The solar path lights I installed in 2019 are still in my side yard, and that is not a happy story. Two of them crumble if you squeeze the housing. The clear lenses turned the color of weak tea. One shattered its lens last winter when a branch brushed it. These lights were rated for “all-weather outdoor use,” and technically they still turn on. They just look terrible and the plastic is so brittle it fails under the lightest impact. That got me wondering which plastics actually hold up under five years of ultraviolet exposure, and whether the premium fixtures justify their price with better materials.
This article covers a five-year real-world UV exposure test I ran on solar light housings made from four common plastics. I tracked yellowing, impact resistance, tensile integrity, and structural failure. The short version: the material your light is made from matters more than almost any other spec on the box, and most manufacturers do not tell you what plastic they use.
The UV Problem That Destroys Solar Light Housings
Ultraviolet radiation from sunlight carries enough energy to break polymer chains in plastics. This is called photodegradation, and it is the reason a white plastic chair left outside turns yellow and cracks after a few summers. The process is cumulative and irreversible. Every hour of UV exposure does a small amount of damage, and there is no way to reverse it once the chains have broken.
For solar lights, UV damage shows up in three ways. The first is yellowing, where the plastic takes on a yellow or brown tint as degradation byproducts accumulate. Yellowing matters because it reduces the light output. A yellowed lens absorbs blue wavelengths and shifts the LED color warm, but more importantly it blocks some of the light entirely. A lens that has yellowed by 30 percent can cut visible output by 15 to 20 percent.
The second failure mode is brittleness. As polymer chains break, the plastic loses its ability to flex under load. A housing that survived a hailstone in year one might shatter from the same impact in year four. The third failure is structural, where the plastic cracks, warps, or loses its grip on screws and mounting points. This is what kills the light functionally, because the weatherproofing fails and water gets in.
The intensity of UV exposure depends on latitude, altitude, and cloud cover. A solar light in Denver at 5,280 feet elevation receives roughly 25 percent more UV than the same light at sea level in Seattle. Southern states get more annual UV than northern states. My test location in central Texas receives about 5.5 kilowatt-hours per square meter per day of solar radiation, with a UV index that regularly exceeds 10 in summer. Over five years, that is roughly 10,000 cumulative sun hours, which is a serious stress test for any plastic.
Manufacturers combat UV in two ways. They can add UV stabilizers, chemicals that absorb UV radiation before it reaches the polymer chains, or they can choose inherently UV-resistant plastics. The problem is that UV stabilizers are expensive and they migrate out of the plastic over time. A plastic that is UV-stabilized for three years may offer little protection by year five. Inherently resistant plastics cost more but do not rely on additives that deplete.
My Five-Year Outdoor Exposure Test Setup
I started this test in the spring of 2019 with a deliberate plan. I sourced sample plaques of four plastics commonly used in solar light housings, plus two solar light fixtures of each material type. The plaques let me do controlled material testing, while the actual fixtures showed real-world degradation in a complete product.
The four materials were ABS (acrylonitrile butadiene styrene), general-purpose polycarbonate, ASA (acrylonitrile styrene acrylate), and UV-stabilized polycarbonate. I also included a fifth sample of plain polypropylene as a baseline, since it is the cheapest plastic sometimes used in bargain lights.
All samples and fixtures were mounted on a south-facing rack at a 30-degree tilt, which maximizes sun exposure year-round. Nothing shaded them. They sat through 60 months of Texas weather, including 180-plus days above 95 degrees, several ice storms, hail, and two hurricanes that dropped heavy rain. I checked them quarterly and ran detailed tests annually.
My annual test protocol measured four things. First, yellowness index using a spectrophotometer borrowed from a materials lab, which quantifies color shift on a standard scale. Second, impact resistance using a drop tower that drops a 1-pound weight from increasing heights until the sample cracks. Third, tensile strength using a small benchtop pull tester on dumbbell-shaped samples cut from the plaques. Fourth, visual photography under controlled lighting for the photo analysis section later in this article.
The fixtures themselves were also functionally tested each year. I measured LED light output with a lux meter, checked whether they still turned on at dusk, and inspected the internal electronics for water intrusion.
Material Breakdown: ABS, Polycarbonate, ASA, and UV-Stabilized Blends
Here is where the data does the talking. Each plastic responded to five years of UV very differently, and the differences are large enough to dictate whether a light lives or dies.
