Solar LED Christmas lights
Sounds green, sounds fun - but do these lights really work?
This morning my wife was shopping for solar LED Christmas lights. Dusk is falling earlier now, Christmas is around the corner, and if you're going to get new Christmas lights, why not go off the grid at the same time?
We have regular LED Christmas lights tucked away in a storage box, so I asked why we needed more. Considering I own an energy efficiency website, she teased me, I ought to be into buying solar powered lights instead of the plug-in kind.
But that got me to thinking: are the energy savings from solar LED Christmas lights enough to justify the environmental costs of manufacturing them? And is the quality of solar LED Christmas lights good enough that you'll want to keep them, and not wind up throwing them in the trash before their first season is out?
With that in mind, I did a little research, and found that, while the idea sounds green and sounds kind of fun, there are a lot of solar LED Christmas lights out there that don't work that well, or don't last long; a few that have satisfied most of their purchasers; and little in the way of either economic or environmental benefits to justify replacing regular LED Christmas lights with solar ones.
Let's look at some of the main issues affecting the suitability of these lights to typical household use. Here's what I cover:
Light output
One thing people tend not to realize when shopping for solar LED Christmas lights online is how tiny many of the actual lightbulbs are. The tiny solar panels that are used to charge these lights are typically made with the lowest grade of solar cells - those unfit for use in actual solar panel arrays used to power an off-grid home, for example. So right off the bat you're not getting much amperage from the solar cells. On top of that, since Christmas occurs at the darkest time of year for people in the temperate parts of the Northern Hemisphere, you're not going to get that much sunlight to charge your lights, although if you're looking to use the lights to brighten a patio on a summer evening that is less of an issue. Nonetheless, most of these solar LED Christmas lights have so little light output that you can't use them to light a patio or walkway to the point where you can see. Think of it as the difference between a full moon - which provides enough light to walk through a meadow at night - and a moonless night full of stars. The LEDs used in solar LED Christmas lights tend to be more like stars than a full moon. Pretty to look at, but tiny and dim.
Plug-in LED Christmas lights, on the other hand, range from moderate to very high light output. Most bulbs have wattages from 0.15 to 1 watt, with a 1-watt bulb being very bright, considering it is an LED. (I have a 1.2 watt GU10 bulb in my basement that replaced a 50-watt halogen bulb!) There's just no comparing the light output of these solar-powered LEDs to the plug-in LED Christmas lights that have been on the market for several years now.
Also note that the white LED lights sold with solar chargers tend to have a bluish tint, which is normal for white LED's. Although you can get plug-in white LEDs that have a softer, more yellowish white light, the ones currently sold as solar-charged white LEDs tend to be that more bluish tint (closer to natural daylight, in fact, but humans are used to the more yellowish tint of candles and incandescent lights, and so prefer that).
If you just want to be able to look out into your yard and see some pretty sparkling points of light, solar LED Christmas lights might be what you're after. If you want a brilliant display, or enough light to help you find your way down a garden path, or see the person sitting across from you on a summer night on the patio, you'll need something a little more powerful!
Temperature issues
Solar LED Christmas lights typically charge up a battery during daylight, and then, when they detect there's no more light, turn on the LEDs, which shine until the battery is drawn down to empty.
One problem with using batteries for outdoor lighting in winter is that cold temperatures reduce both the charge rate and the capacity of battieries. Most batteries need to be brought up to temperatures above the freezing point in order to charge efficiently (inefficient charging means that much of the energy being generated by the solar cell doesn't actually make it into the battery). Nickel cadmium (NiCad) batteries can be recharged at below freezing. Lithium ion batteries and nickel metal hydride (NiMH) batteries generally cease to function at -20C, while NiCad batteries can go down to -40C; some newer Lithium Ion batteries can go down to -40C. In any event the charge rate for all batteries is very slow in cold temperatures, and the ability to draw power is also reduced.
In Toronto where I live, it doesn't usually dip below -5C around Christmas, but it can get as cold as -20C in January and February, especially at night, which means even if it was warm enough during the day for the battery to charge, it may be too cold at night for any of that charge to effectively power the LEDs.
The result is that your solar LED Christmas lights may not provide light for very long each evening before the battery is discharged and shuts the lights off. And many of the cheaper products come with substandard batteries that are likely to fail within weeks of purchase; many buyers report having to buy a new rechargeable NiCad within the first season. This is one of the hidden costs you need to factor into solar LED Christmas lights that you don't need to worry about with plug-in lights.
Another issue with cold weather is that extreme cold can make some forms of plastic go brittle (so can UV radiation from sunlight). The more cheaply made solar LED Christmas lights have poor-quality plastic sheathing on their wires, and consumers in colder regions have reported cracked or peeling wiring within the first winter of use.
