Getting Familiar With Residential Rooftop Solar Panels

Roofing
Solar Energy
By Dikran Seferian November 22, 2021

The increasing demand for renewable energies has caused the solar panel market to skyrocket all the way up to the sun. Over the past ten years, the industry for rooftop solar units has almost doubled in size. This remarkable surge is also due to federal support and overall awareness of the advantages that clean energies provide. To have a better understanding of the solar sector, you may want to familiarize yourself with what the industry has to offer — solar panels. Also referred to as photovoltaic panels or PV panels for short, solar panels are available in a variety of different types. These systems are either based on crystalline or thin-film technologies, each of which is characterized by different features. Getting acquainted with the characteristics will give you a solid grasp of what to expect when shopping for the best solar panels for your house.

Types of Solar Panels

Four main types of photovoltaic panels exist in the market nowadays. Each of these solar units offers different properties in terms of efficiency and capacity. Moreover, you can find them at a wide range of prices. Make sure to consider every factor when choosing a solar panel for your rooftop.

Monocrystalline

Pros and Cons of Installing a Single-Crystal Solar Panel

Pros and Cons of Installing a Single-Crystal Solar Panel

Also referred to as single-crystal panels, monocrystalline panels are composed of single pure silicon crystals divided into several wafers. Due to their composition, you can identify the panels by their dark black color. Moreover, the pure silicon allows the single-crystal panels to last longer than the other solar panel types.

Efficiency 

Besides the longevity it provides, the composition of monocrystalline panels also makes them highly space-efficient. Single-crystal systems boast an efficiency rating of over 20%.

Capacity 

The single-crystal composition of monocrystalline cells gives them the highest power capacity in addition to a greater output rating within a more compact package. Most single-crystal cells can produce a power capacity of up to 300w.

Price 

The high efficiency, as well as the capacity of monocrystalline panels, come at a cost. A great deal of silicone is wasted in the manufacturing of one single-crystal cell. In many cases, the waste amounts to almost 50%. The price of monocrystalline can therefore be somewhat on the expensive side. You can expect to pay an average of $1 to $1.50 per watt.

Polycrystalline

As the name suggests, polycrystalline cells are made of several silicon crystals which are melted and poured into the square-shaped mold. This composition allows the panels to be much easier on the wallet as the wastage is minimal — besides giving them their characteristic shapes.

Getting Familiar With Polycrystalline Solar Cells

Getting Familiar With Polycrystalline Solar Cells

Efficiency 

The lower silicon purity level of polycrystalline — compared to that of monocrystalline — makes them less efficient when it comes to energy conversion as well as space. Their heat tolerance levels are also low, making them less efficient in hot environments. Polycrystalline cells have an efficiency rating of 15% to 17%.

Capacity 

Developments in solar technology have boosted the capacity of polycrystalline cells to range between 240w and 300w for a standard 60-cell unit. While this narrows the gap with monocrystalline, the latter still maintains its superiority.

Price

Polycrystalline units are more budget-friendly due to their simple production method and lower cost of production. This is because leftover crystal fragments are used from monocrystalline production. The average cost of polycrystalline panels is $0.70 to $1 per watt.

Passivated Emitter and Rear Cell

Abbreviated as PERC panels, passivated emitter and rear cell units are upgraded versions of the monocrystalline panel. This developed technology introduces a passivation layer in the backside of the cell, allowing it to work more efficiently. PERC units collect more solar energy in a smaller material footprint; this makes them perfect for compact spaces.

Benefits of Investing in a PERC Solar Unit

Benefits of Investing in a PERC Solar Unit

Efficiency 

The upgrade that PERC panels provide adds an extra 5% to the efficiency rating of monocrystalline units. This brings the total rating to over 25%.

Capacity 

PERC manufacturers claim that the units offer a capacity of 370w to 395w. This boost in capacity is mainly due to the introduction of the passivated layer, in addition to other improvements in solar technology.

Price

The production cost of PERC units is slightly higher than that of traditional cells — but mainly because of the additional materials that go into the process. The cells, however, can be constructed on the same equipment. This efficient manufacturing allows for a lower average cost per watt — $0.32 to $0.65 on average.

