The disappearing polycrystalline solar panel

Not that long ago, homeowners had a choice between cheaper polycrystalline and more efficient monocrystalline solar panels. These days, monocrystalline has taken over.

Credit: Zbynek Burival/Unsplash

Most solar panels on the market today as made with silicon. There are two types: polycrystalline and monocrystalline silicon.

To make monocrystalline solar cells, a single large crystal is grown. In contrast, polycrystalline silicon is made from small crystals that are formed into a larger ingot. With both types, the silicon is sliced into thin wafers to make individual silicon cells.

Growing a large crystal of silicon is a more difficult process, which is why monocrystalline solar panels have traditionally been more expensive. The advantage of that increased expense is higher efficiency compared to polycrystalline panels.

As recently as a few years ago, a homeowner would be faced with a choice between mono and poly panels. When it came to the cost-benefit analysis, often the lower cost of poly outweighed its lower efficiency, which has the disadvantages of higher labor costs (because you need to install more panels to achieve the same output), more supporting hardware (like racking and inverter components), and taking more roof space.

These days, things have changed a lot. The market share of poly solar panels has shrunk to only about 2% of the residential market. In utility-scale installations, poly panels have about 11% of the market share. Here’s some data compiled by Berkeley Lab:

Module efficiency distribution (2021). Credit: Berkeley Lab
Credit: Berkeley Lab

The share of installations using poly panels is shown in the lighter colors. For all markets, the share of poly is small, and almost non-existent for residential.

That this is true even though hardware costs are a higher proportion of large-scale solar installations than with home installations (which might have fewer than a couple dozen panels) shows that even the lower price of poly isn’t enough to make them an attractive choice for solar projects.

Solar panel technology keeps getting better

One of the reasons for the decline of poly panels is that solar technology keeps getting better and prices keep dropping, shrinking the relative price advantage of poly panels.

You can see the result in the average efficiency of solar panels that are installed each year, which has been steadily increasing to a historic high of 20.1% efficiency in the residential market in 2021.

Module efficiency trends (2021). Credit: Berkeley Lab
Credit: Berkeley Lab

You can see in the bar charts that the market share of mono panels has increased quite dramatically in just the past few years. Back in 2002, poly panels dominated the market with about 90% of the home market.

Heterojunction panels, PERC cells, half-cut cells and bifacial solar panels are some of the technologies that have hit the market in the past few years, and each of them have helped to make solar panels more efficient and cheaper per watt.

As manufacturing volumes of panels with these technologies increases, the price drops too, further cutting into the price advantage that poly panels once held.

Should you even consider poly panels for your home?

If you have ever seen an older home solar installation that has panels with a shimmering blue color (like the ones pictured at the top of this article), it most likely is using poly solar panels. Mono panels have a dark or black color.

Should you consider poly panels for your home installation? Probably not. Even though recent inflation has paused or even reversed the trend of dropping solar panel prices, it’s still true that the solar panels themselves are a relatively small part of the cost of a home solar installation, and that cost will continue to shrink in the future.

Unless your installer is offering a large price difference for poly panels, it probably isn’t a good choice. Poly panels might be offered by more budget manufacturers, and with that comes a shorter warranty and the risk of lower reliability. The cost of repairing a failed panel could easily exceed any upfront cost savings you get.

Labor costs are proportionally higher for small solar installations, so it’s important to choose reliable hardware that will lower your risk of having to pay for an expensive service call some years down the line.

You can still find poly panels for the hobbyist market

One place where poly solar panels hasn’t disappeared is the hobbyist market. If you need a small solar panel for a DIY project, you can find plenty of cheap poly solar panels for sale. If you have a project where efficiency is less critical and you just need the cheapest product that works, a poly panel could be just fine.

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