Can you Mix Mono and Poly Solar Panels? The Detailed Guide

Yes, you can combine monocrystalline and polycrystalline solar panels as long as they have similar electrical characteristics and are connected properly in an array.

Some strategies for combining these panels include connecting panels in parallel or series, selecting panels with similar voltage and current ratings, and ensuring that all the panels are facing the same direction and angle.

When combining these panels, it's important to consider their mathematical properties, such as their voltage, current, power, and efficiency ratings, as well as their compatibility with one another. It's advised to wire mono and poly solar panels in distinct strings for maximum output.

According to the mismatch rule, the voltage and short circuit current difference between the two types of solar panels should be less or equal to 25% to allow for mixing without power loss.

Combining monocrystalline and polycrystalline for improved performance requires a strategy and that’s exactly what we’ll discuss in this post.

Generally, when connecting solar panels, you’ll do it in strings. Each string has several solar panels and should be connected to a Maximum Power Point Tracker (MPPT), for output monitoring.

Every inverter has an operating range (the input range) at which it’ll best operate at. Additionally, it’ll have a maximum power point which will be the maximum net power it’ll work with without damage.

More on this later, but here is how these ratings relate to our topic:

If you combine mono and poly in the same string, there’s a high possibility that the output will be lower than the inverter’s operating range due to electrical characteristic differences.

When there’s insufficient power going into the inverter, it’ll not power on, and you’ll not get the juice you need to power up your devices.

However, combining monocrystalline and polycrystalline solar panels (each type in a distinct string) gives you the capacity to monitor the output rating, not to mention that fluctuations will barely occur.

In this case, the inverter will operate as intended and you’ll have the power you need from your system.

However, this is still a generalization, but we'll have a practical example later to show you how you should go about the mix-and-match process of mono and poly solar panels.

Monocrystalline vs. Polycrystalline Panels

Monocrystalline solar panels are made from a single, high-purity silicon crystal, while polycrystalline solar panels are made from multiple silicon crystals.

Monocrystalline panels have a uniform black appearance, while polycrystalline panels have a speckled blue appearance.

Monocrystalline panels are generally more efficient than polycrystalline panels, meaning they can generate more power for a given amount of space. However, monocrystalline panels are also more expensive to produce than polycrystalline panels.

One of the main differences between monocrystalline and polycrystalline panels is their cell structure.

Monocrystalline cells are made from a single crystal, which allows for more efficient electron movement through the cell.

Polycrystalline cells are made from multiple crystals, which can result in less efficient electron movement due to the boundaries between the crystals.

However, recent advancements in polycrystalline cell technology have narrowed the efficiency gap between the two types of panels.

Matching Electrical Characteristics

When combining monocrystalline and polycrystalline panels, it's important to match their electrical characteristics as closely as possible.

This includes their voltage and current ratings, as well as their temperature coefficients.

Voltage and current ratings describe the amount of voltage and current that a panel can produce, while temperature coefficients describe how a panel's performance is affected by changes in temperature.

One strategy for matching electrical characteristics is to select panels from the same manufacturer and product line.

This ensures that the panels have similar electrical characteristics and will work well together in an array.

However, if it's necessary to mix and match panels from different manufacturers or product lines, it's important to carefully consider the electrical characteristics of each panel.

Connecting Panels in Parallel

Connecting panels in parallel means connecting the positive terminals of all the panels together and connecting the negative terminals together. This creates a larger current output, but the voltage output remains the same as that of a single panel.

When connecting panels in parallel, it's important to make sure that they all have the same voltage rating, or else the voltage output of the array will be limited by the lowest voltage panel.

One strategy for combining monocrystalline and polycrystalline panels in parallel is to select panels with similar current ratings but different voltage ratings.

For example, if you have a monocrystalline panel with a voltage rating of 36 volts and a current rating of 8 amps, and a polycrystalline panel with a voltage rating of 30 volts and a current rating of 10 amps, connecting them in parallel can increase the overall current output without affecting the voltage.

Connecting Panels in Series

Connecting panels in series means connecting the positive terminal of one panel to the negative terminal of another panel.

This creates a larger voltage output, but the current output remains the same as that of a single panel. When connecting panels in series, it's important to make sure that they all have the same current rating, or else the current output of the array will be limited by the lowest current rating panel.

One strategy for combining monocrystalline and polycrystalline panels in series is to select panels with similar voltage ratings but different current ratings.

For example, if you have a monocrystalline panel with a voltage rating of 36 volts and a current rating of 8 amps, and a polycrystalline panel with a voltage rating of 36 volts and a current rating of 10 amps, connecting them in series can increase the overall voltage output without affecting the current.

Dealing with Challenges

One challenge of combining monocrystalline and polycrystalline panels is their different cell structures.

Monocrystalline cells are generally more efficient than polycrystalline cells, which can lead to inefficiencies when the panels are combined.

