I live and work in a climate where the ground freezes solid by December and does not thaw until April. Winter here is not a season of reduced performance for solar lights. It is a season of destruction. A light that survived summer and fall can be destroyed by a single January freeze-thaw cycle, or buried under snow until spring, or cracked by ice expansion in a gasket joint that was fine in October.
Winterizing solar lights is not optional in cold climates. It is the difference between fixtures you use for five years and fixtures you replace every spring. This guide covers the decisions, the process, and the timing, based on fifteen years of installing and maintaining solar lights in a region where the temperature drops below zero.
The First Decision: In or Out
Not every solar light needs to come inside for winter. Some can stay out and function, with caveats. The decision depends on the fixture type, the climate severity, and whether you want the light to operate through the winter.
Lights That Should Come Inside
String lights. The wire becomes brittle in cold and snaps at the connection points. The bulbs crack if ice forms on them. Bring string lights in.
Decorative figurine lights. Plastic and resin figures become brittle in cold and crack under snow load. Bring them in.
Tabletop and portable lanterns. These are designed to be moved. Bring them in. There is no reason to leave a portable light out in a blizzard.
Cheap path lights with plastic stakes. The plastic stakes snap in frozen ground, and the fixtures themselves may crack. If the light was under $10, bring it in. It is not worth the risk.
Lights with NiCd batteries. NiCd batteries perform poorly in cold and may be damaged by freezing. If the light uses NiCd, bring it in, or at least remove the battery.
Lights That Can Stay Out
Post cap lights on deck or fence posts. These are mounted permanently and designed for outdoor use. They can stay out, but remove the batteries to prevent cold damage and corrosion.
Wall-mounted sconces and security lights. Permanently mounted, weather-rated fixtures can stay out. Remove batteries if possible.
In-ground well lights. These are buried and cannot be easily removed. They stay out. Ensure the lens is clean and the gasket is sealed before winter.
Premium path lights with metal stakes. Metal stakes do not snap, and metal fixtures do not crack. These can stay out, with batteries removed.
Spotlights with remote panels. The fixture and panel can stay out. Remove the battery from the fixture if accessible.
The Operating Question
The second question, after whether the light can physically survive, is whether you want it to operate through the winter. Winter solar lighting is challenging because the days are short, the sun is low, and snow covers the panels. Even a well-winterized light may not perform well in deep winter.
If you want winter operation, the light stays out, with batteries installed, and you accept reduced performance. If you do not need winter operation, bring the light in or remove the battery. A light without a battery is not damaged by cold, because there is no chemistry to degrade.
The Winterization Process
Step 1: Clean Everything
Before you do anything else, clean every fixture. A clean light entering storage does not corrode. A dirty light, with dust and moisture on the panel and lens, corrodes over winter even in storage.
Wipe the solar panel with a damp microfiber cloth. Clean the lens. Wipe the housing. Let everything dry completely before proceeding.
Step 2: Remove Batteries
This is the single most important step. Batteries left in fixtures over winter are the number one cause of spring failure.
Cold damages batteries in two ways. First, the cold itself degrades the battery chemistry, reducing capacity permanently. Second, if any moisture has entered the battery compartment, the moisture freezes and expands, cracking the battery case or pushing the contacts apart. A battery that freezes with moisture around it may leak, and the leaking electrolyte corrodes the contacts and the circuit board.
Remove every battery. Label it with the fixture it came from, using a piece of tape. Store the batteries in a cool, dry place indoors, in a plastic container. A basement or a closet is fine. Do not store batteries in a freezing garage.
Store batteries at about 40 percent charge, not fully charged and not dead. A battery stored fully charged degrades faster. A battery stored dead may not recover. If you cannot measure the charge, store the batteries after a few days of no sun, which leaves them at a moderate charge.
Step 3: Inspect and Repair
With the batteries out, inspect each fixture for damage that will worsen over winter.
Check the gaskets. A cracked gasket lets moisture in. Replace any cracked gasket before storage, because the repair is easier now than in spring when you want to use the light.
Check the housing for cracks. A cracked housing lets water into the electronics. Repair small cracks with silicone adhesive. A heavily cracked fixture is a candidate for replacement, not repair.
Check the stakes and mounts. Straighten bent stakes. Tighten loose screws. A fixture that goes into storage in good condition comes out in spring in good condition.
Check the wire connections on remote panel fixtures. A loose connection corrodes over winter. Re-solder or re-crimp any questionable connections.
Step 4: Store or Seal
For lights coming inside, store them in a dry, rodent-free location. Rodents chew wires, and a light stored in a shed may be destroyed by mice over winter. A plastic storage tote with a lid keeps rodents out and keeps dust off.
