Solar-Powered Landscape Lighting Needs an Eco-Makeover (and Fast)
Although inexpensive, these short-lived products are creating mountains of e-waste and hard-to-recycle plastic.
They seem to be everywhere, for three or four bucks each. From Walmart to Lowes, Dollar Stores to Amazon, small solar-powered landscape lights have become the twinkling stars of many gardens and pathways. Now, we can all light up our homes and yards at night like the McMansions of the affluent.
But these products are not “green,” whatever the word “solar” might suggest. They’re bordering on “throw away” products in terms of design and materials. So what happened? How did they become so endemic? Maybe it’s the popularity of aspirational home shows on TV, where people live in palatial properties and never seem to worry about utility bills. Landscapers attribute their rise in part to Covid-19 shut-ins of recent years.
Let's dive into three big problems with these shiny toys for our gardens and walkways.
1. Plastic and Sun Don’t Mix
Little research has been done on the environmental footprints of solar yard lights. So I’ll do my best to piece together what they’re made of, how long they last, and where they end up. I hope this article will excite some PhD student somewhere to do a more thorough lab analysis.
Most solar lights feature polymer-coated solar panels. As any material scientist will confirm, however, polymers degrade under UV light. Although stabilizers can help, most will ultimately turn hazy, yellow and brittle - a process similar to how a paperback book cover curls and fades in the sun.
Material research shows that UV breaks down polymers quite quickly. Image Source
Ultimately what this means is that these mini panels simply don’t last. How long before they fail? That’s a function of the climate they’re used in, whether they’re left out year round, and how many hours of sun they get. But in my anecdotal experience using several different brands in the Florida sun, most die within a year. A few linger on for 2-3 years.
After two years of Florida sun, this plastic pv panel has become both inoperative and unrecognizable, past the point of no return.
It’s possible to rehabilitate the solar panels on some solar lights, as this video shows, if you catch them before the UV damage is too severe, and extend the panel life (but not the battery life). What you’re doing is essentially replacing the polymer coating with a clear acrylic paint.
2. Batteries are Toxic and Wimpy
Solar landscape lights typically use Nickel-Metal Hydride (NiMH) or Nickel-Cadmium (NiCd) batteries. Neither has exceptional longevity. NiMH are considered less toxic in terms of disposal at end of life. NiCd contain heavy metals that can easily end up in landfills or incinerated to pollute our atmosphere.
NiCd batteries, as this industry source notes, will survive 1 or 2 years, depending on conditions. NiMH may last longer, depending on weather conditions, but in my experience, both types tend to provide disappointing performance. Within a few months, they seem to hold their charge for shorter duration, then ultimately stop firing up the LED solar light at all. Whether this poor showing results from panel degradation, battery failure, or both, is a topic for future research.
The end result is that these batteries have about the same life expectancy as the plastic-shielded solar panels. They’re likely to end up in the waste stream together.
3. Solar Lights are Hard to Recycle
Solar lights are simple devices, but they’re just a little too complicated for easy recycling. They contain circuit boards, batteries and LED lights.
This means that the plastic cases, posts and stakes are unlikely to be recycled, because they must first be disassembled. The solar assembly has to be broken into its disparate parts, some of it sent to an e-waste facility. And of course, some of the batteries also need e-waste handling.
Another problem with these products is that they’re vulnerable to lawn equipment. Lawn mowers and weed whackers can send splinters of plastic in every direction. At that point, most homeowners will just toss all components into the nearest trash can.
A Low-Voltage Workaround?
Historically, owners of higher end homes tend to opt for low-voltage landscape lights to improve curb appeal. But given the waste and lack of durability of low-budget solar lamps, low-voltage products deserve a second look. For those who really want the flashy look of night lighting, it’s possible to combine better solar and storage with lighting and create a more durable system.
For example, here’s an example of using a single glass solar module with a single battery to power about 20 solar lights. I installed one myself recently.
My “kit” of 10 low-voltage lights came with 5 watt incandescent bulbs with only a 500 hour lifespan. I immediately ordered 2-watt LED replacement bulbs with a lifespan of at least 15,000 hours each.
This low-voltage alternative provides a much brighter and more reliable type of lighting, with a much longer potential lifespan.
The kit came with a big, clunky 12V transformer. In hindsight I didn’t need it and should have ordered just the lights.
I did some calculating and found that a single 100Ah battery would provide me with 40 watts of power for 30 hours. That would leave enough “slack” in the storage that it could continue to run the lights for three full nights after just one day of sunlight. A 100-watt solar panel charge the battery fully in about 12 hours.
Adding up the costs of my low-voltage set-up, I spent two to three times what I would have for solar lights, but it should last up to 20 years (ten times longer than a lot of solar lights), if I don’t destroy it with a lawn mower.
Which Way Forward?
Solar light makers could adjust their manufacturing practices to improve these poor-performing products. PV panels could be coated with materials resistant to sun damage. They could install more durable batteries with “takeback” recycling programs, and significantly improve the lifespan and environmental impact of solar-powered landscape lights. In the meantime, if outdoor lighting is on the priority list, low-voltage systems with solar power banks make sense.
It’s time that we started taking outdoor lighting more seriously. It’s verging on crossing over from a fad to another ecological menace. A lot has been written on the impacts of night lighting on wildlife and sky gazing, but precious little on its other environmental costs.
Fact Check: “Glass” Solar Landscape Products Have the Same Issues
You may find reference to “glass” solar lights. This refers to the lamp casing, not the solar panel. I wasn’t able to find a single landscape light with a glass-shielded PV panel, so please write me if you identify one. Even slightly pricier products with glass and stainless parts appear to have plastic PV panels. I suspect economics drives this decision. Small, thin sheets of glass would be fragile to transport and increase the cost of the race to the price bottom of “commodity” lights.