However, recent advancements in polycrystalline cell technology have narrowed the efficiency gap between the two types of panels.

Another challenge of combining panels is the potential for mismatched electrical characteristics. Mismatched panels can lead to inefficiencies and decreased performance in the solar array.

To mitigate this risk, it's important to carefully select panels with similar electrical characteristics and to monitor the performance of the array over time.

How to combine mono and poly solar panels?

Step 1: Determine the Number of Mono and Poly Solar Panels

To determine the number of mono and poly solar panels you need, you must know the electrical characteristics of your inverter.

A qualified solar technician can help you with this task. They can determine the number of mono and poly solar panels your inverter can work with based on their electrical characteristics.

Step 2: Choose Mono Solar Panels of Similar Electrical Characteristics

Once you know how many solar panels you need, the next step is to choose mono solar panels of similar electrical characteristics. You must choose solar panels with the same voltage and current rating and wire them to form a string.

Step 3: Do the Same for the Poly Solar Panels

You must also choose poly solar panels of similar electrical characteristics and wire them to form a string. It's important to remember that you cannot mix mono and poly solar panels in the same string.

Step 4: Check for Mismatch

If you still need to mix the solar panels in a single string, you must check for a mismatch.

The easiest way to do this is to take the current/voltage rating of the lowest-rated panel, divide it by the current/voltage rating of the highest-rated panel, and then subtract the answer from Step 1. The final figure should not be greater than 0.25 or 25% for compatible mixing to be achieved.

For example, let's say the solar panel with the highest rating is 8.0A while the lowest is 3.0A. In this case, 3.0/8.0 = 0.375.

When you subtract 0.375 from 1, you get 0.625. Since the final figure is greater than 0.25, these solar panels will lead to power loss if wired in the same string.

Even if they are both mono or poly solar panels, they should not be wired in the same string.

On the other hand, if the maximum current rating is 8.0 and the lowest current rating is 6.4, you can calculate the final figure by dividing 6.4 by 8.0, which is 0.8.

When you subtract 0.8 from 1, you get 0.2. Since the final figure is below 0.25, the panels can be combined in the same string, even if they are a mix of mono and poly solar panels.

Step 5: Connect Each String to a Charge Controller or String Inverter

Once you have chosen the solar panels and checked for mismatch, the final step is to connect each string to a charge controller or string inverter.

Tips to Consider When Combining Mono and Poly Solar Panels

1. Go for the correct configuration of the solar panels.

There’re two main wiring configurations for solar panels: series and parallel wiring.

• Mono and Poly solar panels in series- If you connect mono and poly solar panels in series, the current of all the panels should be the same. If otherwise (one solar panel has a very low current rating), the output current that goes to the inverter will be limited to the current of the lowest-rated panel.
• Mono and poly solar panels in parallel- In parallel, the voltage rating of the mono and poly solar panels should be the same or close to similar for maximum output to go to the inverter.

In either connection, ensure that you use high-quality wires and connectors so that there’s no power loss. For more details on this, check out our post on wiring solar panels in parallel or series.

2. Use an MPPT charge controller for each string

A maximum power point tracker helps monitor the output difference between the two types of solar panels if they're wired on different strings. Use an MTTP charge controller for each string to be on the safer side.

The good thing is, some modern string inverters come integrated with multiple MPPTs, so you don't have to buy them separately.

3. Wire mono solar panels in one string and poly panels on another

As a general rule, avoid mixing mono and poly solar panels in the same string to prevent output losses due to differences in electrical parameters.

Please note that, in this, we assume that all the mono solar panels have similar electrical parameters, the same as all your poly solar panels.

The Best Mono/Poly Strings Mixing Ratio

The maximum power ratio

If you’re looking to harness more power from the system, you should have more mono solar panel strings than poly solar panel strings. This ratio will also save on roof space since you'll use fewer solar panels.

The low-cost ratio

If the amount of power the system produces is not a significant concern, it’s okay to have more multi-crystalline strings than monocrystalline strings. Be ready to have enough roof space for this ratio.

Which is better? Mono or Poly Solar Panels?

No hard and fixed rule determines which of these solar panels is better. Instead, it depends on what you’re looking for as a consumer.

Pros and Cons of Mixing Mono and Poly Solar Panels

Pros

You enjoy the benefits of both types of solar panels.

You don't have to acquire expensive solar panels to meet your energy needs.

Cons

Possible output power loss if incompatible solar panels are wired together.

Many considerations go into determining the mixing compatibility, so installation can be time-consuming.

Wrapping up

While it’s recommended to use solar panels of the same electrical characteristics, you can mix mono and poly solar panels, following some guidelines.

If you want to mix mono and poly solar panels, do it in different strings and ensure each has its own MTTP charge controller.

You can still do mono and poly solar panels in one string, but check for mixing compatibility through the methods shown in this guide.

Mixing mono and poly solar panels can increase the overall performance of the system when done right.