Solar power is one of the most popular renewable sources of energy and is a critical component of reaching net-zero emissions by 2050.  As a homeowner, you may be considering solar panels to both offset your energy costs and lower your carbon footprint.  When researching your project, you will find that there are several types of solar panels, which can be confusing to those just starting out. Your solar installer will be able to guide you through this decision-making, but this guide is a great primer of the types of panels and options, so you know what to ask about.

Here’s what we’ll cover in this guide – feel free to jump to the section you’re interested in.

1. Photovoltaic vs Solar Thermal Panels
2. Connecting Solar to the Electrical Grid and Battery Storage
3. Types of Solar Panels
4. Solar Shingles and Solar Roofs
5. Cost of Solar Panels by Type

Photovoltaic vs Solar Thermal Panels

First off, there are two types of solar panels: photovoltaic (PV) and solar thermal. When most people think of solar, they think of photovoltaic panels, those that generate electricity.  But there is another popular option in solar: solar thermal panels (also known as solar collectors).  Solar thermal panels also capture energy from the sun, but don’t generate electricity, they heat water. The warm water can be used to heat a building or swimming pool.   

We won’t be covering solar thermal panels here.  This guide will focus on the types of photovoltaic solar panels but know that solar thermal panels are also a low-cost and reliable way of heating homes and pools.

Connecting Solar to the Electrical Grid and Battery Storage

When thinking about a solar system, one of the early considerations is whether you want to connect the solar panels to the grid, and whether or not you want to include battery storage in your system.  Here we’ll break down the three options:

Grid-Tied Solar – The most common form of solar installation is one that is tied to the electrical grid.  This allows the home to use solar, but not be 100% reliant on the sun shining, allowing you to draw power from the grid as needed.  This system is typically the lowest cost as it doesn’t require additional equipment that an off-grid system does.  Additionally, most states offer net metering which pays you or credits you for the electricity you generate above what you use.  Through net metering, you are pushing power into the grid and getting compensated for it.  One consideration of grid-tied solar is that if the grid experiences a power outage your solar system will typically stop working. Solar inverters are designed to shut off solar power in order to protect line workers as they work on restoring power.  These workers need to know that the power lines are not electrified due to homeowners’ solar generation.  In order to have sustained power during a power outage, you’ll want to include battery storage (discussed below) and ensure that your system has ‘islanding capabilities’ that allow it to disconnect from the grid in the event of a power outage.

Grid-Tied Solar With Battery Storage – Adding battery storage to your system has several benefits.  Outside of providing power during a blackout, a battery can also reduce your reliance on the grid when electricity rates are higher.  There is a push by some states to implement what’s called Time of Use (TOU) rates for electricity.  This means that you pay more for electricity during peak-use hours, often after the sun is lower in the evening hours and your panels are not generating as much power.  Drawing power from your battery during these expensive times can be a nice cost-saving measure.

Off-Grid Solar Systems – While it’s advisable in the majority of cases, it is not required to have your home tied to the electrical grid.  Off-grid solar systems are completely energy independent and are most commonly found in more remote locations.  These systems are more expensive than grid-tied systems for two reasons.  Firstly, off-grid systems need to be larger (both in terms of the number of panels and the battery storage) as you need to generate 100% of your energy needs.  This additional size drives up the cost of the off-grid system.  Secondly, many of the rebates from local utilities are not offered to off-grid systems, making the upfront costs higher.

Types of Solar Panels

Alongside inverters and batteries, the panels themselves are the biggest component of a solar system.  The solar industry is progressing at a rapid pace to develop more efficient and lower cost panels and now there are several options for the homeowner to consider when buying solar panels.  The main three types of photovoltaic solar panels are monocrystalline, polycrystalline, and thin-film, which we’ll describe below.  We’ll also explore an exciting development around solar panel efficiency called PERC.  Finally, we’ll describe the pros and cons of solar roofs, a newer entrant in the market.

