use the following tips as well.

Clean the Solar Panels. Remove dust, grime, dirt thoroughly and the panels will charge faster. Water is enough for most cases, but if the cells are really dirty you may need to use soapy water. Refer to your solar panel manual for any recommended cleaning solutions. Do not use strong detergents to remove the dirt. It will damage the panel and you will have to replace it. Since you will only charge small panels on light bulbs, cleaning should not be a problem though.

Choose the Right Position. Solar panels need as much sunlight as possible, and the same principle applies to light bulbs. Position the bulb so it is directly in front of the panel. If you are using several light bulbs, arrange them so the panel receives maximum light.

Be Patient. It will just take more time to recharge a solar panel with a light bulb, period. You need to be patient. As long as the solar panel is not completely depleted, it will get a good charge.

Light Bulb Solar Charging FAQ

Should I Position the Light Bulb Directly in Front of the Solar Panel?

Direct sunlight generates more energy, but it is not necessary. With light bulbs however, it is best to focus as much of the light as possible. Solar panels incur energy loss and so do light bulbs. Combined, the losses will reduce the amount of power that goes in the panel, resulting in a longer charge.

Can I Use a UV Lamp to Charge a Solar Panel?

UV lamps generate more energy than LED bulbs, so potentially it could lead to faster charging. However they also produce more heat which can be dangerous. Using several UV lamps for solar charging is just too risky so we suggest LED bulbs instead. For a quick charge a UV lamp will do fine, but otherwise it is best avoided.

What Kinds of Light Can Charge a Solar Panel?

Any type of light can be used as long as it is in the right spectrum (visible light, infrared, ultraviolet). The difference makers are the wattage and conversion efficiency. There are many, many kinds of light, but LED is the best for charging because of its efficiency.

Can Light Bulbs Really Charge Solar Panels?

Yes, light bulbs and other artificial indoor light sources do work. Indoor lighting is not as effective as natural sunlight, but it works the same way when it comes to solar panels. Basically the PV modules will convert the light hitting the surface into electricity. It does not distinguish between natural or artificial light.

Does the Weather Affect Light Bulb Charging?

As long as the light bulb is indoors there is no effect. Unless of course the power suddenly goes out.

Can I Charge Solar Powered Appliances with a Light Bulb?

Yes you can, but it is going to be slow, very slow. A computer requires a hundred watts at least, and a solar powered freezer much more. Light bulbs are best used for charging a flashlight or other gadget that does not need a lot of power.

When is the Best Time to Charge a Solar Panel with Light Bulbs?

The best time – and many will say the only time – is for emergency use. If your solar generator or battery bank is not working, or you just need to quickly recharge a solar powered flashlight. In those cases a light bulb will do fine.

What LED Bulb Size is Best For Solar Panels?

You should get a 40W-100W bulb. The higher the wattage the more efficient the charge will be. It also depends on the state of the panel and how much charge it needs.

Can a Light Bulb Charge a Solar Battery?

Yes, small batteries can be charged with incandescent or LED lights. It is not practical for large batteries however. Not only do light bulbs lack the power, but it is going to cost too much to power a good sized battery.


LED bulbs are real energy savers, but they still have some ways to go before being an effective solar panel charger. Solar panels are meant for outdoor use, so charging indoors with light bulbs will be a challenge, at least for now.