You might think you can solve all this by using the lights indoors instead of out. Place your charger on the inside of a south-facing window, and use the solar LED Christmas lights to light up your Christmas tree or the window frame. This will take care of both the battery temperature sensitivity and the brittle wiring issue. Unfortunately, the glass from your window will reduce the photovoltaic output of the solar charger somewhat, especially if you have a low-e coating on the glass.
Moisture issues
You would think that solar LED Christmas lights would be designed to withstand not only cold temperatures but moisture. But there are many reports of the battery casings for these units not being properly sealed against rain and other moisture sources. As a result moisture builds up inside the casing, damaging the batteries or preventing a proper contact with the terminals, so the charge and discharge rates are reduced.
This may not happen right away. In some cases it seems the same factors that affect wiring brittleness are affecting the plastic battery casing: sunlight and cold temperatures. This isn't rocket science: it should be easy to make a sturdy, waterproof casing that withstands cold. But the cheaper solar LED Christmas lights have skipped that step!
Environmental impact
Many people look for solar LED Christmas lights in the misguided notion that anything solar-powered must be environmentally friendly. Given the concerns I've raised above with light output, low-quality solar cells, charging capacity on cold days, poor battery quality, and poor construction of the battery casing, one of the things you should ask yourself is whether the fact that you're using solar power instead of electricity from the grid is enough of an environmental benefit to offset the non-solar energy that was used in the resource extraction of the raw materials, the manufacture of the components, and the energy required to dispose of the solar LED Christmas lights if you decide, as many purchasers have, that they aren't bright enough, don't last long (due to dying batteries or corroding battery cases or broken, brittle wires), or don't work well in cold weather. There's no environmental benefit to buying a 'green' product that you then just throw out.
Let me shed a little light on the demand side of this equation: if you're hoping to save energy by buying solar LED Christmas lights instead of plug-in lights, there really isn't that much energy there to save. A couple of years ago I bought a 50-bulb, plug-in string of (very bright) LED Christmas lights and plugged them into my Kill A Watt meter, which measures, among other things, wattage of a device, and kilowatt hours consumed by the device over time. Unfortunately the meter only registers demand in whole watts, and the meter basically showed the lights as consuming 0 watts. I left them plugged in for three days, and then measured the kilowatt hour consumption. I divided that by the number of hours plugged in (which the Kill A Watt meter tells you), and discovered that the total power draw of the string of 50 LED Christmas lights was a mere - ready for this? - 1.5 watts. To put that in perspective, if you were to leave these lights on 24 hours a day, 365 days a year, their total electricity consumption would be a mere =13.14 kWh, which represents about $1.60 worth of electricity. If you do leave your lights on continuously all year long, and your electricity comes 100% from coal, using solar LED Christmas lights instead of the plug-in LED Christmas lights I use, will save about 40 lbs of CO2 emissions.
It's the economy, stupid
But realistically you're not going to use your solar LED Christmas lights 24x7 all year long. We only use ours in the darkest months of the year - December through March - and only from 6pm to 10pm - and then we hang them on the patio in the summer to light things up on weekend evenings for a few hours. All told it works out to under 600 hours total, or about 1 kilowatt hour of use through the year (about $0.15 in electricity). And these are very bright lights compared to what you'll be getting if you buy solar LED Christmas lights.
Does it really make sense to pay $20 to $80 to save that small an amount of electricity? Especially given the number of customers who have complained about the low light output and poor reliability of this class of Christmas lights? You'd probably be more satisfied with the brighter light output of regular plug-in LED Christmas lights, at a much lower purchase price.
Instead, consider buying some inexpensive plug-in LED Christmas lights, and using the money you save to buy something else that will have a big payoff in terms of saving you energy. For example, the Kill A Watt meter I mentioned above is now available for only around $20 - I spent $100 on mine a few years back, and it has paid for itself many times over, because it helped me identify where I was using the most electricity and where I could find the most savings. Even spending $20 on weatherstripping for a froot door, or a plastic window insulation kit to reduce heat loss through an old window or porch door, will make a much bigger difference in terms of your household energy use, than buying solar LED Christmas lights.
Then again, it can be fun to own something that provides all its own power and gives a little sparkle of light to a garden, an arch trellis, a tree. In a way, solar LED Christmas lights are a good thing from an environmental perspective in that they help make more people aware of both the benefits and the limitations of solar power. Buy some solar-powered LEDs this year. But I would recommend something a little more practical - and more sturdily built - if you're just interested in getting into solar-powered lighting. For example, there are very well-built solar-powered outdoor security lights or shed lights that get very good customer reviews, are designed for use year-round, and are durable and long-lasting.
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