How Dark Does It Need To Be For Solar Lights To Come On

Are you contemplating the addition of solar lights to your home? If so, you’re likely pondering a crucial question: “How dark does it need to be for solar lights to activate?” This article provides a comprehensive answer, stating that solar lights typically turn on when the ambient light falls below 4 to 5 lux. For context, a moonlit night registers at 1 lux, while complete darkness is below 0.05 lux.

  1. The Role of Lux Scale: Understanding the lux scale is pivotal, as it’s the unit that measures the amount of light falling on a surface. Solar lights are equipped with light-sensitive sensors that activate when the lux level drops below a certain threshold, usually under 45 on the lux scale.
  2. Battery Life and Sunlight Requirements: Another aspect to consider is the amount of sunlight needed for charging these solar devices. On average, 6 hours of sunlight is sufficient to keep a solar light operational for 8 to 9 hours. Even on cloudy days, these lights are designed to harness as much solar energy as possible, with some models featuring backup batteries that can last 2 to 3 days without sunlight.
  3. Troubleshooting Tips: Lastly, the article delves into common issues you might encounter, such as solar lights not turning on despite it being dark. Various solutions are offered, including checking the batteries, which usually have a lifespan of 1.5 to 2 years, and ensuring that no external light sources or shadows are affecting the sensors.

Do Solar Lights Come On Only When Dark?

Solar lights are a unique type of light that only turns on during the dark. They have special light-sensitive sensors to estimate whether or not it’s dark out. When the outside light level gets below a critical value, the sensors get activated and turn on the primary LEDs.

These lights cannot be activated when it’s bright out. They turn on automatically when it’s dark, and that’s the only control you have. You would trick it into turning on during the day, but the lights aren’t powerful enough to glow much during the daytime. 

How Dark Does It Need To Be For Solar Lights To Come On?

Solar lights turn on typically when it’s below 4 to 5 lux outside. Lux is a measure of illuminance that calculates the amount of light on a given surface.

During a moonlight night, the lux value is 1. But when there’s no moon, the outside lux is below 0.05. 

How Much Sun Do Solar Lights Need?

When buying solar lights, a typical concern is how much sun they need

The amount of required sunlight differs for each solar light. As a general estimate, around 6 hours and above is enough to charge the average solar light. With this, you can easily keep it running for about 8 to 9 hours during nighttime. 

But what happens when it’s cloudy out? Don’t worry — the batteries can salvage as much power from the sun as possible, even when it’s foggy outside. Manufacturers design some solar lights with a backup battery to run for at least 2 to 3 days without sunlight. You just have to ensure the light gets fully charged the day before to use this. 

Do Solar Lights Turn On In Shade? 

You might wonder if the shade is dark enough for solar lights to come on. Shades usually don’t have the critical lux value needed to turn on solar lights. But, they can still charge in the shade.

The charging speed and amount will be nowhere near efficient as in sunlight, but it works just fine. If you want to turn on solar lights in the shade, you can follow the first tips I’ve recommended in the next section.

What If My Brand New Solar Lights Are Not Working?

As solar lights are fully automated and require no human intervention, sometimes they get tricked and don’t work correctly. Let’s take a look at an example: it’s dark out, but your solar lights still haven’t turned on. 

To prevent issues like this from happening, let’s go over some tips that will help you.

  1. Block The Solar Panels

If an external light source is hitting your solar lights, tricking it into thinking it’s sunny out, you can simply block the solar panels. Doing this creates an artificially dark environment, which will make it think it’s nighttime. The lights should then come back on. You can use this to make solar lights work in the shade too. 

  1. Check The Batteries

When’s the last time you checked your solar light batteries? Although they’re rechargeable batteries with good-quality builds like Lithium-ion, they decay over time. The average lifespan of a solar light battery is around 1.5 to 2 years. If yours isn’t turning on, it might be time to get the batteries checked and possibly replaced.

  1. Avoid Shadows

Solar lights get tricked into thinking shadows as dim sunlight. To prevent this, ensure no shadows fall on your solar lights. Set them high in the sky where no buildings or lampposts may cast shadows. Doing this ensures they charge efficiently and turn on correctly when nighttime. 


If you came here not knowing how dark it needs to be for solar lights to turn on, you must be heading off with the proper knowledge. We’ve covered the basics of how they work along with the lux values of when solar lights turn on. 

As a final note, we’d recommend keeping animals such as squirrels away from your solar lights as much as possible. They might damage essential wires which handle the lux sensors. If this happens, your solar light won’t turn on even when it’s fully dark. 

Monitor your lights every 3 to 4 months, and you’ll be in the clear. Good luck!

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