Solar panels are pretty straightforward. You put them on your roof, or your RV, and then you can ride off into the sunset, saving the Earth by using clean energy. But there are different types of solar panels with varying weights, which means you will want to consider every option before slapping some on your house.
There are three main types of solar panels, each with its own average weight. The most lightweight type of solar panel is called a thin-film solar panel, but it is also the least efficient type. Most roofs should be able to handle the weight of all solar panel types.
Solar panels are based on relatively new technology (the first model was developed in 1954), and as such, there are still new types coming out constantly. Companies are continuing to innovate, so keep reading to learn more about the traditional and brand-new solar panels (and how their weight will affect your house).
How It Works and Three Main Types
Solar panels have three main types: monocrystalline, polycrystalline, and thin-film. Unsurprisingly, the thin-film solar panels are exactly how they sound; thin. But the difference between each type of solar panel is much more than just weight variation.
Two of the main types of solar panels (monocrystalline and polycrystalline) are some of the most common types of solar panels used today. They also fall on the heavier end of the spectrum. These two types of solar panels are both made using silicon (which weighs 2.33 grams per cubic centimeter), which isn’t a particularly heavy element, but the way it’s used can add up to make solar panels weigh up to forty or fifty pounds.
The reason silicon is used in the production of solar panels is due to the photoelectric effect. The photoelectric effect is a phenomenon “in which electrically charged particles are released from or within a material when it absorbs electromagnetic radiation” (according to Britannica’s website). In other words, when certain atoms are hit by photons (electromagnetic radiation), the energy of the photon is absorbed by the electrons that are buzzing around the nucleus. On their own, they don’t have enough energy to escape the hold of the nucleus, but with the extra energy from the photon, the electrons can leave the atom and zip around wherever they want. This creates a flow of current and energy, which is what the solar panels charge up.
Solar panels utilize this effect by absorbing photons directly from the sun and using them to “set free” a bunch of electrons in the silicon atoms, therefore starting the flow of electrons, conducting electricity right through the solar panel inverter and to your house or RV. Silicon is used for this process because it is a semiconductor and it is extremely efficient for the photoelectric effect.
Monocrystalline solar panels are made by individual ingots (pure silicon crystals) that have been sliced into thin wafers, called solar panel cells. They are all lined up to create a finished solar panel. Since each wafer is sliced off of an individual crystal, these cells each have rounded edges.
Polycrystalline solar panels are also made from silicon, but instead of being made from pure silicon crystal, polycrystalline cells are made from fragments of silicon crystal that have been melted together, hence the name polycrystalline instead of monocrystalline. These solar panel cells are rectangular-shaped since they aren’t being sliced off a pure, rounded silicon crystal.
Both monocrystalline and polycrystalline solar panels weigh about nineteen kilograms (about forty-two pounds) per each sixty-cell solar panel, and twenty-five kilograms (about fifty-five pounds) per seventy-two-cell solar panel. Since they’re made of the same substance, (even though it’s arranged differently) they weigh almost exactly the same.
Thin-film solar panels include a variety of different types, so their weight range varies a lot, but overall, they weigh much less than the crystalline types of solar panels. These solar panels are made from a bunch of different materials (most commonly used is cadmium telluride, or CdTe) that are laid out in layers up to twenty times thinner than the crystalline cell wafers.
These solar panels can weigh a lot if they have a mounting system used to attach them to a roof, but oftentimes, they can be laid out directly on roofs, removing a need for extra weight altogether.
The structure of these solar panels also alters weight. There are two different types of solar panel structures:
- Flexible Solar Panels
- Rigid Solar Panels
Both of these structures are used in tandem with each type of solar panel, so there can be rigid thin-film solar panels or flexible monocrystalline solar panels. The structure is pretty much self-explanatory; flexible solar panels are flexible and can usually be stuck right on any surface, and rigid solar panels are brittle. They need to be held up with mounting systems because they won’t adhere to any surface.
Unsurprisingly, flexible solar panels don’t need mounts, so they will weigh less. Rigid ones will weigh more because of the added weight of mounting systems used to hold them up.
Weight Vs. Efficiency
Here’s a good rule of thumb to use when looking at solar panels:
Heavier solar panels are more efficient, and lighter solar panels are less efficient.
The weight and efficiency are, generally speaking, directly related. That means that if the weight is higher, the efficiency will be as well. So while you might prefer having a lighter solar panel system for your roof, the trade-off is, it won’t be nearly as efficient.
According to Sage Journals online, monocrystalline and polycrystalline solar panels have average efficiency ratings of fifteen percent, while thin-film solar panels have efficiency ratings of about ten percent. Sure, buying thin films might be cheaper and give you peace of mind about your roof, but will you get your money’s worth?
That five percent difference might not seem like a lot, but it’s actually a huge amount. In some cases, that fifteen percent efficiency can power entire houses, so losing five percent of that can make a huge difference.
Weight on Roofs
All of this information leads up to the final question; can my roofs handle the weight? This is a valid question: what if you wake up in the middle of the night to find that your roof is now a giant, caved-in pit, and your paid-off house has become a treasured memory?
Luckily for you, the danger with solar panels does not lie in their weight. There are almost no recorded cases of solar panels ever breaking the roof from weighing too much. If anything, there’s a much higher chance that the solar panel installation team will install them improperly and cause a leak in your roof than your solar panels actually weighing enough to break through the ceiling.
Roofs are able to withstand a lot of weight (about twenty pounds per square foot, or ninety-seven kilograms per square meter), and the heaviest solar panels don’t even come near hitting half of that weight. Mono- and polycrystalline solar panels weigh about two to four pounds per square foot (four to twenty kilograms per square meter). Since the roof can handle twenty pounds per square foot, those four pounds won’t weigh nearly enough to do anything to the infrastructure and integrity of your roof. Even if you got on your roof with the solar panels on top and started jumping, the worst it could do is make some dust fall through to your kitchen.
And thin-film solar panels won’t get close to doing any damage to your roof. They weigh about 0.4 pounds per square foot (two kilograms per square meter), so it’s safe to say that if you get some thin-film solar panels, they won’t be able to break your roof, even if they tried.
If your roof is just unstable, or if you live in an old house that you’re pretty sure once belonged to the Addams Family, you might not want to risk putting anything on top of it. We can’t blame you. Solar panels don’t break through sturdy roofs, but the only way to know if your roof is sturdy or not is by testing it. Once you find out that your roof really can’t sustain the weight of a couple of solar panels, it might be too late.
One solution to your problem might be to bypass the solar panel route altogether and get a solar roof instead. Solar roofs are like peanut butter cups–they put together two really good concepts into one. Instead of having solar panels mounted atop a sketchy roof, you can just cut out the middle man and just get a new roof that is made with solar panel capabilities.
The solar shingles used to make these solar roofs weigh less than solar panels, at about thirteen pounds per square foot (sixty-three kilograms per square meter) and while that seems heavy, their weight won’t be added on top of another row of shingles–they will be the shingles. As long as you don’t get an unholy amount of snow piled atop your roof this year during the holidays, your roof will be just fine.