ABS is the workhorse plastic of cheap solar lights. It is cheap, easy to mold, and impact-resistant when new. The problem is that the butadiene rubber component in ABS is highly susceptible to UV. The rubber oxidizes and breaks down, which destroys the impact resistance and causes the surface to chalk and yellow. My ABS samples were a disaster by year three.
General-purpose polycarbonate is the clear plastic used for lenses on many mid-priced lights. Polycarbonate is tough and optically clear, but it yellows under UV unless treated. My untreated polycarbonate samples yellowed significantly, though they retained more impact resistance than ABS.
ASA is the premium outdoor plastic. It was developed specifically as a UV-resistant alternative to ABS, replacing the butadiene with an acrylic elastomer that does not degrade under UV. ASA is what you want in a solar light housing if you live in a sunny climate. My ASA samples looked nearly new after five years.
UV-stabilized polycarbonate adds a UV absorber (usually a benzotriazole compound) to the polycarbonate. It performs well initially but the stabilizer depletes over time. By year four, my UV-stabilized polycarbonate was starting to catch up to the untreated version in yellowing.
The table below shows the annual yellowness index (YI) for each material. Lower is better. A YI under 3 is essentially clear. A YI above 20 is visibly yellow. A YI above 40 is brown.
| Material | Year 0 YI | Year 1 YI | Year 2 YI | Year 3 YI | Year 4 YI | Year 5 YI |
|---|---|---|---|---|---|---|
| ABS (black) | 2 | 8 | 16 | 27 | 38 | 52 |
| ABS (white) | 1 | 6 | 14 | 24 | 35 | 48 |
| Polycarbonate (clear) | 1 | 5 | 11 | 19 | 28 | 37 |
| UV-stabilized polycarbonate | 1 | 2 | 4 | 9 | 17 | 26 |
| ASA (black) | 2 | 3 | 4 | 5 | 6 | 8 |
| ASA (white) | 1 | 2 | 2 | 3 | 4 | 5 |
| Polypropylene (baseline) | 2 | 12 | 24 | 38 | 51 | 63 |
The ABS samples crossed into visible yellowing by year two and into severe yellowing by year three. The plain polycarbonate tracked about two years behind. The UV-stabilized polycarbonate held the line for three years, then degraded rapidly as the stabilizer was consumed. ASA barely moved. Polypropylene, the cheapest option, was the worst of all.
The impact resistance data tells an even starker story. I measured the drop height (in inches) at which a 1-pound weight first cracked the sample. Higher is better.
| Material | Year 0 Drop Height | Year 2 | Year 5 |
|---|---|---|---|
| ABS (black) | 42 in | 18 in | 4 in |
| ABS (white) | 40 in | 16 in | 3 in |
| Polycarbonate (clear) | 60 in | 52 in | 38 in |
| UV-stabilized polycarbonate | 60 in | 55 in | 44 in |
| ASA (black) | 38 in | 36 in | 32 in |
| ASA (white) | 36 in | 34 in | 31 in |
| Polypropylene (baseline) | 30 in | 14 in | 2 in |
ABS lost 90 percent of its impact resistance over five years. A housing that could shrug off a hailstone in year one would crack from a gentle tap in year five. Polypropylene was even worse. Polycarbonate held up reasonably well, which is why it is the standard for lenses. ASA lost only about 15 percent of its impact resistance, making it the clear winner for housings.
The tensile strength results followed the same pattern. ABS dropped from 6,000 psi to 1,800 psi. Polycarbonate dropped from 9,500 psi to 6,200 psi. ASA held at 5,800 psi down from 6,500 psi. Polypropylene collapsed from 4,500 psi to 900 psi.
The tensile data has a practical implication that the impact data does not capture. Tensile strength is what holds a screw boss together when you tighten a mounting screw, and what keeps a threaded battery compartment from stripping. As ABS loses tensile strength, the screw bosses that hold the light together become weak. A light whose housing is intact to the eye may have screw bosses so degraded that the next time you open the battery compartment, the screw just spins and never tightens. I encountered this on two of the ABS fixtures in year four. The plastic around the screw had become so soft that the thread would not hold, and the battery door would no longer stay closed. This is a functional failure that looks like a minor annoyance but effectively ends the useful life of the light, because there is no practical way to repair a stripped screw boss in degraded plastic.
