How do solar lights turn on and off?

Illuminated Parking Lot - Solar Parking Lot LightsIt’s a simple question, but when you think about it a bit, the answer may just elude you. You may assume it is done automatically, but to really know what the underlying mechanism is, you need to understand how, for example, solar parking lot lights actually work.


If you have seen these fixtures before, you know that each individual light post has its own solar panel. What you may not have known is that each light post also has its own battery inside. So, during the day, the panel collects solar energy and transfers the electricity it has generated into the battery. The battery is regulated so that it cannot get overcharged. Naturally, charging is only possible during the day, when the sun reaches the panel. As the sun sets, fewer rays reach the panel and it generates less and less electricity until it finally stops.


During the night, the reverse process happens. All the collected electricity is slowly discharged by powering (usually) LED lights. The full charge that can be obtained from a single day of collecting can last for a few nights in case that charging is impossible or hindered. These situations occur when the weather is bad or the panel is damaged in some way.

How do LEDs know when to switch on?

The most common assumption people make is that the lights turn on at predetermined times at dusk, and turn off at a predetermined time at dawn. However, this system would require a lot of maintenance. During the year, dusk and dawn come at different times, so that would have to be accounted for. Additionally, if the area uses daylight time saving, the amount of work would just pile up. But most of all, this system is not used because it does not account for foggy, cloudy or otherwise poorly visible days. The preset timer wouldn’t switch on the much-needed lights in these detrimental conditions.

If not timing, then what?

The design of the solar parking lot lights is actually quite brilliant. The battery sensor measures the input of electricity it gets from the panel. When this input drops under a certain level, the lights turn on. The panel still inputs energy into the battery, even as it is beginning to slowly discharge. This is the ideal preset if you think about it a bit.

If the panel is unable to get enough light, it means that there isn’t enough light, so the lamps need to be switched on, regardless of the time of day. And vice versa, once the panel starts producing enough energy, usually at dawn, the lights turn off, making this the most energy effective method of light management.

New developments

Despite being brilliant and very energy efficient, this is not the only method used in modern solar lighting. If you want to be even more energy efficient, you can switch off the lights during the hours that see little to no activity, such as the hours after midnight, and before 5 AM. The system is adaptable, and can be timed manually, or left to calculate the optimal times to turn off on its own. This way, these lights can be more compact and energy efficient, and that usually translates into financial savings as well.

Greenshine Solar Power is a company with a decade-long experience in building and installing solar fixtures for a multitude of purposes, both for personal and industrial use. Contact Greenshine if you need further information about solar lighting.