The ultimate guide to interpreting solar lighting spec sheets

 

If you're planning to use solar lighting for your next project, you're on the right track. But before you jump into buying, there's something crucial you need to understand: how to read and interpret a solar lighting specification sheet.

 

Unlike other consumer products like air fryers or smartwatches, solar lighting doesn’t have a one-size-fits-all guide. There’s no Wirecutter or CNET to tell you which product is best. Instead, you’ll be relying on spec sheets—documents that hold all the technical details needed to make an informed decision.

 

A spec sheet is more than just a list of numbers. It's a blueprint of what a product can do, and it's essential when comparing different manufacturers. But if you don't know what to look for, it can feel overwhelming. That’s why we’re here—to help you decode the language of solar specs and avoid common pitfalls.

 

The Key Information You Need

 

While spec sheets are packed with technical data, not all of it is relevant to your project. The most important four pieces of information to focus on are:

1. Solar panel size (in watt-peak – Wp)
2. Fixture output (in watts – W)
3. Battery capacity (in watt-hours – Wh)
4. Operating profile or run-time (how long the system needs to run at a given light level)

These will determine whether the system can meet your energy needs. If any of these are missing from a spec sheet, it might be a red flag—especially if the manufacturer is reluctant to provide clear details.

 

Here’s an example of a well-documented spec sheet with key elements highlighted:

 

With this data, you can perform basic calculations to check if the system meets your requirements.

 

Solar Panel Sizing

 

To determine the right size of the solar panel, start by finding the average peak sun hours in your location during the worst month. The NREL PVWatts Calculator is a great tool for this.

 

For example, in Charlotte, NC, peak sun hours in December are about 3.73. Multiply that by the panel size (in Wp) to get the daily charging capacity.

3.73 x 110Wp = 410Wh

 

But remember, peak sun hours vary. To ensure reliability, use an array-to-load ratio (ALR) of 1.2:1 to account for less-than-ideal conditions.

410 / 1.2 = 341Wh

 

Ignoring this step could lead to failure during low-sun months. Reputable manufacturers also apply derating factors to account for dust, shade, and temperature—so always ask about them.

 

Fixture Output and Operating Profile

 

Next, calculate how much energy the fixture will consume. Use NOAA’s Solar Calculator to find the longest night. For Charlotte, that’s around 14 hours.

 

Then, refer to the spec sheet for the fixture’s output. Suppose it’s 30W. Multiply that by the number of hours to get the daily load:

30W x 14 = 420Wh

 

This means the solar panel must generate enough energy to recharge the system each day. If it doesn’t, consider adjusting the operating profile—like dimming the lights in the middle of the night.

 

For instance, a 4D1 profile would reduce power usage significantly, making the system more efficient and sustainable.

 

Battery Capacity and Chemistry

 

Batteries are the backbone of a solar lighting system. They determine how long the system can operate without sunlight. A good rule of thumb is to have enough battery capacity to last two full nights.

 

Using our previous example:

285Wh x 2 = 570Wh

 

But batteries shouldn’t be fully discharged. Lead-acid batteries should only be used up to 25%, while lithium batteries can go up to 70%. Adjust your calculation accordingly:

570Wh / 0.7 = 814Wh

 

Some manufacturers ignore these limits, leading to undersized systems that fail quickly. Always verify the depth of discharge (DOD) and battery chemistry.

 

Other Important Factors

 

Warranty

Even with grants, solar lighting is a big investment. A strong warranty gives you peace of mind. Look for full coverage on the system, including the battery.

 

Certifications and Testing

Certifications like IEC or IEEE ensure the product meets industry standards. LM-79 testing is especially important as it verifies the actual performance of the entire fixture—not just the LED chip.

 

Fixture Quality

Where the fixture comes from matters. Some manufacturers build their own, while others use third-party components. High-quality fixtures from trusted brands like Acuity Brands offer better performance, longer lifespan, and superior light quality.

 

Final Thoughts

Understanding solar lighting spec sheets isn’t easy, but it’s doable with the right knowledge. By focusing on the right metrics and asking the right questions, you can choose a system that fits your project perfectly.

 

Have questions? Our team of solar lighting experts is here to help. Let’s find the best solution for your needs.