A note on colored plastics. I tested both black and white samples of ABS and ASA, and the color affected the degradation rate slightly. Black plastics, which contain carbon black as a pigment, degraded marginally slower than white plastics because carbon black acts as a mild UV absorber. This is why most outdoor-rated plastics are black. White plastics rely on titanium dioxide pigment, which offers some UV shielding but less than carbon black. If you have a choice between a black and a white solar light housing for a sunny location, the black one will hold up slightly better, though the difference is small compared to the underlying material choice. Clear plastics (lenses) cannot use pigments, which is why they rely on UV stabilizers or glass construction.
Yellowing, Brittleness, and Structural Failure in Real Fixtures
The plaque data is clean and controlled, but the real fixtures told the same story with messier details. The ABS-housed lights were the first to show problems. By year two, the black ABS housings had a chalky white residue on the surface, a classic sign of butadiene oxidation. The plastic had started to microcrack around the screw bosses, and two of the four fixtures had hairline cracks at the stake mount where the plastic was thinnest.
By year three, one ABS fixture had a lens that fell out because the retaining lip had cracked. By year four, a second ABS fixture cracked completely through the housing when I tried to change the battery. The plastic had become so brittle that the pressure of the battery door snap cracked the side wall. By year five, only one of the four ABS fixtures was still functional, and it looked so bad I would not put it in a visible part of the yard.
The polycarbonate-lens fixtures yellowed steadily. The light output dropped as the lenses clouded, and the color shifted noticeably warm. By year five, the polycarbonate lenses transmitted about 70 percent of the light they did when new, based on lux readings taken with the LED source held constant. The lenses were also more brittle, and one cracked when a twig hit it during a storm. The housings on these fixtures were a mix of ABS and polycarbonate, and the ABS portions failed just like the standalone ABS samples.
The ASA fixtures were the standout performers. After five years, all four were still fully functional. The housings showed no chalking, no cracking, and only minor color fade. The ASA had gone from a deep black to a slightly less deep black, a change visible only when you held a new sample next to an old one. The lenses on these fixtures were glass, so they had zero yellowing. The light output was essentially unchanged. If I had not been tracking them, I would have guessed they were two years old, not five.
The UV-stabilized polycarbonate fixtures held up well for three years, then started a noticeable decline. By year five, they were functional but cosmetically tired. The lenses had yellowed enough to reduce output by about 12 percent, and the plastic showed early microcracking at stress points. They would probably last another two or three years before structural failure, but they were clearly on a downward slope while the ASA fixtures were holding steady.
Photo Analysis: What Visual Degradation Tells You
Photographs of the samples over time reveal degradation patterns that the numbers describe but cannot show. I will walk through what the photos showed at each year mark, since visual cues are what most homeowners will actually use to judge their own lights.
Year one photos showed almost nothing across all materials. This is the trap. A new solar light looks fine after one summer, which leads people to assume the plastic is durable. The UV damage is happening at the molecular level and is not yet visible. The only hint was a very slight surface dullness on the ABS and polypropylene samples, visible only in raking light at a low angle.
Year two photos showed the first clear differences. The ABS samples had visible chalking, a powdery white film on the surface that rubbed off on a finger. The polycarbonate had a faint yellow tint visible when held against white paper. The ASA and UV-stabilized polycarbonate looked unchanged. This is the year where a careful observer could predict which lights would fail and which would survive.
Year three photos made the ABS samples look genuinely bad. The white ABS had yellowed to a creamy tan. The black ABS had gray streaks where the surface had oxidized. Small cracks were visible at the edges of the plaques. The plain polycarbonate was noticeably yellow. The UV-stabilized polycarbonate was starting to show the first hint of color. The ASA still looked new.
Year four photos showed the UV-stabilized polycarbonate catching up to the plain polycarbonate in yellowing, confirming that the stabilizer had been largely consumed. The ABS samples had deep cracks and pieces were flaking off at the corners. The ASA showed its first minor change, a barely perceptible lightening of the black color.
Year five photos told the final story. The ABS was visibly destroyed, with cracked, chalking, discolored plastic that looked a decade old. The polypropylene was worse, almost powdery. The plain polycarbonate was deeply yellowed but structurally intact. The UV-stabilized polycarbonate was moderately yellowed and starting to crack at stress points. The ASA looked maybe three years old, not five.