Do not stack heavy items on top of stored lights. The lenses and panels can crack under weight.
For lights staying outside, seal the battery compartment. With the battery removed, the compartment is an empty space that can collect moisture. Place a small packet of silica gel desiccant in the compartment to absorb moisture. Close and screw down the compartment cover. Apply a bead of silicone caulk around the cover if the gasket is marginal.
Step 5: Protect Panels From Snow
For lights staying out, the solar panel will be covered by snow at some point. A snow-covered panel charges nothing, and the weight of snow can crack a panel.
Panel Covers
The simplest protection is a cover over the panel. A piece of canvas, a plastic bag, or a purpose-made cover keeps snow off the panel. The cover means the light does not charge, but if you removed the battery, the light is not operating anyway, and charging is irrelevant.
Remove the cover in spring when the snow season ends, so the panel can charge again.
Panel Orientation
If you have an adjustable panel, tilt it to a steep angle, 60 degrees or more, before winter. A steep panel sheds snow, because the snow slides off rather than accumulating. A flat panel collects snow and stays covered.
A steep panel also catches the low winter sun better, if you are trying to keep the light operating. The winter sun is low on the horizon, and a steep panel is perpendicular to it.
Brushing Snow
If you want the light to operate in winter, brush the snow off the panel after each storm. Use a soft broom or a brush, not a shovel, which will scratch the panel. Brush gently, because cold plastic panels are brittle and crack under impact.
Do not use salt or de-icer on the panel. The chemicals damage the panel surface and corrode the housing.
Cold Climate Battery Science
Understanding what cold does to batteries helps you make decisions about which batteries to use and how to store them.
NiMH in Cold
NiMH batteries lose capacity in cold, but they recover when warmed. A NiMH battery at 32 degrees might have 70 percent of its room-temperature capacity. At 0 degrees, it might have 40 percent. This is temporary. Warm the battery up and it works normally.
However, if a NiMH battery freezes, the electrolyte can expand and crack the case. A fully charged NiMH battery freezes at about minus 40, but a discharged battery freezes at a warmer temperature, around minus 4. This is why you should not leave discharged batteries in a fixture over winter.
Li-ion in Cold
Li-ion batteries also lose capacity in cold, and they cannot be charged below freezing without damage. If a solar panel tries to charge a frozen Li-ion battery, lithium plating occurs on the anode, which permanently reduces capacity and can create a short-circuit risk.
For this reason, any solar light with a Li-ion battery should have the battery removed for winter in a cold climate. The panel will still produce voltage, and without the battery to absorb it, the charge controller may be damaged. Removing the battery breaks the circuit and protects the controller.
Storage Temperature
The ideal storage temperature for both NiMH and Li-ion batteries is 40 to 60 degrees. A basement is usually in this range. A refrigerator is too cold and too humid. A freezer is destructive. An attic is too warm and too variable.
Store batteries in a plastic container, not loose. Loose batteries can contact each other and short circuit. A battery holder, the kind with individual slots, is ideal.
Which Fixtures Survive Winter Best
If you are shopping for solar lights for a cold climate, choose fixtures that are built for it.
Metal Housings
Cast aluminum and stainless steel survive cold better than plastic. Metal does not become brittle in cold. It does not crack under snow load. It does not shatter when hit by a snow shovel.
Plastic housings, especially cheap polycarbonate, become brittle below 20 degrees. A plastic fixture that survives summer may crack in winter from nothing more than thermal contraction.
Glass Lenses
Glass survives cold fine. It does not become brittle. It does not yellow. It does not crack from temperature changes, unless the change is extreme and sudden.
Plastic lenses become brittle in cold and can crack. If you have a choice, choose glass.
Silicone Gaskets
Silicone remains flexible at low temperatures. Rubber hardens and cracks. A silicone gasket maintains its seal through winter. A rubber gasket may fail.
Check the gasket material before buying. If the manufacturer does not specify, assume rubber, which is the cheaper material.
Replaceable Batteries
A fixture with a replaceable battery is winterizable, because you can remove the battery. A fixture with a sealed, non-replaceable battery cannot be winterized, because the battery stays in the fixture whether you want it to or not.
For cold climates, avoid fixtures with sealed batteries. They will fail after one or two winters, and you cannot prevent it.
The Spring Re-Installation
Winterizing is half the job. The other half is bringing the lights back in spring.
Timing
Wait until the danger of hard freeze has passed. In most cold climates, this is late April or early May. Bringing lights out too early risks a late freeze that can damage a battery or crack a moisture-filled housing.
Check the forecast for a week of above-freezing nights before you re-install.
Inspect Before Installing
Before you put a light back in the yard, inspect it. Look for cracks that developed in storage. Check the gasket. Test the battery with a multimeter or by installing it and checking for operation.