Monocrystalline Solar Panels – Both mono and polycrystalline panels are made from silicon wafers which are arranged into a rectangular pattern, covered with a sheet of durable glass, and enclosed in a frame.  Monocrystalline panels differ from polycrystalline panels in that they are cut from a single sheet of silicone, as opposed to being assembled from multiple silicone fragments that are fused together.  Using a single sheet of silicon improves the efficiency of the panels, but also costs more due to the energy required to make the cells and the wasted silicon from the cutting process.  In terms of efficiency, monocrystalline cells can reach over 20% efficiency and cost between $1.00 and $1.50 per watt.  20% efficiency means that 20% of the sun’s energy that hits the panels is converted to usable electricity.  As you’ll see in the table above, 20% is near the top of the range in terms of efficiency available from today’s panels. Monocrystalline solar panels are a premium product and well suited for those with the budget to afford them, or for space-constrained installations.

Polycrystalline Solar Panels – As mentioned above these are constructed from silicon fragments that are fused to make the solar cells. In fact, the leftover fragments from cutting the single-sheet monocrystalline panels are often used to create polycrystalline panels. These panels are slightly lower efficiency at 15-17% efficiency (vs. 20%+ for monocrystalline) but also cost less at between $.90 and $1.00 per watt.  The panels are a solid option for those with a bit more space to install their system and want a more affordable solution.

Thin Film Solar Panels – These panels are made using different materials than mono and polycrystalline panels and have some distinct advantages and disadvantages. Per square foot, they are the least efficient at around 11% efficiency, but they are also the most affordable at between $.43 and $.70 per watt.  The efficiency of thin-film panels has also increased and will likely continue to.  Thin-film solar panels also are easier and cheaper to install and can be used on a larger variety of rooftops.

Passive Emitter Rear Cell (PERC) Solar Panels – This is an exciting development in solar technology that is gaining popularity as a simple way to boost the efficiency of mono and polycrystalline solar panels. PERC solar panels perform better in low-light and high-temperature conditions, another benefit.  PERC is the integration of a back surface passivation layer to the solar panel that increases efficiency in 3 ways. Firstly, the back surface layer reflects light back up into solar cells, giving them a second chance to generate power.  Secondly, PERC helps reduce ‘electron recombination’ which reduces panel efficiency. Simply put, electron recombination is the tendency for electrons that have been knocked off a layer of silicon by sunlight (a key step in generating power) to recombine, which prevents them from moving freely and being turned into usable power. PERC reduces electron recombination and increases panel efficiency.  Finally, solar panels are less efficient when they heat up, and PERC reflects heat-causing wavelengths of light, keeping the panels cooler and more efficient.  PERC panels are only slightly more expensive, but there are savings in other areas. For example, if you need fewer panels because of the increased efficiency, your installation and balance-of-system costs (wiring, inverters, etc) will be lower.  In general, PERC is a great option for most homeowners.

Solar Shingles and Solar Roofs

One of the newest types of solar panels are solar shingles and solar roofs sometimes referred to as building-integrated photovoltaics of BIPV.  Unlike traditional solar panels that are mounted on top of an existing roof, solar roofs replace your existing roof with shingles that have photovoltaic cells built into them.  The main reason people opt for solar roofs over traditional solar panels is aesthetics.  Either people prefer the look of not having solar panels, or in some cases, neighborhood HOAs have restrictions on solar panels.  It’s good to know, however, that many states have laws preventing HOAs from blocking you from putting solar on your house.

In terms of brands offering solar roofs, you’ve likely heard of the much-hyped Tesla Solar Roof, which, while looks great, has had several hiccups getting to market and is still not widely available.  Certainteed, a well-known roofing manufacturer also has solar shingles called the Apollo II and Apollo Tile II which are available nationwide through their installer network and are designed to work as an addition to your roof, not requiring a full roof replacement. SunTegra also has a somewhat unique low-profile solar option that replaces roof tiles.  After installing the SunTegra product your roof may have part SunTegra tiles and part original roof tiles.

One downside of solar shingles is that they are more expensive than traditional solar panels.  That said, if your roof is in need of replacement, replacing it with a solar roof may cost around the same as replacing it with a standard roof and adding solar panels.  Another downside of solar shingles is that they tend to be less efficient than traditional panels.  Solar roofs typically range from between 14-18% efficiency vs. over 20% efficiency for standard panels.

Cost of Solar Panels by Type

When deciding what type of solar panels are best for your needs, the cost will be a consideration.  While some panels cost more than others, they will be more efficient and save you more over the lifetime of your system  For full information on the costs of solar panels and systems, including tax rebates and incentives, please visit the Zwell Guide to Solar Panel Costs, Tax Credits, Incentives and Rebates.