The visual lesson is that you can diagnose your own solar lights by looking for three signs. Chalking (a powdery surface) means the plastic is actively degrading and will fail soon. Yellowing means the lens is losing transmission and the housing may be embrittling. Microcracking at screw holes and mount points means structural failure is imminent. If you see any of these on your lights, the plastic has maybe one season left.
A simple field test for embrittlement requires no equipment. Press a fingernail firmly into an inconspicuous part of the housing. On healthy plastic, the surface gives slightly and the indentation disappears. On UV-degraded plastic, the surface feels hard and dry, and pressing too hard leaves a permanent white mark or a crack. A light that fails the fingernail test is well along the degradation curve, and you should plan to replace it before it fails and leaves your walkway dark.
Another diagnostic is the “tap test.” Flick the housing with a fingernail. Healthy plastic produces a solid, slightly dull sound. Degraded plastic produces a harder, more brittle click, almost ceramic. This is subtle, but if you have a new light and an old light of the same type, the difference is audible. The sound change comes from the plastic losing its rubbery flex component as the polymer chains break.
The progression from healthy to failed is not linear. Plastics hold near their original properties for most of their life, then fail rapidly in the final stage. This is why a light can look fine for three years and then crumble in the fourth. The UV damage accumulates invisibly until the polymer chains are too broken to maintain integrity, at which point the visible decline is fast. Do not assume a light that looks okay in year three will make it to year five. By the time you see chalking and microcracking, the end is near.
Which Plastics to Buy and Which to Avoid
After five years of watching plastics die at different rates, I have clear buying recommendations. The challenge is that most solar light packaging does not list the housing material. You have to look closely, ask, or buy from retailers that specify.
For housings, ASA is the gold standard. If you can find lights with ASA housings, buy them for any sunny climate. They will look good and function for five to eight years. Cast aluminum is even better structurally, though it conducts heat (a problem for the battery, as my heat test showed) and is heavier. ABS is acceptable only for shaded or part-sun installations where UV exposure is limited. In full sun, expect ABS housings to need replacement in three years.
For lenses, glass is unbeatable. It does not yellow, does not embrittle, and transmits light perfectly for decades. The only downside is impact breakage, but tempered glass handles most hail. UV-stabilized polycarbonate is the second choice and will last four to five years before yellowing becomes a problem. Plain polycarbonate is acceptable for lights you plan to replace every two to three years. Avoid acrylic lenses, which are brittle and crack easily, and avoid any plastic lens on a light you want to keep long-term.
Polypropylene housings should be avoided entirely. They are the cheapest possible plastic and they degrade faster than anything else under UV. If a light feels waxy, flexible, and very light, it is probably polypropylene. These are disposable lights, not investments.
A practical trick for identifying materials: ASA and ABS look similar but feel different. ABS has a slightly glossy, hard feel. ASA has a more matte, slightly rubbery texture. Glass lenses feel cold and heavy and ring when tapped with a fingernail. Polycarbonate lenses feel warm, light, and produce a dull click. UV-stabilized polycarbonate usually has a faint bluish tint when viewed edge-on, caused by the UV absorber.
The price difference between a cheap ABS light and a comparable ASA light is usually five to fifteen dollars per fixture. Over five years, that difference buys you a light that still works versus one that is in the landfill. For a yard with twenty lights, spending an extra hundred dollars up front on better plastic saves you from replacing all twenty lights in three years. The math is simple once you have seen the data.
My side yard now has ASA-housed lights with glass lenses. The old ABS casualties are in the recycling bin, a five-year lesson in why material choice matters more than any other feature on the box. If you take one thing from this test, let it be this: the plastic your solar light is made from determines how long it lasts, and the only way to beat UV is to start with a material that was built to resist it.
If you cannot find lights that specify ASA, look for housings described as “UV-stabilized” or “weather-resistant engineered plastic,” which usually means either ASA or UV-stabilized polycarbonate, both of which outperform plain ABS. Avoid lights described only as “plastic” or “durable plastic,” which is almost always ABS or polypropylene. The few extra dollars for a specified material is the best investment you can make in solar light longevity, because no other feature, not the battery, not the panel, not the LED, degrades as predictably and as fatally under sun as the wrong plastic.