Thin-Film

Thin-film solar panels consist of fine layers that are as thin as a sheet of paper, which allows them to be flexible. The panels are also lighter since they don’t need a frame backing. This ultimately makes them easier to install. As opposed to crystalline panels which come in standard sizes, thin-film units are available in a variety of sizes.

While crystalline cells use silicon, thin-film panels are composed of three different materials — cadmium telluride, amorphous silicon, and copper indium gallium selenide.

  • Cadmium telluride (CdTe) has the lowest carbon footprint out of all the solar unit types. It also requires less water and has a lower energy payback time than other panels. Cadmium, however, is a toxic material and therefore more expensive to recycle. 
  • Amorphous silicon units (a-Si) get their name from their formless nature. An a-Si panel only requires a small portion of the silicon which goes into producing traditional silicon units. This results in a remarkably low cost of production.
  • Copper indium gallium selenide panels (CIGS) use a thin layer of each of the four elements placed on a plastic or glass backing. This combination allows CIGS units to be more efficient than the other thin-film panels — however, they still don’t match the efficiency of the crystalline types.
Everything You Need to Know About Thin-Film Panels

Everything You Need to Know About Thin-Film Panels

Efficiency 

Cadmium telluride panels have an efficiency rating of 9% to 11%, whereas CIGS units are slightly more efficient with a rating of 13% to 15%. Amorphous silicon cells, on the other hand, are the least efficient of all — having a rating of 6% to 8%.

Capacity 

There is no standard way of measuring the power capacity of thin-film units. This is mainly because they don’t come in standardized sizes. Thin-film panels will differ in capacity from one another according to physical size. In any case, traditional crystalline units will offer more capacity than a thin-film counterpart of the same dimensions.

Price

While CIGS panels don’t require you to break the bank, they have the highest cost per watt among the thin-film variety (averaging at $0.60 to $0.70 per watt). Lower on the price spectrum is cadmium telluride, with an average cost of $0.50 to $0.60 per watt. The most inexpensive type, however, is amorphous silicon with only $0.43 to $0.50 per watt on average.

Other Factors to Consider When Choosing Solar Panels

While price, efficiency, and capacity are key factors in selecting the solar unit that suits your needs, other elements are also worth considering. Accounting for all the factors that come into play will allow you to make the best choice.

Installation

Installing residential solar panels can cost anywhere between $9,000 and $28,000, with an average of $18,000. The price essentially depends on several key factors, most considerably the labor cost and demand in your area. Other elements include your energy usage, local solar unit prices, and the yearly amount of sun your rooftop receives. In any case, installing solar units will give you a significant return on investment in the long run. 

Temperature

A solar unit’s temperature can influence its ability to produce energy. This effect is indicated via the temperature coefficient which measures the output reduction for every 1℃ increase in heat level over 25℃ (77℉, but the coefficient is measured in Celcius). The temperature coefficient of crystalline panels ranges between -0.3% and -0.5% per ℃ while that of thin-film units is -0.2% per ℃. Basically, a thin-film system can be the ideal option if you live in warmer areas that receive more sunlight.

Space

In dense areas where every bit of space counts, monocrystalline units can be a good choice as they are highly efficient and tend to maximize utility savings. You can also go for PERC systems as they reduce long-run energy costs even more. If you live in a larger property, however, polycrystalline is the better option. Essentially, the larger surface area will make up for the reduced efficiency. You may want to bear in mind, however, that a larger footprint entails higher costs of labor. Thin-film solar systems, on the other hand, are more preferable where labor-intensive applications of crystalline units are not very practical. Such places can include apartment buildings and other compact spaces. 

Weather Conditions

Another important factor to consider when choosing a solar panel system is its hail rating. Solar cells are often tested for hail impact — this is usually done by dropping 2-inch steel pellets on solar cells from a height of over 50 inches. Due to their thick surface, crystalline units are resistant to hail storms of up to 50 mph. Thin-film panels, however, have a lower rating as they are thin and flexible.

Written by
Dikran Seferian

Written by Dikran Seferian