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Educational May 2019

The Science of Sizing

How a properly sized solar lighting system ensures reliability, efficiency, and cost-effectiveness

At Sol, our philosophy is to provide a solar light that operates like a regular street light—meaning that we don’t dim the lights in bad weather to make sure we don’t kill the battery. Instead, we properly size our solar lighting systems for each location to ensure we have the right amount of solar and battery capacity. This means the EverGen light will maintain the same light levels as a grid-tied light and be reliable throughout the year in all weather conditions—when you need it most! Our infographic shows how we do it.


Download the infographic as a printable PDF

Energy in must equal energy out.

Energy in! It’s the energy collected and stored within the batteries.

  • The sun’s energy generates power (even when it’s cloudy). Summer = more energy generated. Winter = less energy generated.
  • The solar panel collects and converts the sun’s energy into DC power.
  • The energy management system (EMS) regulate and maximize the flow of power to the battery.
  • The battery stores the DC power during the day until it’s needed at night.

Energy out! It’s the energy required to run your light. (Even when the weather is poor.)

  • The EMS prevents power loss when it transfers the right amount of power from the battery to the fixture, turning it on and off as intended.
  • The LED fixture turns on and provides light where and when you need it.

How do you know if a system has been properly sized?

It’s easy to tell if a system is NOT properly sized: the battery will die prematurely. That means that the components are not properly configured to work together sustainably over the long term.


Here’s how we make sure that doesn’t happen.


Location, location, location: Any reputable manufacturer should factor in the location of your lights when sizing your solar light. We use data from NASA and NREL to measure the solar energy available in your location in the wintertime. This is called solar insolation—AKA equivalent sun hours or peak sun hours.


Solar panel sizing: We ensure that energy in exceeds energy out. This should be achieved by selecting panels of an appropriate wattage for the sun hours in the light’s location. Be wary of manufacturers that overcompensate by adding more or physically larger panels in an attempt to improve the system’s ability to collect energy.


LED fixture selection: Solar lighting systems use LED fixtures because they are the most energy-efficient light fixtures available. Today’s LEDs have higher efficacy, meaning they can provide more units of light (lumens) with less energy (watts). The amount of power available at night to do so is limited by the capabilities of the battery storage.


Batteries that work: Many people believe solar powered devices don’t work because their batteries die too quickly. But this doesn’t mean the technology is faulty or unreliable: instead, it means that the system was improperly designed. There are several types of batteries, including lead acid and lithium ion, but no matter what type you choose, it should have enough power collection and storage capacity to ensure the system can sustain the light levels you require while being properly factored into the sizing equation. The size and amount of battery storage needed depend on customer needs, as well as the light intensity requirements in the location.


A team of experts: We used our extensive human experience to build a sizing engine that calculates the location data mentioned above against our own engineered components’ performance. This means we clearly understand exactly how our system will perform in your location—and to your standards.

Read more Sol articles

The Future of Solar is Bright: The Top Three Things We Learned at SALC 2023

Sunna Design Lights the Way: Achieving New Milestones in 2023

Sol exhibited at Light Fair 2023

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