Mixing Different Wattage Solar Panels

Solar power is becoming more and more popular as a form of renewable energy. But to get the most from your solar energy installation, it is key that you understand the basic principles that are behind it. 

One of the most common questions we get is whether mixing different wattage solar panels is possible. Today, we address this question so that you can understand your options when it comes to installing different solar panels. 

We’ve simplified this search for you with a clear and factual dos and don’ts approach to mixing different wattage solar panels. In our guide below, we explain how it affects your energy output, why it matters, and what you can do to make the best of what you have.

Our Guide to Properly Mixing Different Wattage Solar Panels

Is Mixing Different Wattage Solar Panels Possible?

Have you purchased a 200-watt solar panel, and wondered if it can be used with your old 100-watt panel? The short answer is, yes, you can mix solar panels that have different wattages. But it is not usually advised, because mixing different wattage panels reduces the efficiency and power output. 

Wattage Mixing Reduces Efficiency and Power

The reason for this is simple. Different wattage panels have different voltage and amps outputs. The system always favors the lowest voltage or amp, which puts the larger panel on the backburner. This, in turn, reduces the overall efficiency and power output of your solar panel array.

From sailboat solar panel installation to residential panels to installing solar panels on a van, certain basic electrical rules apply. So yes, they can be used together. But to mix different wattage solar panels, it’s crucial that you first understand the correct way to do it. 

Wattage Mixing Determines the Wiring System

A solar panel’s wiring is connected either in series or parallel. Normally, you don’t have to pay attention to these details, but if you’re dealing with mismatched wattage, the wiring system that you choose becomes important. 

The golden rule is that the same voltage should be connected in parallel, whereas the same current should be connected in series. But what’s the reason behind this rule? To understand this, we need to have a brief look at the two types of wiring connections.

Series vs Parallel Connections

Wiring Solar Panels in Series

How to Connect Panels in Series

To connect solar panels in a series, you connect the positive wire of each panel to the negative wire of the next and vice versa, alternating in this way. 

Advantages of Wiring in Series

Most residential solar panels are connected in series. When you connect solar panels in series, the voltage adds up, but the current stays the same. You can get away with smaller wiring and have a long run between the panel and the inverter without much loss of electricity. 

The Disadvantage of Wiring in Series

The general drawback with this type of wiring is that if one panel is in shade or goes out, the whole system becomes less effective. 

Different Wattage Solar Panels Wired in Series

If mixed wattage solar panels are connected in series, the total voltages are added. But the amps are reduced to the current of the lowest panel.

Wiring Solar Panels in Parallel

How to Connect Panels in Parallel

To connect solar panels in parallel, connect all of the positive wires together. Do the same with the negative wires. Be sure that you are using the right wires before connecting the panels. 

The Advantage of Wiring in Parallel

When you connect solar panels in parallel, the amps (current) increase but the voltage doesn’t. This usually suits the greater battering charging needs of off-grid solar users. 

Disadvantages of Wiring in Parallel

A parallel setup requires a heavier wire to handle the higher current. You also need more wire to make all the connections. 

But if you’re confused about what size cable to use for a 12v solar panel, or any other electrical issues, rather consult the experts.

Wiring Different Wattage Solar Panels in Parallel

If mixed wattage solar panels are connected in parallel, the total amps are added, but the voltage of the system reduces to the voltage of the lowest panel.

A Combination of the Two

You could choose a combination of series and parallel circuits to benefit from the advantages of both. To do this, first, connect the solar panels in a series and then join the strings in parallel. 

A simpler solution is to install microinverters to optimize each solar panel individually. This helps to avoid the problem of power loss due if one of the panels in the system is in shade. 

The Best Wiring for Mismatched Panels 

If you connect solar panels without matching either the amps or voltages, efficiency will be drastically reduced. If your solar panels are not matched in size, the system will always choose the lowest value.

This is especially crucial for panels connected in parallel. But whether wired in series or in parallel, this holds true. Plugging in a solar panel of a lower power rating into your array will reduce the total energy output. 

Mismatched Panels in Series

Solar panels connected in series add to the voltage. The amps will not change. But mismatched solar panels connected in series will choose the lowest amp among the solar panels.

Mismatched Panels in Parallel

Solar panels connected in parallel add to the amps. The voltage doesn’t change, but mismatched solar panels connected in parallel output the lowest voltage among the solar panels 

If the Solar Panels only Have Different Wattage  

You can wire solar panels with different wattages in parallel if they have similar voltages, but efficiency will drop. If they each contain a diode to prevent reverse current, you can safely connect them in parallel. 

This diode allows the current to flow in only one direction. Alternatively, install a micro inverter.

Wattage Dos & Don’ts 

Do These

• Stick to the same wattage if possible
• When the wattages differ, stick to the same voltage
• If wattage differs, but voltage matches, wire panels in parallel

Don’t Do These

• Don’t mix the voltages whenever possible 
• Don’t arrange the panels in parallel if the voltage differs
• Don’t proceed if you are unsure of what to do

Other Factors that Affect Your Solar Power 

Batteries 

You’ll probably need just one solar battery to keep the power on when the grid is down, but you’ll need greater storage capacity for a fully off-grid installation. This is where the batteries you choose can make a big difference.

Using Mismatched Batteries 

You may be aware of how to set up solar panels off-grid. If you’re tempted to mix different batteries when trying to achieve this greater storage capacity, keep the following in mind: Always avoid different types of batteries and batteries of different ages.

Risk of Overheating 

Mixing different capacity batteries for solar panels is not recommended. This is because batteries' performance levels change as they age. When the stronger battery in the system compensates for the weaker ones, there’s a risk of overheating which degrades your batteries faster and increases the risk of fire. 

For best results, always start with the same type of batteries of equal capacity, if possible.

Inverters

Another important factor to consider when installing solar panels is the inverter. 

String Inverters

Residential solar panel arrays are often accompanied by inverters. A string inverter is the most common. It aggregates the power output of your solar panels.  

Micro Inverters

But microinverters help to make your solar panel system far more efficient. They also handle panels being in shade, better. This will help to avoid the problem of power loss when a panel is not in full sun. 

Mixing Different Wattage Solar Panels FAQ 

Will my solar panel installation fail an inspection if different wattages are used together? 

The wattage of your solar panel does not affect the outcome of an inspection. 

There’s more chance of failing a solar inspection because of incorrect wires being used, as this can be dangerous. But if everything has been installed correctly, and all the wiring is correct, you’re good to go. 

Is it dangerous to mix solar panels of different wattages? 

It’s not dangerous to mix different wattage panels, but a loss of overall power is guaranteed. This affects your solar array’s productivity. So whenever possible, avoid mixing different wattage solar panels to avoid this problem. And when you have to use different wattage panels, follow our tips above.

Closing Thoughts 

Our mission is to make understanding and using solar energy simple. Always remember that while solar energy is harnessed from the sun, any electrical installation must follow certain basic rules to be both safe and efficient.

You will now understand the basics behind connecting solar panels, and how mismatched panels affect efficiency. So while mixing different wattage solar panels is not advised, it can be done if you follow the tips in our guide above.

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