A light that was fine when stored may have developed issues. A rodent may have chewed a wire. A gasket may have dried out. Catch these before installation, not after.
Charge Before Use
Install the battery and place the light in the sun for 2 to 3 days before the first night of use. The battery has been sitting all winter at partial charge and may have self-discharged significantly. A full charge before the first use conditions the battery and ensures the light operates correctly from the first night.
Re-Position
Check the position of each light. Frost heave may have pushed stakes up. Snow may have bent mounts. The planting may have changed. Re-position as needed, following the same principles as the original installation.
A Winterization Checklist
Run through this list for every fixture:
- Clean the panel, lens, and housing
- Remove the battery, label it, and store it indoors
- Inspect gaskets and replace if cracked
- Inspect housing and repair cracks
- Inspect wires and connections
- For stored lights: pack in a dry, rodent-proof container
- For outdoor lights: add desiccant to the battery compartment, seal the cover
- For outdoor lights: tilt panels steep, or cover them
- For outdoor lights: remove snow after each storm if operating
Do this every fall, before the first hard freeze, and your solar lights will last years longer than they would if left to fend for themselves.
Common Winterization Mistakes
Leaving batteries in. This is the big one. Batteries left in fixtures freeze, leak, and corrode the contacts. Remove every battery, every fall.
Storing lights dirty. Dust and moisture on a stored light corrodes the panel and the contacts over winter. Clean before storing.
Storing in a freezing location. A shed or garage that drops below freezing is not suitable storage. The fixtures may survive, but the temperature cycling stresses every component. Store indoors.
Forgetting where things go. If you have many lights, label each one with its location before storing. In spring, you will not remember which path light went at the corner and which went by the gate. Labeling saves hours of re-arranging.
Not checking in spring. A light that goes into storage in good condition may not come out in good condition. Check before installing.
Trying to operate lights in deep winter. The days are short, the sun is weak, and the panels are snow-covered. Accept that solar lights do not work well in January, and plan for it. Do not expect reliable winter operation, and do not be disappointed when you do not get it.
Regional Variations in Winter Severity
Not all cold climates are the same, and the winterization process should match your specific conditions.
The Dry Freeze Zone
In high-altitude climates like the Rocky Mountain West, winters are cold but dry. Snow falls and stays, but there is little freeze-thaw cycling because the temperature stays below freezing for months. This is actually gentler on solar lights than a wet climate, because there is no liquid water to infiltrate fixtures and crack them when it refreezes.
In the dry freeze zone, the main risks are UV damage from the intense high-altitude sun reflecting off snow, and physical damage from snow load. Panels can be covered, and fixtures that stay out need only battery removal and desiccant. The dry air means corrosion is slow.
The Wet Freeze Zone
In the Northeast and Midwest, winters feature repeated freeze-thaw cycles. A warm day melts snow, water seeps into every crack and gasket, and the next cold night freezes it solid. This cycle is destructive to solar lights, because the ice expansion forces joints apart and cracks housings.
In the wet freeze zone, sealing is critical. Every gasket must be intact, every screw hole must be caulked, every battery compartment must be desiccated. Lights that stay out need more attention than in the dry freeze zone, and more lights should be brought inside.
The Coastal Cold Zone
In coastal New England and the Pacific Northwest coast, cold is accompanied by salt air and driving rain. Salt corrodes metal fixtures and electrical contacts faster than fresh water. Wind storms are frequent and severe.
In the coastal cold zone, bring everything inside that you can. For lights that stay out, apply a corrosion inhibitor spray to the battery contacts before sealing the compartment. Check fixtures in early spring for salt damage, because the corrosion may not be visible until the weather warms.
The Brief Freeze Zone
In the South and parts of the Southwest, freezes are brief and unpredictable. A cold night drops below freezing, the next day is warm. Solar lights in these climates do not need full winterization, but they do need attention before the first forecast freeze.
Remove batteries from any fixture that might be exposed to a hard freeze, even if you put them back the next day. A single freeze can damage a battery if it is discharged. The brief freeze zone is actually riskier for batteries than a sustained cold climate, because people do not expect the freeze and do not prepare.
Final Thoughts
Winterizing solar lights is unglamorous, time-consuming work. It is the kind of maintenance task that is easy to put off and easy to skip. But if you live in a cold climate, it is the single most important thing you can do to protect your investment.
The process is the same every year. Clean, remove batteries, inspect, store or seal. It takes an afternoon for a typical yard. And every spring, when your lights come out of storage and work on the first night, you will be glad you spent the time. The alternative is a spring of replacing fixtures that could have survived, and a summer of wondering why your lights never seem to last.
